Symposium Organizers
V. Prasad Shastri Vanderbilt University
Andreas Lendlein Institute of Polymer Research
LinShu Liu U. S. Dept of Agriculture
Samir Mitragotri University of California-Santa Barbara
Antonios Mikos Rice University
HH1: Advanced Biomaterials I
Session Chairs
Monday PM, December 01, 2008
Room 310 (Hynes)
9:00 AM - **HH1.1
Citric Acid-based Biomaterials: Teaching an Old Compound New Tricks.
Guillermo Ameer 1
1 Department of Biomedical Engineering and the Department of Surgery, Northwestern University, Evanston, Illinois, United States
Show Abstract9:30 AM - HH1.2
Dual and Triple Shape Capability of Poly(ε-caprolatone)dimethacrylate Networks with Dangling PEG Chains.
Marc Behl 1 , Ingo Bellin 1 , Andreas Lendlein 1
1 Center for Biomaterial Development, Institute of Polymer Research, GKSS Forschungszentrum Geesthacht GmbH, Teltow Germany
Show AbstractShape-memory polymers are an emerging class of functionalized materials, which are able to change their shape in a predefined way upon appropriate stimulation [1]. Therefore an attractive application area for shape-memory polymers is their use in active medical devices [2, 3]. Shape-memory polymer research was focused on the implementation of different stimuli for triggering the shape-memory effect [4]. All these systems are dual-shape materials, which can transform from a first shape (A) to a second shape (B). Recently, polymeric materials with a triple-shape capability have been introduced. These polymer networks are able to change from a first shape (A) to a second shape (B) and from there to a third shape (C) [5]. Here we highlight this new kind of polymeric triple-shape materials. As the triple-shape effect is a general concept, we will introduce suitable polymer architectures and their appropriate programming. While the permanent shape is determined by the chemical crosslinks formed during network preparation in these materials, distinct domains can be used to fix the two temporary shapes either by crystallization or vitrification. When programmed appropriately in a two-step thermomechanical process, these materials exhibit a triple-shape effect. Triple shape-memory polymers can also be functionalized like dual shape materials [6]. Here, the two switching domains formed by two different switching segments can be used either individually or simultaneously to fix the temporary second shape. In graft polymer networks with poly(ε-caprolactone) segments and poly(ethylenglycol) side chains, the switching temperature, which needs to be exceeded for inducing the shape-memory effect, correlates with the melting transition of the related domain, if one domain is used for fixation. If both domains are used, the switching temperature correlates with the higher melting temperature.[1]A. Lendlein, S. Kelch, Angew. Chem. Int. Ed. Engl. 41 (2002) 2034.[2]F. El Feninat, G. Laroche, M. Fiset, D. Mantovani, Adv. Eng. Mat. 4 (2002) 91.[3]R. Langer, D. A. Tirrell, Nature 428 (2004) 487.[4]M. Behl, A. Lendlein, Mater Today 10 (2007) 20.[5]I. Bellin, S. Kelch, R. Langer, A. Lendlein, Proc.Natl.Acad.Sci.USA 103 (2006) 18043.[6]I. Bellin, S. Kelch, A. Lendlein, J. Mater. Chem.17 (2007) 2885.
9:45 AM - HH1.3
Fluorescent Core-Shell Silica Nanoparticles as Probes for in Vitro and in Vivo Imaging and Sensing.
Andrew Burns 1 , Erik Herz 1 , Barbara Baird 2 , Jin Hyang Choi 3 , Gabriela Hidalgo 4 , Alexander Nikitin 3 , Len Lion 4 , Anthony Hay 5 , Michelle Bradbury 6 , Ulrich Wiesner 1
1 Materials Science & Engineering, Cornell University, Ithaca, New York, United States, 2 Chemistry & Chemical Biology, Cornell University, Ithaca, New York, United States, 3 Biomedical Science, Cornell University, Ithaca, New York, United States, 4 Civil & Environmental Engineering, Cornell University, Ithaca, New York, United States, 5 Microbiology, Cornell University, Ithaca, New York, United States, 6 Radiology, Memorial Sloan-Kettering Cancer Center, New York, New York, United States
Show AbstractAmorphous sol-gel derived silica has shown itself to be an excellent host material for functional nanoparticles, particularly for application as probes and sensors in biology and nanomedicine. The facile and versatile chemistry of silica allows architectures to be tuned to specific applications, as well as the incorporation of diverse functional groups including dyes, chelators, polymers and targeting moieties. Our earlier work demonstrated core-shell fluorescent nanoparticles containing a core of silica-bound dye molecules surrounded by a pure silica shell, which exhibit exceptional brightness and stability compared to the constituent dyes as a general trend for dyes across the UV/visible spectrum. These particles have been applied to address a wide variety of questions both in vitro, as well as in vivo investigating the biodistribution and application of these particles to clinically-relevant tasks including sentinel lymph node imaging. Further, this core/shell concept lends itself particularly well to the development of quantitative ratiometric sensors. The co-localizaton of reference and sensor dye molecules in separate layers of a core-shell particle yields quantitative sensors with high surface area for analyte interaction, while protecting the reference signal within. We have generated core-shell sensor particles with average radii below 6 nm, capable of delivering high local concentrations of pH or Ca+2 sensor dye to biological microenvironments and have applied them to multi-dimensional chemical imaging in a variety of biological systems.
10:00 AM - HH1.4
Optimised Synthetic Route for Tuneable Shell SiO2@Fe3O4 Core-Shell Nanoparticles.
Carmen Vogt 1 , Muhammet Toprak 1 , Jingwhen Shi 2 , Bengt Fadeel 2 , Stefan Brene 3 , Rouslan Sitnikov 3 , Mamoun Muhammed 1
1 Functional Materials, Royal Institute of Technology, Stockholm Sweden, 2 Institute of Environmental Medicine, Karolinska Institutet, Stockholm Sweden, 3 Experimental MR Center, Karolinska Institutet, Stockholm Sweden
Show AbstractNanoparticles are subject for intensive research activities as they find a large variety of applications in numerous biomedical fields from enhancement of image contrast in MRI to different magnetically controllable drug delivery systems. Size limitation (below 100 nm to avoid endocytosis by macrophages and to be able to pass internal biological membranes) is one of the most important factors when considering targeting different types of tissues / organs (among other factors i.e. surface coatings functionalisation/activation). Silica is one of the preferable materials for surface coating when high biocompatibility, stability and increase in residence time is desired. This investigation is on the optimisation of a synthetic route for tuneable shell thickness SiO2@Fe3O4 core-shell nanoparticles for biomedical applications. Water in oil microemulsion synthesis is a well known technique for producing monodisperse particles, however, the application of this technique in producing well-dispersed single core-shell nanoparticles in large quantities is still challenging. In this study we report on the synthesis of well-separated, monodisperse single core-shell SiO2@Fe3O4 nanoparticles with an overall diameter of ~30 nm. The influence of different parameters (i.e. the nanoparticles size, nanoparticles concentration in the oil phase, the water/surfactant molar ratio, condensation time, etc.) on synthesis of tuneable shell thickness core-shell nanoparticles is reported. Particles’ cell toxicity and performance as MRI contrast agents were also undertaken due to their promising biological applications (as contrast agents, cell labelling and separation, drug delivery systems, etc.) and results are presented.
10:15 AM - HH1.5
Antimicrobial Nanostructured Hydrogel Webs with Controlled Silver Release.
Jian Wu 1 , Shuyu Hou 1 , Dacheng Ren 1 , Patrick Mather 1
1 Department of Biomedical and Chemical Engineering and Syracuse Biomaterials Institute, Syracuse University, Syracuse, New York, United States
Show AbstractWe have prepared new electrospun nano-fibrous scaffolds featuring excellent antimicrobial properties. Specifically, poly(ethylene glycol)(PEG)-based multi-block thermoplastic polyurethanes (TPUs) incorporating polyhedral oligomeric silsesquioxane(POSS) moieties were co-dissolved with silver nitrate(AgNO3) and subsequently electrospun to yield durable hydrogel webs capable of controlled silver ion release for effective antimicrobial behavior, which was analyzed quantitatively. Due to significant thermodynamic incompatibility between POSS moieties and ethylene oxide units, POSS nanocrystals, resulting from micro-phase separation, serve as physical crosslinking points within an inorganic-organic hybrid network, in turn affording novel hybrid organic-inorganic hydrogels in the water-swollen state. The resulting organic-inorganic hybrid hydrogel scaffolds not only feature excellent mechanical properties, but also display a desirable prolonged antimicrobial effect. For instance, our antimicrobial tests demonstrated that the electrospun nano-fibrous scaffolds (fiber diameter = 170±30 nm) prepared from TPUs incorporating 1.0 wt-% AgNO3 loading can effectively suppress Escherichia coli (E. coli) biofilm formation for 12 days, which is much longer than its cast (non-porous) film counterpart that suppressed E. coli biofilm formation for only 1 day. In contrast to conventional hydrogels, we observed that our electrospun nano-fibrous scaffolds hydrate with minimal change in macroscopic dimensions, perhaps due to a nano-confinement effect. We suggest that this arrested swelling behavior could enable us to control the rate of silver ion release from the electrospun hydrogel scaffold. We will discuss applications in wound dressing and reconstructive oral and bone surgery that can directly benefit from the properties of the new materials.
10:30 AM - HH1.6
Engineering Biomimetic Polymersomes for Effective Cytosolic Delivery.
Giuseppe Battaglia 1
1 Engineering Materials, University of Sheffield, Sheffield United Kingdom
Show AbstractOne of the most challenging aspects of drug delivery is the intra-cellular delivery of active agents. Several drugs and especially nucleic acids all need to be delivered within the cell interior to exert their therapeutic action. Small hydrophobic molecules can permeate cell membranes with relative ease, but hydrophilic molecules and especially large macromolecules such as proteins and nucleic acids require a vector to assist their transport across the cell membrane. This must be designed so as to ensure intracellular delivery without compromising cell viability. We have recently achieved this by using pH-sensitive poly(2-(methacryloyloxy)ethyl-phosphorylcholine)- co -poly(2-(diisopropylamino)ethyl methacrylate) (PMPC-PDPA) diblock copolymers that self-assemble to form vesicles in aqueous solution. These vesicles combine a non-fouling PMPC block with a pH-sensitive PDPA block and have the ability to encapsulate both hydrophobic molecules within the vesicular membrane and hydrophilic molecules within their aqueous cores. It is particularly noteworthy that PMPC-PDPA diblock copolymers form stable vesicles at physiological pH but that rapid dissociation of these vesicles occurs between pH 5 and pH 6 to form molecularly dissolved copolymer chains (unimers). We used PMPC-PDPA vesicles to encapsulate small and large macromolecules and these were successfully delivered intracellularly. Dynamic light scattering, zeta potential measurements, and transmission electron microscopy were used to study and optimize the encapsulation processes. Confocal laser scanning microscopy and fluorescence flow cytometry were used to quantify cellular uptake and to study the kinetics of this process in vitro and in vivo. We show the effective cytosolic delivery of nucleic acids, proteins, hydrophobic molecules, amphiphilic molecules, and hydrophilic molecules without affecting the viability of cells or even triggering inflammatory pathways.
10:45 AM - HH1.7
Single Component Polymer Capsules for Biomedical Applications.
Alexander Zelikin 1 , Siow Feng Chong 1 , Sri Sivakumar 1 , Amy Sexton 2 , Robert De Rose 2 , Stephen Kent 2 , Remy Robert 3 , Kim Wark 3 , Frank Caruso 1
1 Department of Chemical and Biomolecular Engineering, The University of Melbourne, Parkville, Victoria, Australia, 2 Department of Microbiology and Immunology , The University of Melbourne, Parkville, Victoria, Australia, 3 Preventative Health Flagship and Division of Molecular and Health Technologies, CSIRO, Parkville, Victoria, Australia
Show AbstractEncapsulation of drugs and reagents for diverse applications ranging from encapsulated catalysis and sensing to drug delivery requires the creation of colloidally stable nano- and micro-capsules. Among the requirements for a successful capsule, monodispersity in size ensures the uniform properties of capsules and the degradable nature delivers the means to recover the reaction product or, in the case of biodegradable capsules, deliver the cargo therapeutics. Within the size range from 300 nm to several microns, a promising technique to produce said capsules in high yield is the facile layer-by-layer approach, in which interacting polymers are sequentially deposited onto a sacrificial colloidal template to form a thin polymer film. The latter becomes the wall of the capsule upon dissolution of the core particle. In this work, we describe the preparation of monodisperse colloidally stable degradable polymer capsules with sizes as small as 300 nm. The capsules consist of chains of poly(methacrylic acid), PMA, crosslinked via biodegradable disulfide linkages and deconstruct in the presence of a physiological concentration of the intracellular reducing agent, glutathione, GSH. The first step in the preparation of disulfide stabilized PMA capsules is the sequential deposition of poly(vinyl pyrrolidone), PVP, and thiolated PMA, PMASH, on colloidal template particles such as silica, as it is commercially available as monodisperse samples with varied sizes. The linear build-up of polymer multilayers provides control over the thickness of polymer film, which then translates to the thickness of the capsule wall which, in turn, determines properties permeability and stability of the capsules. After the desired number of polymer layers was deposited, the thiol groups are converted into bridging disulfide linkages. Removal of the core particles produces hollow capsules, and transferring the capsules into pH 7 results in ionization of PMASH and release of PVP from the capsules wall. The resulting single component PMA capsules are stabilized via the disulfide linkages and remain intact in a wide range of pH; the capsules exhibit reversible swelling in response to external pH and remain colloidally stable over a range of physiologically relevant experimental conditions (e.g., in the presence of serum proteins).We demonstrate that the capsules and the constituting polymers are non-toxic, as verified by the cell viability and proliferation assays, and are effectively taken up by the cells of varied types and function. When loaded with lipophilic anticancer drugs, the capsules exhibit minimal passive release of the therapeutic and are effective in delivering the cargo to cause cell death. In the whole human blood, the capsules are taken up by white blood cells, including monocytes and dendritic cells, deliver the functionally active oligopeptide cargo to the antigen presenting cells and stimulate an immune response.
11:00 AM - HH1: ADBIOMAT
BREAK
HH2: Drug Delivery Systems I
Session Chairs
Monday PM, December 01, 2008
Room 310 (Hynes)
11:30 AM - HH2.1
Micelles for Delivery of Nitric Oxide.
Yun Suk Jo 1 , Jay Gantz 1 , André van der Vlies 1 , Tyler Thacher 1 , Sasa Antonijevic 2 3 4 , Simone Cavadini 2 , Davide Demurtas 5 , Nikolaos Stergiopulos 1 , Jeffrey Hubbell 1 2
1 Institute of Bioengineering (IBI), École Polytechnique Fédérale de Lausanne (EPFL), Lausanne Switzerland, 2 Institute of Chemical Sciences and Engineering (ISIC), École Polytechnique Fédérale de Lausanne (EPFL), Lausanne Switzerland, 3 Department of Chemistry, University of California Berkeley, Berkeley, California, United States, 4 Division of Materials Science, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 5 Centre Intégratif de Génomique, Université de Lausanne, Lausanne Switzerland
Show AbstractCoronary arterial atherosclerosis is closely related to endothelial dysfunction and pathophysiologically altered homeostasis. Surgically, PTCA is performed to restore blood flow and nutrient transport in occluded lesions. However, this interventional surgery can still cause another incidence, namely post-PTCA restenosis due to the mechanical stimuli of catheter or metallic stent to the intact endothelium. In order to treat post-PTCA restenosis, the importance of local drug delivery has been focused upon due to the limited success of systemically administrated pharmaceutical drugs. Endogenous NO generated from endothelial nitric oxide synthase (eNOS) induces endothelial-dependent relaxation of blood vessels and modulates the tone of arterial vascular smooth muscle cells (VSMCs). Thus, NO-releasing drugs, namely NO donors would be very interesting for various cardiovascular therapies. However, most NO donors are decomposed much too fast to properly act as an anti-restenotic drug, which would require NO release over a longer time frame, ca. a few weeks after deployment of stent. Despite a number of NO-releasing drugs developed thus far, their ultra-rapid decomposition rate in contact with water has been always a major obstacle before possible implementation as pharmaceutical agents. Taking these requirements into consideration, we conceived NO-releasing micelles, which (1) release NO in a sufficiently slow pattern, (2) are of favourable size (e.g. less than 100 nm), and (3) are self-assembled structures to be eventually secreted after all NOs are delivered. Amphiphilic block copolymers can be assembled into a specific supramolecular structure by thermodynamically driven process. Self-assembled micelles likewise are attributed in a core-shell structure and considered an ideal platform to deliver pharmaceutical payloads in a controlled rate. Here we present the formation of micelles directed by in situ reaction of pressurized nitric oxide (NO) gas with intact hydrophilic moiety of diblock copolymers, i.e. polyamines. In contact with water, worm-like micelles (diameter: 50-80 nm) reversibly release NO, a key signaling molecule in the body, during remarkably long time period, ca. over three weeks. NO-bound secondary amines are conserved in a hydrophobic core, protected from proton transfer, and thus acid-triggering hydrolysis is slowed down, which benefits us this strikingly long release pattern. Micelles infused into the rabbit artery ex vivo readily penetrate the arterial wall at which point their therapeutic aspects could be exploited, namely slow delivery of NO to restenotic lesions.
11:45 AM - HH2.2
Triterpene Saponin Glycosides: a New Class of Chemical Penetration Enhancers.
Christopher Pino 1 , Jordan Gutterman 2 , V. Shastri 1
1 Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, United States, 2 Department of Molecular Therapeutics, M.D. Anderson Cancer Center, Houston, Texas, United States
Show AbstractThe uppermost layers of the epidermis, the stratum corneum, provides the barrier properties to skin and plays a critical role in the regulation of the transport and retention of many important molecules, such as water, oxygen and sodium. Changes to the permeability of skin toward these molecules can seldom be achieved without altering the barrier function of skin. For example, an increase in evaporative water loss accompanies chronic skin conditions such as psoriasis and eczema. Triterpene saponin glycosides (TSGs) are a class of macromolecules that have been shown to interact favorably with synthetic lipid bilayers. Due to its size (several hundred Daltons), these molecules would be considered poor candidates for transdermal (TD) transport. We found that in spite of their molecular weight (MW) exceeding the theoretical cut-off for TD transport, TSGs exhibit appreciable percutaneous adsorption and transport through full thickness pig skin. Additionally, TSGs are also capable of enhancing the transport of both hydrophilic and hydrophobic compounds (Estradiol) without significantly impacting their partitioning behavior. This suggests that TSGs might be promoting TD transport of these molecules through secondary pathways that have been hitherto unexplored and may be used to modulate homeostasis.
12:00 PM - HH2.3
Structure and Mechanical Properties of Nucleic Acid Lipid Films and Their Application as Drug Delivery Vehicles Towards Human Breast Cancer Cells.
Surekha Gajria 1 2 , Thorsten Neumann 2 1 , Matthew Black 3 2 , Wirasak Smitthipong 2 3 , Luc Jaeger 1 2 , Matthew Tirrell 3 2
1 Chemistry, UC Santa Barbara, Santa Barbara, California, United States, 2 Materials Research Laboratory, UC Santa Barbara, Santa Barbara, California, United States, 3 College of Engineering, UC Santa Barbara, Santa Barbara, California, United States
Show AbstractNegatively charged nucleic acids such as RNA and DNA can self-assemble with cationic lipids via electrostatic complexation to form water-insoluble complexes capable of forming self-standing films when cast from an organic solvent such as isopropanol, as previously reported1,2. We have investigated their structure by X-ray scattering, X-ray reflectivity, and AFM, as well as their tensile strength and mechanical properties. If didodecyldimethylammonium bromide (DDAB) is chosen, the films have a lamellar structure of nucleic acid strands sandwiched between bilayers of the cationic lipid which are thought to be fully interdigitated. Since nucleic acids are able to intercalate certain drugs within their double helical strands, the films can act as local carriers for these drugs when placed in the vicinity of a diseased area, such as a tumor. One example of such a drug is daunorubicin, a drug commonly used in breast cancer therapy, which targets DNA replication in fast growing cells such as cancer cells. These drugs could be released by local enzyme degradation of the nucleic acid-lipid scaffold within the body while the remaining film components can be easily degraded to monomer units. We have also investigated the biodegradability and biocompatibility of the films and found them suitable for insertion within the body, particularly when blended with a neutral biocompatible biodegrdable polymer such as PEG, and the time and extent of degradation can be varied depending on the composition of the nucleic acid within the film. The films are fairly simple to prepare and can be produced on a large scale. We present these films as a novel type of biomaterial capable of mediated local drug delivery to human breast cancer cells rather than normal human breast tissue cells in vitro. 1.ljiro, K. and Okahata, Y. “A DNA-Lipid Complex Soluble in Organic Solvents.” J. Chem. Soc., Chem. Commun., 1992, 1339 – 1341.2.Hoshino, Y. et al. “RNA-Aligned Film Prepared from an RNA/Lipid Complex.” Macromol. Rapid Commun. 2002, 23, 253-255.
12:15 PM - HH2.4
IMAC Surface Modification of Polyketal Microparticles for Dual-Mode Drug Release.
Jay Sy 1 , Niren Murthy 1 2 , Michael Davis 1 3
1 Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology & Emory University, Atlanta, Georgia, United States, 2 Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, Atlanta, Georgia, United States, 3 Division of Cardiology, Emory School of Medicine, Atlanta, Georgia, United States
Show AbstractMany inflammatory diseases are progressive, with different treatments being needed during various phases of the disease. Microparticles have widely been used as drug delivery devices for the sustained delivery of numerous therapeutics. Work in our laboratory has shown that the polyketal microparticles, formulated from poly(cyclohexane-1,4-diyl acetone dimethylene ketal) (PCADK), exhibits excellent properties for sustained delivery of hydrophobic, anti-inflammatory drugs to a myocardial infarction animal model. Polyketals are ideal for treating inflammatory diseases due to their nontoxic and neutral degradation products. Hydrophilic therapeutics, such as proteins and RNAi, hold promise for treating diseases, however delivery through microparticle systems have been hindered due to low loading efficiencies and the large amount of material required for formulations. We hypothesized that by adapting immobilized metal affinity chromatography (IMAC) chemistry for drug delivery, we could efficiently load proteins in a quantitative manner to the surface of PCADK microparticles while maintaining sustained release of hydrophobic drugs from the bulk of the microparticle.We have fabricated PCADK microparticles bearing nitrilotriacetic acid (NTA) on the surface of the particle. NTA is routinely used to chelate nickel ions and purify recombinantly-expressed proteins with the His6-tag. We investigated the binding properties of the microparticles using His6-tagged green fluorescent protein (GFP). At 10% NTA, we found a maximum loading of 45 ng GFP per mg particle in a dilute solution (<1.5 μg/mL). This corresponded to a loading efficiency of 40%. Similar efficiencies were achieved using 1% NTA, though particles saturated at 30 ng GFP per mg particle. Binding was shown to be nickel-dependent and fully reversible with the addition of immidazole. In prior studies from our laboratory, the small molecule p38-inhibitor SB239063, had a release half-life of approximately one week from the bulk of the microparticle. In vitro studies using the NTA-Ni particles indicated that the release half-life of GFP was approximately 24h under physiological conditions (pH 7.4, 10% serum, 37°C). Ongoing work in our laboratory focuses on using the NTA-Ni microparticle chemistry to deliver growth factors as well as adding targeting ligands for cell surface receptors.Polyketal microparticles hold great promise for drug delivery applications. In this work, we investigated the use of IMAC strategies to reversibly bind His6-tagged proteins to the surface of microparticles. The ability to have quantitative dual release kinetics from a single microparticle could have an impact in treating progressive diseases by controlled delivery of different drugs at specific times. Since many commercially available proteins are recombinantly expressed with His6-tags, NTA-functionalized microspheres should prove to be a flexible platform for dual-mode delivery of bioactive compounds.
12:30 PM - HH2.5
Nanoparticles of Porous Iron Carboxylates as New Drug Carriers.
Patricia Horcajada 1 , Christian Serre 1 , Ruxandra Gref 2 , Tamim Chalati 2 , Gerard Ferey 1 , Patrick Couvreur 2
1 Institut Lavoisier, University of Versailles, Versailles France, 2 Faculty of Pharmacy, University Paris XI, Chatenay Malabry France
Show AbstractThe need of molecules of very high molecular weight and/or with a low aqueous solubility in chemotherapy makes indispensable the development of new drug carriers. Polymeric and mixed systems have been recently proposed for controlled release of drugs with higher efficiency(1). However, the actual delivery systems are not able to satisfy the necessary requirement for a large number of molecules of high therapeutic interest such as Busulfan (Bu; antitumoral agent)(2) and Azidothimidine triphosphate (AZT-TP; antiretroviral drug), which show important problems as a poor stability(3), toxicity effects(4) or a low bioavailability(5,6). A new alternative to encapsulate drugs, never tried before, is the use of nanoparticles of porous Metal-Organic-Frameworks (MOFs). These solids combine a high pore volume and a regular porosity, as well as the presence of organic groups easily tuneable within the framework(7). Thus, very high drug storage capacities, up to 1.4 g of Ibuprofen/g of MOF, with a complete drug controlled release under physiological conditions from 3 to 6 days were achieved using rigid MOFs(8). In addition, the use of the flexible porous MOFs led to an unsually long drug release(3 weeks) with a loading capacity of 20% (wt/wt).(9) Moreover, according to their composition, these materials possess a priori a low toxicity and a hydrophobic/hydrophilic internal microenvironment conveniently adapted to host a large number of different molecules(10). This work reports the use for the first time of nanoparticles of porous iron (III) carboxylates as new drug delivery systems(11). The encapsulation and release of different antitumoral and retroviral drugs into these porous hybrids solids were studied. Drug loadings 60 times more effective than in liposomes and 4 times more effective than the best systems polymer-based were achieved (up to 20 %wt) with a controlled release of the drug, which makes their use very promising for a better administration of cytotoxic drugs. In addition, the design of the porous hybrid solids, playing with the wide range of compositions and topologies, will allow adapting these porous hybrid matrices to the host molecule, according to its structure and its dosage requirements. 1. Freiberg S. et al. Internat. J. Pharmac. 2004, 282, 12. Nashyap A. et al. Biol. Blood Marrow Transplant., 2002, 8, 4933. Li X., Chan W. K., Advanced Drug Delivery Reviews 39,1999, 81 4. Baron F. et al. Haematologica 1997, 82, 7185. M. Kukhanova et al. Curr. Pharm. Des. 6, 2000, pp. 5856. Hillaireau H. et al. J. Controlled Release 116, 2006, 3467. Serre C. et al. Science, 2007, 315, 1828; Férey G. et al. Science, 2005, 309, 2040.8. Horcajada P. et al.Angew. Chem. Int. Ed., 2006, 45, 5974.9. Horcajada P. et al. J. Am. Chem. Soc.,2008, 130, 6774.10. Ghermani N.E. et al.Pharmac. Research, 2004, 21, 598.11. Horcajada P., Serre C., Gref R., Férey G., Couvreur P., FR 07/06873, 01 october 2007 and FR 07/06875, 01 october 2007
12:45 PM - HH2.6
Protein-Nanoparticle Conjugates As Neuroprotective Agents.
Vladimir Reukov 1 , Victor Maximov 1 , Alexey Vertegel 1
1 , Clemson University, Clemson, South Carolina, United States
Show AbstractNeurons continue to die for hours following traumatic spinal cord injury. Secondary injury is a combination of several factors contributing to cell death, including free radical damage and glutamatergic excitotoxicity. Here we study attachment of superoxide dismutase (SOD) and glutamate receptor antibody to poly(butylcyanoacrylate) (PBCA) nanoparticles with the ultimate goal to design biomedical nanodevices for treatment of secondary spinal cord injury. Ability to penetrate the blood-brain barrier (BBB) is a unique property of PBCA nanoparticles that can be used for drug delivery to the central nervous system (CNS). Synthesis of monodispersed 100 nm PBCA nanoparticles was performed using polymerization at pH 2.0 using Dextran-70 as the stabilizer. Sulfo-HSAB spacers were used to covalently attach superoxide dismutase and anti-NR1 glutamate receptor antibodies to the nanoparticles. Aggregation of protein-nanoparticle conjugates was not observed. Composition of the protein-nanoparticle conjugates can be controllably changed by varying protein concentrations in the initial mixtures. Activity of covalently attached SOD consisted of 70-80% of that of the free enzyme even after 3 week storage at 4°C. The observed high activity and storage stability are very important for future therapeutic applications. Strong binding of the protein-nanoparticle conjugates containing NR1 glutamate receptor antibody to rat dorsal ganglion neurons was observed. The effectiveness of such conjugates against generated superoxide was studied on primary rat neurons cell culture. About 200 uL of conjugate suspension was added to the well with neurons, and than xanthine(25uM) and xanthine oxidase(10 mU/mL) solution were added into the same well. Cell viability was determined using a fluorescent live / dead cell assay. We found that superoxide dismutase (SOD) and glutamate receptor antibody to poly(butylcyanoacrylate) (PBCA) nanoparticles shows high activity against generated superoxide radicals.This work was supported by South Carolina Spinal Cord Injury Research Fund grant # 0206.
HH3: Advanced Biomaterials II
Session Chairs
Monday PM, December 01, 2008
Room 310 (Hynes)
2:30 PM - HH3.1
Shape-memory Properties of Multiblock Copolymers Consisting of Poly(ω-pentadecalactone) Hard Segments and Crystallisable Poly(ε-caprolactone) Switching Segments.
Karl Kratz 1 2 , Ulrike Voigt 2 , Wolfgang Wagermaier 2 , Andreas Lendlein 1 2
1 , Center for Biomaterial Development and Berlin-Brandenburg Centre for Regenerative Therapies (BCRT), Teltow Germany, 2 , GKSS Forschungszentrum Geesthacht GmbH, Teltow Germany
Show Abstract2:45 PM - HH3.2
Magnetron-Sputtered Zinc Doped Hydroxyapatite Thin Films for Orthopedic Applications.
Patrick Marti 1 , Serena Best 1 , Zoe Barber 1 , Roger Brooks 2 , Neil Rushton 2
1 Department of Materials Science & Metallurgy, University of Cambridge, Cambridge United Kingdom, 2 Department of Surgery, University of Cambridge, Cambridge United Kingdom
Show AbstractThe coating of metallic bone and joint implants with hydroxyapatite (HA) has been shown to improve bone apposition and growth in vivo. Magnetron sputtering has attracted great interest due to its ability to produce dense, uniform thin coatings on metallic substrates. Furthermore, magnetron co-sputtering provides a straightforward method of incorporating elements into HA coatings, as has been done previously with silicon doped HA coatings, which out-performed regular HA coatings in vitro. Zinc is a trace element found in bone which has been shown to improve osteoblast proliferation and inhibit osteoclast growth in vitro. As a result, several investigations have produced and characterized zinc-substituted calcium phosphates with positive results. However, to date there have been no studies which have looked at the incorporation of zinc into HA coatings. The aim of this study was to produce and characterize zinc-doped HA thin films using rf-magnetron sputtering as a potential coating for metallic bone and joint replacement implants.For each sputtering run, radio-frequency power was supplied to a phase-pure sintered HA target at 60 W, and a direct current was applied to a zinc target at a power of either 1.5 W or 3.0 W. Ti-6Al-4V discs (10 mm diameter) were ground with 1200 grit SiC paper and cleaned prior to sputtering for 4 hours at a pressure of 0.8 Pa. Samples were heat-treated at 600 C for 3 hours in an Ar/Water atmosphere to ensure crystallization of the coatings.Uniform thin films of zinc-doped HA were produced with an approximate thickness of 600 nm. EDS was used to determine that the zinc content of the coatings produced with Zn target DC powers of 1.5 W and 3.0 W were 3.8 wt. % and 7.0 wt. % zinc, respectively. XRD revealed that the as-coated films were amorphous, and that heat treatment at 600 C resulted in the formation of a highly crystalline coating.Human osteoblast precursor cells were plated onto uncoated Ti-6Al-4V discs and Zn doped HA coated discs at a concentration of 10000 cells/disc. After 1, 4, and 7 days, cells were fixed with 4% paraformaldehyde, made permeable with Triton-X 100, and stained with Phalloidin TRFC and DAPI. Fluorescent microscopy showed significant attachment and growth of cells on each surface after 1 day. After 7 days, the 3.8 wt. % Zn doped HA coatings showed greater cell proliferation than both the Ti-6Al-4V and 7.0 wt. % Zn doped HA surfaces. This study demonstrates that a novel zinc doped HA coating produced using a magnetron co-sputtering process may have great promise for applications in the field of orthopedic biomaterials.
3:15 PM - HH3.4
Novel Biologically-inspired KRSR and RGD Modified Rosette Nanotube Coatings on Orthopedic Implants.
Lijie Zhang 1 , Usha Hemraz 2 , Hicham Fenniri 2 , Thomas Webster 1
1 Engineering, Brown University, Providence, Rhode Island, United States, 2 National Institute for Nanotechnology and Department of Chemistry, University of Alberta, Edmonton, Alberta, Canada
Show AbstractDue to the increasing number of patients who suffer various bone diseases and problems (such as implant loosening, etc.) related to conventional orthopedic implant materials (i.e., titanium), it is desirable to develop novel biomaterials which can significantly lengthen the service lifetime of orthopedic implants and, thus, dramatically reduce the relatively high percentage of orthopedic revision procedures performed around the world. The aim of this study was to create a novel biologically-inspired coating based on the self-assembly properties of helical rosette nanotubes (HRNs) with favorable cytocompatibility properties for improving orthopedic implants. HRNs are a series of biocompatible nanomaterials which spontaneously form in water or various solvents by the self-assembling of guanine-cytosine DNA motifs. Several types of novel HRNs with unique surface chemistry were synthesized and characterized in this study: HRN-K, HRN-RGD-K, HRN-KRSR, which were conjugated with respective cell-adhesive domains lysine (K), RGD, and KRSR peptide sequences. After coating these biomimetic HRNs on currently implanted titanium, the results of this study showed greatly improved osteoblast (bone-forming cell) adhesion after 4 hours compared to uncoated titanium. Additionally, HRNs performed much better towards improving bone cell adhesion than poly lysine, collagen, and KRSR peptides. Since other cells (such as endothelial cells for vascularization and fibroblasts for forming fibrous tissue capsule) also play important roles in new bone formation, the responses of vascular endothelial cells and skin fibroblasts towards these new KRSR and RGD modified HRN coatings were investigated. In total, this study created a novel nanostructured coating which can significantly improve bone cell adhesion and stimulate new bone growth, and thus, are worth further investigation.
3:30 PM - HH3.5
Activatable Nanoparticle-Tagged Perfluorocarbon Droplets for Medical Imaging.
Naomi Matsuura 1 , Ivan Gorelikov 1 , Ross Williams 1 , Kelvin Wan 1 , Siqi Zhu 1 , James Booth 2 , Peter Burns 1 , Kullervo Hynynen 1 , John Rowlands 1
1 Imaging Research, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada, 2 Molecular and Cellular Biology, Sunnybrook Health Sciences Centre, Toronto, Ontario, Canada
Show AbstractThere is interest in designing multifunctional constructs for clinical medical imaging that can both amplify weak native contrast at disease sites and be activated through means external to the patient to deliver localized therapy. Perfluorocarbon (PFC) droplets have been shown to be effective medical imaging contrast agents, and nanoparticles have been used as both imaging and therapy agents. In this work, the combination of PFC droplets and nanoparticles as hierarchical, composite constructs that may be activated by ultrasound energy was investigated for multifunctional imaging/therapy applications. Silica-coated, CdSe/ZnS, quantum dot (QD) nanoparticles were dispersed in PFC after surface fluorination, and were subsequently emulsified using synthetic fluorosurfactants to form sub-micron, QD-tagged PFC droplets in water. QD fluorescence and transmission electron microscopy were used to confirm that the QD-tagged PFC droplets successfully labeled live macrophage cells in vitro. To activate the QD-tagged PFC droplets, ultrasound pulses (peak negative pressures from 0 to 2 MPa) were applied to convert them to gas bubbles, which were rapidly driven to collapse. At ultrasound pressures greater than 1.6 MPa, the activation of the PFC droplets in the cells resulted in cell membrane disruption and dispersion of the cell contents into surrounding media. Activation of the PFC droplets was further validated by the decrease in total cell count of PFC-loaded cells after ultrasound exposure. This work reveals the potential of using ultrasound-activatable nanoparticle-PFC constructs to track transplanted ex vivo-labeled cells in vivo or to image acoustically the cellular target of similarly labeled constructs.
3:45 PM - HH3.6
Maghemite Nanoparticles Embedded in a Silica Shell as Enhanced T2 Contrast Agent for MRI.
Elena Taboada 1 , Anna Roig 1 , Elisenda Rodriguez 2
1 Crystallography Dpt., Institut de Ciència de Materials de Barcelona (ICMAB-CSIC), Bellaterra Spain, 2 Center for Molecular Imaging Research, MGH-Harvard Medical Hospital, Boston, Massachusetts, United States
Show Abstract4:00 PM - HH3: ADBIOMAT
BREAK
HH4: Drug Delivery Systems II Gene and Peptide Delivery
Session Chairs
Monday PM, December 01, 2008
Room 310 (Hynes)
4:30 PM - **HH4.1
A Multilayered Approach to Surface-Mediated DNA Delivery.
David Lynn 1
1 Department of Chemical and Biological Engineering, University of Wisconsin - Madison, Madison, Wisconsin, United States
Show AbstractMethods for the layer-by-layer deposition of oppositely charged polymers on surfaces can be used to fabricate ultrathin, multilayered films using a broad range of natural and synthetic materials, including DNA. Provided that the individual components of these assemblies are designed appropriately, these methods provide opportunities to design thin films and coatings that provide control over the release of proteins, DNA, and other agents from surfaces.We will describe recent work from our laboratory on the fabrication of ultrathin multilayered films that provide tunable and, in some cases, sophisticated levels of spatial and/or temporal control over the release of DNA from the surfaces of macroscopic and microscopic objects. Our work has centered on two primary approaches. The first approach is based on the fabrication of multilayered films using synthetic cationic polymers designed to degrade hydrolytically. The incorporation of degradable polyamines into these films introduces a mechanism for promoting controlled film disruption and the surface-mediated delivery of DNA. We have demonstrated that films fabricated using these materials erode gradually and can be used to direct surface-mediated cell transfection in vitro and in vivo. We have also demonstrated that changes in polymer structure can be used to provide tunable control over film disassembly. For example, systematic changes in polymer hydrophobicity, side chain structure, or charge density can be used to tune film erosion and the release of DNA over periods ranging from several hours, several days, or several weeks.The second approach is based upon the synthesis and incorporation of new synthetic ‘charge-shifting’ cationic polymers that undergo gradual reductions in net charge (e.g., from ‘cationic’ to ‘less cationic’ or ‘anionic’) and introduce time-dependent destabilizing interactions in DNA-containing films. We will discuss two different approaches to the design of these ‘charge-shifting’ polymers and examples of how these new polymers can be used to (i) design ultrathin films that promote the long-term release of DNA (e.g., for up to 3 months) and (ii) design multilayered films with hierarchical structures that permit control over the release of two or more DNA constructs with separate and distinct release profiles (e.g., rapid release of one DNA construct, followed by the slower, sustained release of a second DNA construct, etc).We will also describe the results of experiments demonstrating the abilty of these thin film coatings to localize the release of DNA from the surfaces of implantable medical devices, such as intravascular stents, or from the surfaces of injectable polymer microspheres. These new materials could contribute to the design of thin films and coatings capable of delivering precise and well-defined quantities of multiple different DNA constructs (or combinations of other agents) in a range of fundamental and applied contexts.
5:00 PM - HH4.2
DNA Delivery Using pH-Sensitive Polymer Vesicles.
Hannah Lomas 1 , Irene Canton 1 , Marzia Massignani 1 , Adam Blanazs 2 , Steven Armes 2 , Andrew Lewis 3 , Giuseppe Battaglia 1
1 Biomaterials and Tissue Engineering Group, Department of Engineering Materials, The Kroto Research Institute, The University of Sheffield, Sheffield United Kingdom, 2 Department of Chemistry, The University of Sheffield, Sheffield United Kingdom, 3 , Biocompatibles UK Ltd, Farnham Business Park, Farnham, Surrey United Kingdom
Show AbstractWe present a novel non-viral gene delivery vector based on the ability of a synthetic amphiphilic block copolymer to mimic biological phospholipids by forming membrane-enclosed structures, specifically nanometer-sized vesicles.1,2 We report the use of a diblock copolymer which comprises a biocompatible, hydrophilic polymer, poly(2-(methacryloyloxy)ethyl phosphorylcholine) (PMPC), and a pH-sensitive polymer, poly(2-(diisopropylamino)ethyl methacrylate) (PDPA), which can bind nucleic acids. The block copolymer self-assembles into vesicles at physiological pH, and dissolves completely as unimers at endocytic pH. Plasmid DNA has been successfully encapsulated inside these vesicles, and delivered intracellularly. We report that plasmid DNA-loaded PMPC25-PDPA70 polymer vesicles are able to transfect human primary cells (human dermal fibroblasts [HDF]) and an animal cell line (Chinese hamster ovary cells [CHO]) via the pH-triggered collapse of the vesicle.3 When the PDPA block of the PMPC-PDPA copolymer is protonated (at pH values below its pKa) it can also bind the highly negatively charged nucleic acids. We have characterized the DNA-copolymer interactions by ethidium bromide displacement assays, dynamic light scattering, transmission electron microscopy, and analysis of the zeta potential.3 All these techniques have confirmed that the self-assembly of the copolymer into vesicles at neutral pH is not affected by the presence of DNA and that the nucleic acid can be physically encapsulated within the polymer vesicle aqueous core, with a maximum encapsulation efficiency of 55 %. At acidic pH, the copolymer interacts strongly with DNA leading to the formation of a copolymer-DNA complex. Both GFP- and luciferase- encoding plasmid DNA have been encapsulated inside the polymer vesicles, and delivered into HDF and CHO cells.3,4 Compared to the use of more traditional non-viral vectors, such as LipofectamineTM and calcium phosphate, the PMPC-PDPA vesicles displayed very high levels of cellular viability, resulting in a much higher transfection efficiency. Furthermore, levels of protein expression when using these polymer vesicles to transfect cells were comparable to transfection using calcium phosphate.REFERENCES1. Discher, D. E. and Eisenberg, A. Polymer vesicles. Science, 297, 967-73, 2002.2. Battaglia, G. and Ryan, A. J. Bilayers and Interdigitation in Block Copolymer Vesicles. J. Am. Chem. Soc., 127, 8757-8764, 2005.3. Lomas, H. et al. Biomimetic pH Sensitive Polymersomes for Efficient DNA Encapsulation and Delivery. Advanced Materials, 19, 4238-4243, 2007. 4. Lomas, H., Massignani, M. et al. Non-cytotoxic polymer vesicles for rapid and efficient intracellular delivery. Faraday Discuss., 139, 2008 (in the press).
5:15 PM - HH4.3
Role of Shell Structure and Surface Chemistry in the Cytosolic Delivery of SiRNA, Proteins, and Viral Particles into Cells using Endosome-escaping Core-shell Nanoparticles.
Darrell Irvine 1 3 2 , Yuhua Hu 4 , Prabhani Atukorale 3 , Eun Chol Choi 1
1 Materials Sci. and Engineering, MIT, Cambridge, Massachusetts, United States, 3 Biological Engineering, MIT, Cambridge, Massachusetts, United States, 2 Koch Institute for Integrative Cancer Research, MIT, Cambridge, Massachusetts, United States, 4 Chemical Engineering, MIT, Cambridge, Massachusetts, United States
Show AbstractWe recently developed a strategy for achieving non-toxic endosomal escape of drug delivery nanoparticles by sequestering proton sponge polymers in the core of crosslinked polymer nanoparticles with a stable core-shell structure. These particles absorb protons near neutral pH, promoting osmotic swelling and rupture of endolysosomes following uptake by cells. In epithelial cells, fibroblasts, and dendritic cells (phagocytic cells of the immune system), core-shell particles were capable of transporting small molecule or protein cargos to the cytosol, including cargos as large as ~100 nm viral particles. Importantly, endosome disruption was readily achieved in > 95% of particle-loaded cells while maintaining cell viability > 90%, as assessed by measurements of cell metabolism or long-term cell growth assays. Changes in the charge and chemistry of the shell layer of the particles, incorporating nonionic hydrophilic moieties such as poly(ethylene glycol) or charged groups such as carboxylates or primary amines did not alter the endosome disruption capacity of the particles, thus enabling the surface properties to be tuned. Tailoring of the surface chemistry enabled facile, nontoxic delivery of small interfering RNA (siRNA) molecules for gene regulation in live cells.
5:30 PM - HH4.4
Polyelectrolyte Multilayer Drug Delivery of Antimicrobial Peptides.
Anita Shukla 1 , Robert Langer 1 , Paula Hammond 1
1 Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractMedical conditions are often exacerbated by the onset of infection caused by hospital dwelling bacteria such as Staphylococcus aureus. The overuse of antibiotics has led to a rise in antibiotic resistance of these bacteria. Novel therapeutics that effectively target a range of bacteria without contributing to a rise in antibiotic resistance are needed to tackle this problem. The effective delivery of antimicrobial peptides, an important component of the eukaryote innate immune system, is of interest due to their wide range of activity against gram positive and gram negative bacteria, as well as low onset of bacterial resistance. Our work focuses on using polyelectrolyte multilayer films (PEMs) for the delivery of these novel therapeutics targeting S. aureus infections. PEMs allow the incorporation of a broad spectrum of materials and highly tunable dosage. We have examined hydrolytically degradable layer-by-layer (LBL) constructed films for the delivery of an antimicrobial peptide, ponericin G1. This peptide exhibits a low S. aureus minimum inhibitory concentration, as well as low blood cell lysis. Poly(β-aminoesters), containing hydrolysable ester bonds, have been incorporated into PEMs in order to effectively deliver functional doses of ponericin G1 over the desired release time scales. Current results show this technique to be highly effective for ponericin delivery. Ponericin is released over several days, with a large initial release of drug from the film intended to immediately eliminate bacteria surrounding the film. This is followed by a more gradual release of ponericin to maintain a bacteria-free zone. The film released ponericin retains its activity against S. aureus. Various film architectures are being explored to achieve the most desirable release properties of ponericin G1, including co-release with basic fibroblast growth factor. Toxicity of released agents against NIH 3T3 Fibroblasts and Human Umbilical Vein Endothelial cells is also being studied.
5:45 PM - HH4.5
Nanostructured Ceramic Coatings for Drug Delivery.
Karin Dittmar 1 , Arnaud Tourvieille 1 2 , Laurent-Dominique Piveteau 2 , Heinrich Hofmann 1
1 Laboratory of Powder Technology, Ecole Polytechnique Fédérale de Lausanne, Lausanne Switzerland, 2 , Debiotech SA, Lausanne Switzerland
Show AbstractMedical implants delivering drugs are often used to ensure efficient medication at body sites where systemic administration is insufficient. The combination of a drug delivery coating on a mechanically supporting substrate is a beneficial concept for implants exposed to loads, e.g. stents or orthopaedic implants. Many of the commercially available coated stent implants are designed to release a drug locally and with a predefined rate out of a polymer matrix. These polymers are biodegradable, bio-erodible or inert. In spite of their successful drug release capability, they have often failed in regards to biocompatibility, long-term chemical and mechanical stability. This project aims at creating a novel, structured, ceramic drug delivering coating for stent implants. The coating is produced on a substrate by a multi-step dip coating technique into a TiO2-nanoparticle and a template suspension. Following sintering burns out the template particles to create a thin ceramic coating with defined meso and macro pores. The porosity of the mesoporous structure is greater than 50 %, as could be determined by nitrogen sorption and mercury intrusion porosimetry. This porosity can be increased if the macro pores (diameter 1 to 5 um, created by the templates) are present in the coating. The mean pore diameters of the mesoporous structure are 40 and 200 nm and the layer features a specific surface area below 20 m2/g. Anatase/rutile crystalline phases were determined in the ceramic by thin film XRD. The porosity of the film and the biocompatibility of TiO2 make the coating an ideal candidate as a drug reservoir and drug eluting system to be coated on stents.In drug eluting stents, immunosuppressive or anti proliferative agents are applied to prevent restenosis. In this study, paclitaxel is loaded into the coating by a low- pressure solvent evaporation technique. The amount of drug embedded and its release in different media are quantified by high performance liquid chromatography. The load obtained until now ranges from 0.2 up to 1.2 µg/mm2 (geometric area of the coating). Release tests in ultra pure water have revealed a continuous liberation of paclitaxel up to 2 month. Since a prolonged drug release is favourable to prevent restenosis on a long-term period, studies are now done to optimize the load and release kinetics of the drug. Results will be presented.First results of an in-vitro biocompatibility test using bovine endothelial cells in direct contact with the coated substrate showed a good biocompatibility of the coating. A major challenge lies in the compromise between a thin mechanically stable coating and the drug loading levels needed for the clinical application. The detailed characterization of the coating’s mechanical properties is therefore being conducted. Fracture starting point, delamination starting point and maximum shear strength between the coating and the substrate have been measured and will be presented.
HH5: Poster Session: Functional Materials and Drug Delivery Systems
Session Chairs
Tuesday AM, December 02, 2008
Exhibition Hall D (Hynes)
9:00 PM - HH5.1
Favorable Surface Adhesion Response of Electrodeposited Nano-hydroxyapatite on Ultrafine-grained (UFG)/nano-grained (NG) Austenitic Stainless Steel.
Sachin Mali 1 , Mahesh Somani 1 , L. Karjalainen 1 , Devesh Misra 1 , Sashank Nayak 1
1 Center for Structural and Functional Materials, University of Louisiana at Lafayette, Lafayette, Louisiana, United States
Show AbstractWe describe here the significance of ultrafine-grained (UFG)/nanograined (NG) structures in the electrodeposition of nano-hydroxyapatite and compare with conventional coarse-grained structures. The study demonstrates superior adhesion of electrodeposited nano-hydroxyapatite on UFG/NG structures in relation to coarse-grained austenitic stainless steel examined using nanosratching by a nanoindenter. It is proposed that hydrophilicity (contact angle) and grain structure are the underlying reasons for the difference in nanoscratching or adherent nature of nano-hydroxyapatite coatings on coarse-grained and UFG/NG austenitic stainless steel. An accompanying aspect that emerged from the primary objective is that the amorphous calcium phosphate is a precursor to the formation of nano-hydroxyapatite.
9:00 PM - HH5.10
Synthesis of Magnetic Porous Hollow Silica Nanostructures for Drug Delivery.
Hui Ma 1 , Mark DeCoster 2 , James McNamara 2 , Daniela Caruntu 1 , Jianfeng Chen 3 , Charles O'Connor 1 , Weilie Zhou 1
1 AMRI/Chemistry, Advanced Materials Research Institute/UNO, New Orleans, Louisiana, United States, 2 Biomedical Engineering and Institute for Micromanufacturing , Louisiana Tech University, Ruston, Louisiana, United States, 3 Key Lab for Nanomaterials, Ministry of Educations,, Beijing University of Chemical Technology, Beijing China
Show AbstractMagnetic porous hollow silica nanostructures with advantages of high surface area, good bio-compatibility and magnetic targeting, are considered as novel drug carriers in nanomedcine applications. In this presentation, we report a synthesis of magnetic porous hollow silica nanospheres and nanotubes using sol-gel method. Pure CaCO3 nanoneedles were first fabricated in rotating packed bag (RPB). Then Fe3O4 nanoparticles (diameter less than 10 nm)/methanol dispersion was added to attach the CaCO3 nanoparticles and nanoneedles surface. Surfactant hexadecyltrimethylammonium bromide (CTAB) was used as a template to direct the formation of porous structure on the surface. Tetraethoxysilane (TEOS) was then applied to generate silica by basic hydrolysis. After removing CTAB by calcination and etching CaCO3 nanoparticels and nanoneedles away in diluted acetic acid, magnetic porous hollow silica nanospheres and nanotubes with Fe3O4 nanoparticles embedded in the silica shell are achieved. The mangnetic porous hollow silica nanostructures were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and x-ray powder diffraction. SQUID measurement shows the nanostructures exhibit superparamagnetism property in room temperature, and ferromagnetism below the blocking temperatures. The drug loading/releasing tests using ibuprofen were studied and a slow release was observed. The toxicity test was also performed.
9:00 PM - HH5.11
Novel Superparamagnetic Iron Oxide Nanoparticles for a Multifunctional Nanomedicine Platform.
Oleh Taratula 1 3 , Ronak Savla 1 3 , Ipsit Pandya 1 , Andrew Wang 2 , Tamara Minko 3 4 , Huixin He 1 4
1 Chemistry, Rutgers, the State University of New Jersey, Newark, New Jersey, United States, 3 Department of Pharmaceutics, Ernest Mario School of Pharmacy, Rutgers, the State University of New Jersey, Piscataway, New Jersey, United States, 2 , Ocean NanoTech, Fayetteville, Arizona, United States, 4 , Cancer Institute of New Jersey, New Brunswick, New Jersey, United States
Show Abstract9:00 PM - HH5.12
Single File Diffusion of Protein Drugs through Cylindrical Nanochannel.
Seung Yun Yang 1 , Jeong-A Yang 2 , Sei Kwang Hahn 2 , Jin Kon Kim 1
1 Environmental Science & Engineering and Chemical Engineering, POSTECH, Pohang Korea (the Republic of), 2 Material Science & Engineering, POSTECH, Pohang Korea (the Republic of)
Show AbstractDevelopment of drug delivery with the controlled and long-term release has been considered as one of the most promising biomedical applications. A wide range of materials and devices developed based on osmotically controlled diffusion and swelling-controlled delivery have been reported. Although the existing methods showed long-term stability and constant release, several adverse problems, such as burst of a drug, might be anticipated under some chemical environments. Here, we achieve the single file diffusion of protein drugs by using the nanoporous membrane with cylindrical nanochannels. Nanoporous membrane consists of separation layer prepared by polystyrene-block-poly(methyl methacrylate) copolymer and conventional microfiltration membrane for the supporting membrane. We found that the rate of protein drug release throughout the nanoporous membrane becomes constant irrespective of the concentration of the drug. Since the pore size in the nanoporous membrane is easily controlled to match the size of drugs, it could be widely used for drug delivery of various proteins.
9:00 PM - HH5.13
Bioinspired Design of Polymer Films for Controlled Release of Self-assembling Colloidal Aggregate Containing Sirolimus.
Hyung Il Kim 1 4 , Madoka Takai 2 4 , Tomohiro Konno 2 4 , Ryosuke Matsuno 2 4 , Jeong-Sun Seo 3 , Kazuhiko Ishihara 1 2 4
1 Department of Bioengineering, School of Engineering, The University of Tokyo, Tokyo Japan, 4 Center for NanoBio Integration (CNBI), The University of Tokyo, Tokyo Japan, 2 Department of Materials Engineering, School of Engineering, The University of Tokyo, Tokyo Japan, 3 Ilchun Genomic Medicine Institute, MRC and Department of Biochemistry and Molecular Biology, Seoul National University College of Medicine, Seoul Korea (the Republic of)
Show AbstractExtensive clinical studies have reported better outcomes with sirolimus-eluting stents (SES) than with paclitaxel-eluting stents.[1] However, there are few published reports on the in vitro studies of sirolimus release in spite of poor control over the release from the current SES. The discrepancy between the clinical need and the poorly published in vitro data is probably due to instability of sirolimus in buffer. An attractive approach to stabilize bioactive agents is to develop a self-assembling colloidal aggregate of amphiphilic molecules. It was widely believed that only block copolymers could form reasonably controlled micelles before French and Canadian group published several reports about the colloidal stability of the integral membrane proteins/ amphiphilic random copolymers complex in buffer; the size dispersity was well controlled.[2] Earlier than their contribution to the field of polymer therapeutics, we originally reported that PMB30W, a water-soluble amphiphilic poly(2-methacryloyloxyethyl phosphorylcholine-random-n-butyl methacrylate), self-assembled into reasonably controlled colloidal aggregate and maintained hydrophobic drugs inside the micelles stably.[3,4] In this study, we hypothesized that PMB30W protect hydrolysis of sirolimus because the hydrophobic groups of PMB30W interact with the hydrophobic surface of sirolimus while phosphorylcholine groups of PMB30W provide a hydrophilic corona and thereby maintain the colloidal stability in aqueous medium. For the controlled release of sirolimus with good efficiency of drug loading, the novel domain-controlled release from poly(L-lactide-random-caprolactone-random-glycolide) (PLCG)/ PMB30W/ sirolimus films was designed. We controlled the release of sirolimus in vitro two compartment systems by tuning the size (by nano-range) of domains composed of PMB30W and sirolimus inside the PLCG/ PMB30W/ sirolimus blends. Three different formulations of films were designed; fast release (FR), moderate release (MR), slow release (SR) prepared by acetone/EtOH, acetone/MeOH, electrospinning in acetone/MeOH, respectively. The blend composition was fixed by 90/10/1 (PLCG/ PMB30W/ sirolimus, weight ratio). The size of domains composed of PMB30W and sirolimus was the main factor for determining the release velocity of sirolimus from the PLCG/ PMB30W/ sirolimus films; the release of sirolimus decreased while the size of the domains reduced. Electrospun nanofibers showed the remarkable structural stability in PBS and thereby became SR. Sirolimus was released by diffusion controlled manners; a degradation product of sirolimus released by degradation controlled. Compared to PLCG/ sirolimus films, all PLCG/ PMB30W/ sirolimus films reduced a degradation product of sirolimus significantly.References1. Serruys PW et al. N Engl J Med 354, 483, 2006.2. Diab C et al. Biochim Biophys Acta 1768, 2737, 2007. 3. Ishihara K et al. Polym J 31, 1231, 1999.4. Konno T et al. J Biomed Mater Res A 65, 210, 2003.
9:00 PM - HH5.14
Effect of Polymer Adsorption on Crystallization of Small Organic Molecules.
Hyemin Choi 1 , Jonghwi Lee 1
1 Department of Chemical Engineering and Materials Science, Chung-Ang University, Seoul Korea (the Republic of)
Show AbstractThe crystallization process of drugs is an important unit operation in the pharmaceutical industry. The controlled preparation of crystallites of a defined size can determine the kinetic aspects of solubility (drug release), crystal superstructures, and mechanical/flow properties. As the nucleation and growth processes in the crystallization of low molecular weight organic materials are sensitive to various parameters, crystallization can be controlled by addition of cosolvents, low molecular additives, heterogeneous surfaces, and sometimes functional polymers. Crystalline structures are often constructed by assembly and/or transformation from smaller units. It has been found that the morphology of polar organic crystals could be changed by the addition of oppositely charged polymeric additives, which can physically adsorb onto the surface of the smaller crystal units. To understand the role of polymer adsorption, the crystallization of atorvastatin calcium (a cholesterol-lowering statin drug) was performed in methanol/water (1:9(v/v)) mixture using 96-well plates. Polyethyleneimine(PEI), chitosan, bio-synthesized elastin like polymers [(GVGVP GVGVP GEGVP GVGVP GVGVP GVGVP)35(GVGVP) (PVII), and (GVGVP GVGFP GEGFP GVGVP GVGFP GFGFP)35(GVGVP) (PXIII)], poly(acrylic) acid(PAA) and polyethylene glycol(PEG) were used as polymeric additives. Crystal structure and particle morphology were analyzed by SEM, DSC and XRD. It is well known that many polymers in solution can induce colloidal aggregation by enthalpic changes (surface binding and interparticle bridging) as well as nonadsorption entropic mechanisms (depletion flocculation). This process is the molecular basis for polymer-directed crystallization. In addition, strong attractive interactions can prevent further crystal growth and change the shape and size of primary clusters. SEM showed distinctly different particle morphology in the cases of elastin like polymers: Overall, spherical particles were observed, but they consisted of smaller primary crystallites. Crystallization temperature also affected the size of crystals: The higher the temperature, the larger the crystal size resulted. Differences in particle sizes and pathway of crystal growth were obtained by using different kinds of polymers. There were significant differences in DSC melting points. This polymer-directed crystallization resulted in the formation of mesocrystals, artificially stabilized by polymeric additives. Interesting morphological features were observed in the mesocrystal cases. (G=glycine, V=valine, P=proline, I=isoleucine, F= phenyalanine and E=glutamic acid).
9:00 PM - HH5.15
Formulation Of A Hierarchically Designed Peptide Nucleic Acid Based DNA Delivery Construct.
Peter Millili 1 , Daniel Yin 3 , Haihong Fan 3 , Ulhas Naik 2 , Millicent Sullivan 3
1 Chemical Engineering, University of Delaware, Newark, Delaware, United States, 3 Pharmaceutical Sciences, Merck & Co., West Point, Pennsylvania, United States, 2 Biological Sciences, University of Delaware, Newark, Delaware, United States
Show Abstract9:00 PM - HH5.16
IR Spectroscopy and DSC Studies of Binary Combinations of cis-6-Octadecenoic Acid and Octadecanoic Acid – Relevance to Stratum Corneum Permeation.
David Moore 3 , Eilidh Bedford 1 2 , Donald Koelmel 3 , Donna Laura 3
3 , ISP, Wayne, New Jersey, United States, 1 Performance Products, Cabot Corporation, Billerica, Massachusetts, United States, 2 , Unilever, Port Sunlight United Kingdom
Show AbstractFourier transform infrared (FTIR) spectroscopy and differential scanning calorimetry (DSC) studies are reported for combinations of cis-6-octadecenoic acid (also termed petroselinic acid, PSA) and octadecanoic acid (also termed stearic acid, SA) across a wide range of binary mole ratio combinations. The data are then used to plot the phase diagram which is found to be montotectic with the PSA reducing the melting temperature of SA at all compositions. The relevance of these experiments to stratum corneum (SC) biophysical behavior, particularly the influence and potential mechanisms of PSA on dermal permeation, are discussed. The phase behavior of this simple binary model system indicates a potential mechanism by which cis-6-octadecenoic acid can act as penetration enhancer in skin, given that discrete fatty acid domains may exist in the SC. This lipid model suggests that cis-6-octadecenoic acid forms a fluid lipid phase in the SC (at skin physiological temperatures ~32-34 °C) that will include some amount of fluidized SC fatty acids. Cis-6-octadecenoic acid clearly disrupts the crystalline orthorhombic domains of octadecanoic acid resulting in smaller domains and a reduced melting temperature. This separate cis-6-octadecenoic acid-stratum corneum fatty acid fluid phase could provide a pathway in the SC through which lipophilic molecules permeate the skin barrier.
9:00 PM - HH5.17
Antisense Oligonucleotides Delivery to the Antigen Presenting Cells by using Schizophyllan.
Shinichi Mochizuki 1 , Jusaku Minari 1 , Mika Kasuga 1 , Yoshiyuki Adachi 2 , Kazuo Sakurai 1
1 , The University of Kitakyushu, Fukuoka Japan, 2 , Tokyo University of Pharmacy and Life Science, Hachioji, Tokyo Japan
Show AbstractAntisense oligonucleotides (AS ODNs) have a great advantage as therapeutic agents. AS ODNs are designed to bind to RNA through the Watson-Crick hybridization. In general, their size ranges from 12 to 25 nucleotides in length and their gene silencing mechanism includes cleavage of the targeted RNA with endogenous cellular nuclease, such as RNase H. Several phosphorothioate ODNs are in the late phase clinical trials as the first generation in antisense regent. However, in vivo, there are a number of obstacles to overcome, such as rapid excretion via kidney, degradation in serum, uptake by phagocytes of the reticuloendothelial system, and inefficient endocytosis by target cells. A variety of supramolecular nanocarriers including liposomes, cationic polymer complexes, and various polymeric nanoparticles have been used to deliver AS ODNs. We have studied schizophyllan (SPG) as an AS ODNs carrier. SPG, an extracellular polysaccharide produced by the fungus, is consists of β-(1→3) –D-glucan and one β-(1→6)-D-glycosyl side chain that links to the main chain at every three glucose residues. We have revealed that SPG can form a complex with polynucleotides. In 2001, Gordon et al. identified dectin-1 as a major receptor involved in the recognition of β-glucans. Dectin-1 is predominantly expressed on antigen presenting cells such as macrophages and dendritic cells. Therefore it is thought that AS ODNs complexed with SPG are specifically incorporated into the antigen presenting cells. We prepared HEK293 cells transfected with mouse dectin-1 cDNA in order to examine its ability to uptake of SPG. The extent of expression of dectin-1 was confirmed by RT-PCR and flow cytometry. To test whether the dectin-1 transfectant could uptake SPG, the dectin-1 transfectant was incubated with various concentration of fluorescein-labeled SPG, and the uptake was analyzed by flow cytometry. The dectin-1 transfectant showed the increased fluorescent intensity with a higher concentration of fluorescein-labeled SPG. However control HEK293 cells did not show the increased uptake of fluorescein-labeled SPG. This suggests that fluorescein-labeled SPG was specifically recognized by dectin-1 on the transfectant. The formation of complex between SPG and AS ODNs having poly (dA)30 was carried out with the established method and the complexation was confirmed by gel electrophoresis. After gel electrophoresis, AS ODNs reacted with SPG did not migrate at all, which indicated that AS ODNs were formed a complex with SPG. These data suggest that SPG is a useful biomaterial for delivering AS ODNs to the antigen presenting cells.
9:00 PM - HH5.18
Design, Synthesis, and Biological Functionality of a Modular Drug Delivery Platform.
Douglas Mullen 1 3 , Daniel McNerny 2 3 , Xue-min Cheng 3 , Alina Kotlyar 3 , Ankur Desai 3 , Istvan Majoros 3 , James Baker 3 , Mark Banaszak Holl 1 3 4
1 Macromolecular Science and Engineering Program, University of Michigan, Ann Arbor, Michigan, United States, 3 Michigan Nanotechnology Institute for Medicine and Biological Sciences, University of Michigan, Ann Arbor, Michigan, United States, 2 Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan, United States, 4 Department of Chemistry, University of Michigan, Ann Arbor, Michigan, United States
Show AbstractPoly(amidoamine) (PAMAM) dendrimers have shown great promise as targeted drug delivery platforms. Studies have demonstrated that PAMAM dendrimers functionalized with targeting moieties, drug molecules, and imaging dyes efficiently induce cytotoxicity in cancer cells without causing collateral damage to healthy cells. There remain several obstacles preventing large scale utilization of multi-functionalized dendrimers including multiple time-intensive synthesis steps, decreased solubility, and an increased PDI of the final product. Thus, a new approach to synthesize a modular drug delivery platform using mono-functionalized dendrimers is being pursued. This approach utilizes the specificity of the 1,3 dipolar cycloaddition reaction between azide and alkyne moieties to create multi-functionalized dendrimer platforms that have the same clinical properties as single multi-functional dendrimers while requiring fewer synthesis steps, achieving an increased carrying capacity, and minimizing PDI. Additionally, this approach has the added capability of creating different drug-target combinations in one combinatorial step, rather than requiring the complete synthesis for each desired combination.
9:00 PM - HH5.19
Layer-by-Layer Assembly of Block Copolymer Micelles for Applications in Drug Delivery from Surfaces.
Byeong-Su Kim 1 , Paula Hammond 1
1 Chemical Engineering, MIT, Cambridge, Massachusetts, United States
Show AbstractLayer-by-layer (LbL) assembly has been widely used as a versatile method for fabricating multilayer thin films with controlled structure and composition. Due to its facile, inexpensive, and environmentally friendly nature, LbL assembled multilayer thin films find their applications ranging from materials to biology. LbL assembly is typically based on sequential adsorption of materials with complementary functional groups employing electrostatic interaction, hydrogen bond, and coordination bond, which limits the incorporation of small, hydrophobic drugs into multilayer film. There is, therefore, widespread interest in finding ways to integrate therapeutic reagent into LbL film.Here, we describe the incorporation of amphiphilic block copolymer micelle as a nanometer-sized vehicle for hydrophobic drugs within the LbL multilayer films. In particular, we chose block copolymers containing biodegradable poly(ε-caprolactone) as a core block for controlled release, including poly(ethylene oxide)-block-poly(ε-caprolactone) (PEO-b-PCL), and poly(2-vinyl-N-ethylpyridinium bromide)-block-poly(ε-caprolactone) (P2VEP-b-PCL). We demonstrate the construction of polymer micelle containing films through different assembly condition employing either hydrogen-bonding for PEO-b-PCL micelle, or electrostatic interaction for P2VEP-b-PCL micelle. With these integrated nanostructures within LbL multilayer film, we have explored their potential uses as a platform for model drug incorporation and release under physiological condition.
9:00 PM - HH5.2
In-vitro Bioactivity and Mechanical Properties of a Novel Implantable Biomaterial: Nano-tricalcium Phosphate-silicone Rubber Nanostructured Composite.
Jinesh Shah 1 , Wah Wah Thein-Han 1 , Qiang Yuan 1 , Devesh Misra 1
1 Center for Structural and Functional Materials, University of Louisiana at Lafayette, Lafayette, Louisiana, United States
Show AbstractAn excellent vehicle to achieve the objective of good cell attachment and proliferation of fibroblast and osteoblast in conjunction with the desired mechanical properties in an implant is to consider compounding a bioactive material with the superior mechanical properties of a scaffold. The approach to accomplish this objective involves the synthesis of tricalcium phosphate (TCP) nanoparticles using the concept of reverse micelle, which are dispersed via shear mixing and ultra-sonication, followed by cryo-compounding with silicone rubber (SR) and pressure-induced solidification. Experiments using the approach have confirmed that high strength-at-break and undiminished intrinsic ductility of silicone rubber and high cytocompatibility are achieved by uniquely combining the high-extensibility of silicone rubber with bioactive and bone-bonding properties of nano-TCP. Such composites represent a new class of biomaterials for biomedical implants and scaffolds, where ultra-fine surface features are used to modulate cell-substrate interactions and to ensure the long term stability of the implant.
9:00 PM - HH5.20
Self-Assembly of Genetically Engineered M13 Bacteriophage and Functional Polymers into Macroscopic Vesicular Membranes and Fibers.
Woo-Jae Chung 1 2 , Seung-Wuk Lee 1 2
1 Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 2 Bioengineering, UC Berkeley, Berkeley, California, United States
Show AbstractWe report here on the use of engineered M13 bacteriophages as building blocks for the construction of novel biomaterials, which may have potential diverse application. The self-assembly of macroscopic vesicular membranes and fibers was induced by extrusion of M13 phage aliquots in aqueous solution containing cationic polymer which is able to interact with the negatively charged viruses at the interface.The M13 viruses for the self assembly have been genetically engineered to express functional peptides on 2,700 copies of its major coat proteins to impart the high density of functional motifs to the self-assembled structure. The fact that resulting structures were compatible under the physiological condition in prolonged time led us to investigate and demonstrate the in vitro studies of the protein (drug) release kinetics of the different types of the vesicular membranes and fibers.We additionally investigated the feasibility of employing the viral composite structures for the tissue engineering templates by monitoring the cell growth on an assembled viral surface displaying peptides that promote cell interaction (RGD, IKVAV).
9:00 PM - HH5.21
Synthesis and Characterization of Silica Particles as a Drug Delivery Vessel.
Sami Chanaa 1 , Hangning Chen 1 3 , Ben Estes 1 , John Larese 1 2
1 Chemistry, University of Tennessee, Knoxville, Tennessee, United States, 3 College of Chemistry and Chemical Engineering, Lanzhou University, Lanzhou, Gansu, China, 2 College of Chemistry and Chemical Engineering, ORNL, Oak Ridge, Tennessee, United States
Show Abstract9:00 PM - HH5.22
Structural Changes of Horse Cytochrome c in a Biomimetic System: AOT Reverse Micelles. A Molecular Modeling Study.
Stephane Abel 1 , Marcel Waks 2 , Msssimo Marchi 1
1 DSV/IBiTec-C/SB2SM, Commissairiat a l'energie atomique, Saclay France, 2 Laboratoire Imagerie Paramétrique, CNRS, LIP, UMR 7623, Université Pierre et Marie Curie Paris 6, Paris France
Show AbstractCytochrome c (CYTC) is a small (104 residues), basic (pHi=10.5), soluble hemoprotein, associated with the inner membrane of the mitochondrion. It plays an essential role in electron transfer (ET) at the level of the respiratory chain and in other cellular mechanisms such as apoptosis. CYTC interactions with surfactants have been extensively investigated as a model for electrostatic interactions of peripheral proteins with membranes. Physiological aspects of ET in various membrane biomimetic systems such as reverse micelles (RM) have been explored and mostly performed in RM of sodium bis-(2-ethylhexyl) sulfosuccinate (AOT) in isooctane. Since the size and the water amount in RM can be experimentally controlled by the following parameter: Wo=[H2O]/[AOT], i.e. the water-to-surfactant molar ratio, it provides a simple biomimetic system for the study of peptides and proteins in a membrane environment at various hydration levels. In AOT RM, it was shown that CYTC is located between the interface and the positively charged residues of the protein near the AOT headgroups. The electrostatic interactions therefore disrupt the protein secondary structure and affect the local heme environment. In particular, it was shown by fluorescence spectroscopy that in small RM (i.e. Wo < 20), the Met80(S)-Fe and His18(N)-Fe bonds are disrupted by the heme crevice opening. To examine at the atomic level these phenomena, we have used Molecular Dynamics Simulations (MD) at ambient conditions (P = 0.1 MPa and T = 300 K) using a previous atomistic model of AOT RM in isooctane (Abel, Waks, Urbach and Marchi, J. Am. Chem. Soc. (2006) 128, 382). Two RM sizes with Wo = [H2O]/[AOT] = 5.5 and 9.1 were constructed using large isooctane amounts (> 80 % w/w) to simulate an experimental L2 phase. We have compared the CYTC secondary structure and the heme environment changes as a function of water content to those of the protein in bulk water. Our results show that the protein secondary structure and heme conformational changes depend essentially on the micellar hydration. When the size of the water pool is close to the protein size and the micelle poorly hydrated, the protein structure and the heme moiety are both stable. With the increase of the water content, the protein structure becomes unstable due to the large displacement of the Met80 and the His18 residues from the iron when the heme crevice opens. Nevertheless, we observe that the secondary structure is not altered, in contrast to the heme structure. This fact suggests that the heme environment change is decoupled from that of the protein secondary structure, and probably due to the electrostatic field of the heme crevice positive charges. We conclude that structural alterations observed at the heme level are thus more sensitive to hydration than those occurring at the protein structure level itself.
9:00 PM - HH5.23
A Diagnostic Sensor using a Carbon Nanotube-polymer Composite for the Determination of Acetone in Aqueous and Urine Samples.
Gina Lein 2 , Kalathur Santhanam 1 2 , Lynn Fuller 3
2 Department of Chemistry, Rochester Institute of Technology, Rochester, New York, United States, 1 Center For Materials Science and Engineering, Rochester Institute of Technology, Rochester, New York, United States, 3 Microelectronics Engineering, Rochester Institute of Technology, Rochester, New York, United States
Show AbstractAn acetone sensitive composite has been synthesized using multiwalled carbon nanotubes (diameter 60-100 nm) and a choro-polymer. The sensor is constructed by depositing this composite onto a silicon wafer chip (1 mm length) having two gold electrodes separated by a tenth of a millimeter (1). The sensor resistance in distilled water was measured before and after injection of acetone into the medium. The resistance change is linear with concentration of acetone. The microsensor response to acetone in urine was evaluated by successive injections of acetone into the urine sample. The response, recovery times and sensitivity of the microsensor have been evaluated. Based on the response and the amount of acetone present- low, moderate and acute regions were defined to mark metabolic abnormalities of a person. Currently such abnormalities are characterized colorimetrically by Bayer strips. Although these strips are called acetone strips, they are designed to respond to acetoacetic acid with practically no response to acetone. Bayer strips are successful in the determination of a metabolic abnormality as both acetone and acetoacetic acid are the simultaneous degradation products of the metabolism. The performance of microsensor constructed here was compared with the Bayer strips that are available in the market; the strips do not respond to acetone (respond to acetoacetic acid) putting the microsensor at an advantageous position for the determination of acetone. The mechanism by which the microsensor responds to the acetone, has been examined and it appears that the original pyramidilization angle and misalignment of pi orbital that is present in the carbon nanotubes, changes upon adsorption of acetone on the active sites causing it to go from more metallic (conducting) to a less metallic (conducting) state. Upon desorption the original pyramidilization angle is restored, thus enabling the microsensor to be re-useable. Thus the microsensor could be successfully used for diabetic acetone.We acknowledge with thanks the complimentary strips provided by the Bayer Company------------------------------------------------------------------------------------------------------------1. K.S.V. Santhanam, R. Sangoi, L. Fuller, A chemical sensor for chloromethanes using a nanocomposite of multiwalled carbon nanotubes with poly(3-methylthiophene). Sensors and Actuators, B: Chemical (2005), B106(2), 766-771.
9:00 PM - HH5.24
Biodegradable Microfluidic Scaffolds for Tissue Engineering from Amino Alcohol-based Poly(ester amide) Elastomers.
Jane Wang 1 2 3 , Christopher Bettinger 1 2 , Robert Langer 3 4 5 , Jeffrey Borenstein 2
1 Material Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Biomedical Engineering Center, Charles Stark Draper Laboratory, Cambridge, Massachusetts, United States, 3 Program of Polymer Science and Technology, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 4 Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 5 Division of Health Sciences and Technology, Harvard-M.I.T., Cambridge, Massachusetts, United States
Show AbstractBiodegradable polymers with high mechanical strength, flexibility and optical transparency, optimal degradation properties and biocompatibility are critical to the success of tissue engineered devices and drug delivery systems. In this work, novel fully biodegradable scaffolds comprising microfluidic channels are fabricated with biodegradable elastomers for tissue engineering applications. Most biodegradable polymers suffer from short half life resulting from rapid degradation upon implantation, exceedingly high stiffness, and limited chemical moieties. Here we report a new biodegradable elastomeric poly(ester amide)s, poly(1,3-diamino-2-hydroxypropane-co-polyol sebacate)s (APS), which is synthesized and used rather than the traditional crosslinked aliphatic polyesters to address the abovementioned drawbacks. The microfludic scaffolds in this work showed a much lower Young’s Modulus and a much longer in vivo degradation half-life. The device is molded in a similar approach to that reported previously for poly-lactic-co-glycolic acid (PLGA) microfluidic channels, where the bonded microfluidic channels are shown capable of supporting moderate flow pressure. The fluid dynamics are also tested by developing microfluidic networks for cell culture and implantation. The device described here is high resolution and fully biodegradable; the fabrication process is fast, inexpensive, reproducible, and scalable, making the approach ideal for both rapid prototyping and manufacturing of tissue engineering scaffolds for liver and vasculature.
9:00 PM - HH5.26
Synthesis, Characterization and Preliminary Testing of Mesoporous Silica Nanoparticles for Drug Delivery Application.
Elayaraja Muthuswamy 1 , Shantaraj Bhattarai 2 , David Oupicky 2 , Stephanie Brock 1 , Michal Brichacek 1
1 Chemistry, Wayne State University, Detroit, Michigan, United States, 2 Pharmaceutical Sciences, Wayne State University, Detroit, Michigan, United States
Show Abstract9:00 PM - HH5.27
Covalent Tethering of Plasmid DNA for Substrate-Mediated Gene Delivery.
Kory Blocker 1 , Kristi Kiick 2 , Millicent Sullivan 1
1 Chemical Engineering, University of Delaware, Newark, Delaware, United States, 2 Materials Science and Engineering, University of Delaware, Newark, Delaware, United States
Show Abstract9:00 PM - HH5.29
Solid Lipid Templating of Open-pore Microscaffolds.
Kristina Ambrosch 1 , Michaela Schulz-Siegmund 1 , Michael Hacker 1
1 Pharmaceutical Technology, University of Leipzig, Leipzig Germany
Show AbstractMicroscaffolds, particulate macroporous polymer matrices with diameters below 1 mm, have become interesting matrices for tissue engineering applications that involve the in vitro culture of adherent cells as the dimensions of such constructs can be controlled in a way that cells within the scaffold may be sufficiently supplied with nutrients and oxygen from the surrounding media by passive diffusion. Compared to hydrogels, microscaffolds provide a mechanically stronger environment for cells to attach to. Besides the prospect of improved properties for effective suspension culture and cell differentiation in vitro, microscaffolds can be transplanted using minimally invasive techniques. It is envisioned that mature tissue fragments engineered on microscaffolds can eventually be assembled to larger and/or more complex tissues in vivo. Towards this end, microscaffolds of controlled volumes and porosities are required. Conventional double emulsion and/or gas foaming techniques often result in microbeads with controlled volumes but limited pore size and surface porosity.This work is concerned with the fabrication of poly(lactide-co-glycolide) (PLGA) microscaffolds with an open and interconnected network of pores with diameters around 50 μm through the use of solid lipid microspheres as porogen. Based on our experience with the solid lipid templating (SLT) technique for the fabrication of conventional scaffolds, we are exploring adaptations of this process to yield microscaffolds of the desired pore structure. Such advancements include the combination of SLT principles with processes that yield small individual particles or spheres, such as air atomization. In this approach, solid lipid particles (50 – 100 μm in diameter) were dispersed in a PLGA solution and the highly viscous dispersion was disrupted in small fragments by compressed air using a custom-made nozzle and collected in a non-solvent for the polymer. Subsequent to polymer solvent extraction the lipid porogen was extracted in n-hexane and the resulting porous particles were isolated and dried. Particle size was assessed microscopically and quantified by image analysis. Microstructure was examined by scanning electron microscopy. The effects of processing conditions on microscaffold size distribution and pore structure were determined and processing parameters were identified to fabricate microscaffolds of promising size and microstructure.
9:00 PM - HH5.3
Peptide-based Polyurethane Elastomers as Tissue Engineering Scaffolds
Elizabeth Cosgriff-Hernandez 1 , Thomas Wilems 1 , Nick Sears 1
1 Biomedical Engineering, Texas A&M University, College Station, Texas, United States
Show AbstractMusculoskeletal diseases and injuries have an enormous impact on quality of life and remain one of the leading reasons that patients seek medical care. Engineered tissue grafts have the potential to repair damaged ligaments when traditional transplants are unavailable or fail. We have developed a series of novel protease-sensitive polyurethanes as tissue engineering scaffolds that combine the strength and tunability of polyurethane elastomers with the cell-responsive degradation of collagen.Experimental: Peptide-based polyurethane elastomers were generated through a multistep process in which each of the building blocks was individually synthesized and verified prior to generation of the full polymer. This strategy provides direct control over the segmental chemistry of the polyurethane and provides exceptional tunability of the resulting structure and properties.Amine-Functionalized PEG: Dicyclohexylcarbodiimide (DCC) was added to amine-protected glycine (Fmoc Gly COOH) to activate the carboxyl group for subsequent reaction with PEG (MW = 2000 g/mol). Anhydrous pyridine was then added to initiate the formation of an ester link between the PEG chain and the activated C terminus of the glycine. The polymer was precipitated in diethyl ether, filtered, washed, and dried in vacuo. The polymer was again purified following removal of the Fmoc protecting group with 20% piperidine in DMF. The addition of the initial amino acid was confirmed by measuring the absorbance of the Fmoc protecting group at 275 nm and the presence of primary amine groups was confirmed with the ninhydrin assay after deprotection.Polyether-Peptide Soft Segment: The biodegradable peptide sequence GPQGIWGQG, selected based on high enzyme specificity and synthetic feasibility, was purchased from the Baylor Protein Chemistry Core Laboratory. The peptide was reacted with the amine-functionalized PEG utilizing standard coupling routes described above. Prior to coupling the peptide and polyether, amine-protected glycine was added to the C terminus of the peptide to prevent undesired coupling of the peptide segments. The structure of the resulting triblock copolymer, Peptide-PEG-Peptide, was confirmed using proton NMR and FTIR.Peptide-based Polyurethane ureas: Candidate polyurethanes were synthesized via a standard two-step reaction procedure. Briefly, hexamethylene diisocyanate was reacted with the free amine of polyether-peptide conjugates in the presence of stannous octoate catalyst. The butane diol chain extender was then added to build molecular weight. Polymer chemistry was confirmed with proton NMR and FTIR spectroscopy and molecular weight was determined with GPC analysis.Conclusion: In addition to providing new mechanobiology tools, these designer polyurethanes incorporate cell-responsive degradation into scaffold design. Current studies are ongoing to assess the mechanical properties, biocompatibility and biodegradation of these novel scaffolds.
9:00 PM - HH5.30
Self-assembly of Comb-rod Dendritic Block Copolymers as Tunable Drug Delivery Systems.
Shujun Chen 1 , Paula Hammond 1
1 Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractLinear-dendritic block copolymers combine the multi-functionality of dendrimers and the phase segregated morphological behavior of block copolymers. In this work, the aqueous self-assembly of a family of comb-rod dendritic block copolymers, which consists of a monodisperse alkyl-modified hydrophobic peptide rod block, poly(n-alkyl-L-glutamate) or PALG, and a biodegradable hydrophilic polyester dendron (PED) block, was investigated using dynamic light scattering (DLS), transmission electron microscopy (TEM), and cryogenic transmission electron microscopy (Cryo-TEM). Above the critical micelle concentration (CMC), as the concentration increases, the morphology of these PALG-PED copolymers changes from spherical micelles to cylindrical micelles to vesicles. Reducing the length of the linear PALG block shifts the micellar phase to higher concentrations. These amphiphilic biodegradable PALG-PED copolymers offer great promise as functional tunable drug delivery systems.
9:00 PM - HH5.31
Anodzied Titanium For Local Drug Delivery.
Chang Yao 1 , Thomas Webster 1
1 , Brown University, Providence, Rhode Island, United States
Show Abstract9:00 PM - HH5.32
Triterpene Saponin Glycosides Impact the Percutaneous Delivery of Water Soluble Drugs.
Christopher Pino 1 , Michael Scherer 1 , Chenxia Guan 2 , V. Shastri 1
1 Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, United States, 2 Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractPercutaneous absorption and transdermal delivery of water soluble drugs have proven to be challenging due to (a) their low permeability across lipid barriers and (b) due to the limited potential of traditional lipophilic chemical penetrations enhancers (CPEs) in providing appreciable enhancement. To date enhancement from water-based systems has been limited to ethanol/water, water/N-methyl pyrrolidone, binary systems with or without augmentation with surfactants. In an ongoing study, we have shown that triterpene saponin glycosides (TSGs) can significantly impact barrier properties of skin. In this study, we evaluated the effect of triterpene TSGs on the transport of water soluble anesthetics and cardiovascular drugs across full thickness pig skin. TSGs were found to enhance the permeability of water soluble anesthetics from 80 - 300% depending on physicochemical properties of the anesthetic, however, surprisingly appeared to be independent of molecular weight. More importantly the enhancement effects were observed at TSG concentrations (w/v %), that are considered too low for enhancement in typical CPEs. The reduction in CPE component in a formulation is important for reducing adverse dermatological reactions. TSG’s may represent a new class of CPE’s for water-based transdermal formulations.
9:00 PM - HH5.33
Design of a Bacteriophage for Targeted Delivery of an Antimicrobial Peptide.
Adam Hathorne 1 , Harry Bermudez 1
1 Polymer Science and Engineering, University of Massachusetts, Amherst, Amherst, Massachusetts, United States
Show AbstractBacteriophages as delivery vehicles offer an attractive option for treating microbial infections based on the highly specific nature of their cellular interactions and their ability to delivery genetic material into a cell. Unfortunately, the mechanisms controlling phage life cycle prevent their use as a stand alone treatment option. Our work is based around the design of a modified bacteriophage, which maintains specificity of infection while causing intracellular antimicrobial production and subsequent bacterial death. S. aureus has evolved a number of means to avoid the immune system and antimicrobial treatment. The S. aureus strain NCTC 8325 is well known to harbor at least three prophage elements: φ11, φ12, and φ13, within its genome. Maintaining these elements as prophage, or dormant phage, is essential for preventing cell lysis by the mature phage and is tightly regulated by the lysogeny module. The lysogeny module is transcribed from the antisense strand and produces a repressor protein which prevents transcription of phage genes. Therefore, a microbe containing prophage will be immune to infecting phage, given sufficient homology. A key element of our design involves incorporation of an antimicrobial encoding insert downstream of the lysogeny module such that transcription of the insert will not be prevented by repressor binding. We have successfully converted φ11 from dormant prophage to mature phage by way of UV irradiation. The phage was purified using a CsCl gradient and the DNA isolated by phenol:chloroform extraction. pUC19 will be used as a cloning vector, from which the insert may be removed and ligated into isolated phage DNA. Design of the insert is based around a modular assembly and contains two primary elements, a promoter and an antimicrobial. The promoter is inducible to control production of antimicrobial within the cell, and is optionally followed by a gfp reporter gene. Inclusion of the reporter is desirable both for indicating the relative level of infection as well as efficiency of transcription. For the antimicrobial we have chosen melittin and magainin as they have a broad spectrum of activity. In contrast to traditional strategies, intracellular antimicrobial production can achieve lethal concentrations with relatively small amounts of total peptide. Additionally, adjacent eukaryotic cells will experience lower effective concentrations due to their larger size, thus minimizing any undesired toxicity. While this work is focused around S. aureus, the design approach is applicable to any number of pathogenic bacteria, under the stipulation that there exists a bacteriophage capable of infecting the microbe.
9:00 PM - HH5.34
Raman Spectroscopy of Defected Griseofulvin in Powders and Films.
Anna Zarow 1 , Bo Zhou 2 , William Wagner 1 , Rodolfo Pinal 2 , Zafar Iqbal 1
1 , New Jersey Institute of Technology, Newark, New Jersey, United States, 2 , Purdue University, West Lafayette, Indiana, United States
Show Abstract9:00 PM - HH5.4
Functionally Graded Coatings for Wear Resistant Biomaterials: Characterization through Nanoindentation and Nanoscratch Tests.
Pasquale Vena 1 , Roberto Contro 1 , Dario Gastaldi 1 , Emanuele Bertarelli 1 , Carlo Bottani 2 , Marco Beghi 2 , Fabio di Fonzo 2 , Diego Tonini 2
1 Structural Engineering, Politecnico di Milano, Milano Italy, 2 Department of Chemistry, Materials and Chemical Engineering, Politecnico di Milano, Milano Italy
Show AbstractThe present work is an attempt to explore the application of Alumina thin coatings on metal substrates in the field of biomedical orthopaedic devices. Thus, homogeneous Alumina and functionally graded Alumina-Titanium coatings were deposited through the Pulsed Laser Deposition (PLD) technique on Silicon and Ti6Al4V alloy.The mechanical characterization allows forecasting the mechanical performance of the material when deposited on the articulating surface. The hardness (H) and the indentation modulus of the coating (Ei) are parameters of interest. Indeed, the wear behaviour is typically characterized by a large elastic strain to failure, which can be described in terms of the ratio between the hardness and the elastic modulus. Nanoscratch tests have been also performed with the purpose to evaluate the adhesion of coatings and the delamination mechanisms under severe wear conditions.Experiments were conducted using a NanoTest Indenter (Micro Materials Ltd., Wrexham, U.K.) with a diamond Berkovich indenter for nanoindentation and a diamond conical tip (radius 10 μm) for nanoscratch.Concerning nanoindentation, at least 10 multiload indentations (from 20 to 200 mN and from 220 mN to 500 mN, with 1 mN/s loading/unloading rate). A further multiple set of standard indentations was performed on all specimens with the purpose to collect data at small penetration depth (maximum load ranging from 3 to 10 mN, with 0.5 mN/s loading/unloading rate). Data were collected and elaborated accounting creep, thermal drift and machine compliance effects.Finite element analyses of the indentation tests allowed the identification of the elastic and inelastic constitutive parameters of the PLD Alumina coating. An axisymmetric finite element model with equivalent cone geometry has been developed. Nanoscratch tests were performed on Alumina coatings deposited on Silicon and Ti6Al4V alloy, with the aim to evaluate the tribological behaviour of coatings on different substrates. A multipass procedure was chosen to obtain precise information about the topography before, during and after the scratch. Scratches have been performed along a 500 μm linear path with constant scanning speed of 2 μm/s and a linear increasing load (5 mN/s). Tracks were analyzed by means of SEM imaging.In order to characterize the spatial gradient in composition, following the dimensional analysis, the load P can be represented by the dimensionless function P/(Erh2)=Π.The ratio P/h2=ErΠ has been measured for homogeneous alumina and FGM coatings. In an ideal experiment (perfect tip and homogeneous material), this ratio is a constant directly related to the hardness of the material. In this study, the P/h2 ratio clearly discriminates FGM coating, which exhibits a P/h2 ratio decreasing with depth.Nanoscratch tests have shown that coatings on titanium alloy substrate exhibit good adhesion properties and promising failure-resistant characteristics with respect to the coatings on silicon substrate.
9:00 PM - HH5.5
Electro-wetting and ArF Excimer Laser Induced Photochemical Surface Modification Formation of Hydrophilic and Hydrophobic Micro-domain Structure on IOL Surface for Blocking after Cataract.
Yuji Sato 1 , Kenji Kawai 2 , Mikio Sasou 3 , Hiroaki Ozaki 4 , Takeo Ooki 5 , Masataka Murahara 1
1 , Tokyo Institute of Technology, Tokyo Japan, 2 School of Medicine, Tokai University, Kanagawa Japan, 3 School of Medicine, University of Mie, Mie Japan, 4 School of Medicine, Fukuoka University, Fukuoka Japan, 5 School of Medicine, University of Tokushima, Tokushima Japan
Show AbstractA hydrophilic and hydrophobic micro-domain structure was formed photo-chemically on intraocular lens [IOL] surface with electro-wetting method, which improves the wet-ability applying the high voltage, and patterned ArF excimer laser irradiation. For this new method, the new IOL was developed to inhabit a fibrin attachment.1,490,000 intraocular lenses are implanted per year in the United State. A silicone rubber and poly methyl methacrylate [PMMA] have been used for IOL, contact lens and artificial cornea because of high transmittance in the visible region and superb mechanical modifiability. However, with time, fibrin is adsorbed onto the IOL surface to proliferate epithelial cells and causes the surface to get opaque, which results in a secondary cataract. Therefore, a new IOL that inhibits hindering secondary cataract and has high biocompatibility is required. A chemical, plasma and ion beam treatment methods are generally used for surface modification of biomaterials. However, in these methods, the original characteristics of the material are not exhibited because the sample surface has been damaged physically and it made easy for fibrin and cell to stick on the surface. On the other hand, the electro-wetting became the high wet-ability when the high voltage was applied between the water and the sample. When the high voltage impression was disconnected, however, the water contact angle restores itself to its original position. Thus, the IOL surface was selectively modified to be hydrophilic stable for long term by the ArF laser irradiation, when the IOL surface became the wet-ability to apply the high voltage, as the electro-wetting methods. The water was poured into the thin gap between the silica glass and the IOL with capillary phenomenon and applying direct current [D.C]. voltage between IOL and silica glass. In this condition, the ArF excimer laser light is projected through a patterned mask in reduced size. As a result, the micro-domains structure consisting of hydrophilic and hydrophobic groups arranged alternatively is photo-chemically created on the IOL. In order to evaluate the wettability of the modified sample, the contact angle with water was measured. The contact angle of water decreased from 110 degrees for the untreated silicone IOL to 50 degrees at the laser fluence of 30 mJ/cm2 and shot number of 30000. However, at the laser shot number of 5000 that reduced to 1/6, the water contact angle became to 50 degree applying the D.C. voltage of 6kV. Moreover the protein adsorption of the sample before and after treatments was also evaluated by scanning electron microscope [SEM] and infrared spectroscopy analysis [FT-IR], using fibrin [FIB] as a protein index in biocompatibility test. As the results, the fibrin adsorption rate on the modified IOL surface with 20-micrometer domains structure was reduced to one-fifth that of on the untreated silicone IOL and one-twentieth that of on untreated PMMA IOL.
9:00 PM - HH5.6
Tailored Scaffolds from a Gelatin-based Polymer System: Influence of the Molecular Architecture on Material Properties.
Axel Neffe 1 2 , Giuseppe Tronci 2 , Martin Roessle 2 , Andreas Lendlein 1 2
1 , Centre for Biomaterial Development and Berlin-Brandenburg Centre for Regenerative Therapies (BCRT), Teltow Germany, 2 , GKSS Forschungszentrum Geesthacht GmbH, Teltow Germany
Show Abstract9:00 PM - HH5.7
Controlled Actuation of Shape-Memory Polymer Networks by Application of Magnetic Field.
Muhammad Razzaq 1 , Marc Behl 1 , Karl Kratz 1 , Andreas Lendlein 1
1 Center for Biomaterial Development, Institute of Polymer Research, GKSS Forschungszentrum Geesthacht GmbH, Teltow Germany
Show AbstractShape-memory polymers have substantial innovation potential in different application areas, e.g. as intelligent implant materials in medicine or in smart textiles. Typically heat [1] or irradiation with light [2] is used to initiate the shape-memory effect. By incorporating magnetic particles in shape-memory polymers, a remote triggering of the shape-memory effect has been realized by inductive heating of these composites in an alternating magnetic field [3]. Potential applications for the magnetically-triggered shape-memory composites include smart implants and controlled medical instruments as they could enable surgeons to perform mechanical adjustments in a noncontact mode. Another area of applications could be on-demand drug delivery from an implanted depot, which could be triggered noninvasively by a magnetic field [4].Here we report on the controlled actuation of shape-memory polymer networks by application of an alternating magnetic field. Thermosets of shape-memory composites were prepared by crosslinking of oligo(ε-caprolactone)dimethacrylate in the presence of nanosized magnetite particles. The selected nanoparticles have a diameter of 90 nm and consist of an iron(III)oxide core coated with silica matrix. Effects of the reinforced magnetite particles on the thermal and mechanical properties of the polymer has been investigated by means of differential scanning calorimetry, dynamic mechanical thermal analysis as well as tensile and cyclic thermomechanical experiments have been carried out. The influence of the nanoparticles on the degree of crystallinity and elastic properties of the shape-memory polymer are discussed.In a dual shape programming process, temporary shapes of composites were obtained by elongating at increased environmental temperature (T > Tm,PCL) and subsequent cooling under constant stress. Actuation of shape-memory effect could be induced by inductive heating of composite samples in an alternating magnetic field (f = 258 kHz ; H = 30 kA.m-1). The maximum temperatures achievable by inductive heating depend on the specific magnetic field strength and the nanoparticle content. Shape-recovery rates obtained by magnetically-induced actuation are comparable to those reached by increasing the environmental temperature.[1] Lendlein, A. & Langer, R. Science, 296 (2002), 1673–1676. [2] Lendlein, A., Jiang, H., Jünger, O. & Langer, R. Nature 434 (2005), 879–882. [3] Razzaq, M. Y., Anhalt, M., Frormann, L. & Weidenfeller, B. Mater. Sci. Eng. A 444 (2007) 227- 235. [4] Mohr, R., Kratz, K., Weigel, T., Lucka-Gabor, M., Moneke, M., & Lendlein, A. Proc. Natl. Acad. Sci. USA 103(2006), 3540-3545.
9:00 PM - HH5.8
Liquid Phase Deposition of Nanoporous Titania on Spatially Organized Poly(p-xylylene) Films.
Niranjan Malvadkar 1 , Melik Demirel 1
1 Engineering Science and Mechanics, Pennsylvania State University, University Park, Pennsylvania, United States
Show AbstractNanoporous titania ia a potential biomaterial for bone prosthesis due to its superior osteoinductive and mechanical properties compared to conventionally prepared titania. In this talk, I present a novel method to prepare nanoporous titania using oblique angle polymerized (OAP) nanostructured poly(p-xylylene) (PPX) film [1] as a template. The OAP PPX film structure consists of 40 × 106 aligned nanocolumns (50-150 nm in diameter) per mm2 that are spatially organized on a silicon substrate [2]. The OAP PPX film has a mean surface roughness of 46.3 nm which is an order of magnitude higher than conventionally deposited PPX film [2]. We previously reported the preparation of OAP PPX/metal interfaces with enhanced adhesion using a ligand based electroless metal deposition technique [3,4]. Preparation of nanoporous titania is carried out using a two step process. First, the polymer surface is chemically functionalized using a ligand such as thiophenol or phenylphosphonic acid that binds to the polymer aromatic backbone via a mutual π-π interaction. Second, the nanoporous titania layer is deposited on the polymer surface by electroless reduction from ammonium hexafluorotitanate using boric acid as the reducing agent at 50 ○C. The adhesive properties of titania layer with the polymer film can be attributed to the superior ligand adsorption in the OAP PPX film.References:[1] Cetinkaya, M., Malvadkar, N., Demirel, M.C. Journal of Polymer Science Part B: Polymer Physics 46, 640-648 (2008).[2] Cetinkaya, A., Boduroglu, S. & Demirel, M. C. Polymer 48, 4130-4134 (2007).[3] Demirel, M. C., Cetinkaya, M., Singh, A. & Dressick, W. J. Advanced Materials 19, 4495-4499 (2007).[4] Malvadkar, N., Park, S., Wang, H., Macdonald, M., Demirel, M. C. Journal of Power Sources 182, 323-328 (2008).
9:00 PM - HH5.9
Active Cooperative Assemblies Towards Nanocomposites.
Muhammet Toprak 1 , Carmen Vogt 1 , Abhilash Sugunan 1
1 Functional Materials, Royal Institute of Technology, Stockholm Sweden
Show AbstractHollow microspheres that are composed of organic or inorganic shells are very important in biomedical and pharmaceutical applications. The ability to assemble materials that are organized over different length scales has a recognized importance for the development of new functional materials. In particular, the potential for application of emerging nanoscale objects can often only be realized by arranging such components into larger scale assemblies. In this work Complex coacervation is one phenomenon that presents new opportunities for single-step syntheses of ordered micron-scale objects that are composed from predefined nanoscale objects. This work demonstrates use of coacervation that utilizes PAA coated magnetic nanoparticles spontaneously assembling into hollow spherical structures in the presence of cations. These assemblies were then stabilized via cross-linking using EDA. It was also possible to utilize the coacervates’ chemical properties to form inorganic shell structures thus producing a calcium carbonate mineral shell confining magnetite nanoparticles. The resulting objects retain the original magnetic properties, and are robust under various conditions. We report on the fabrication route and thorough characterization of materials obtained at various stages.The financial support from Knut and Alice Wallenbergs Foundation (Toprak, No:UAW2004.0224)is thankfully acknowledged
HH6/DD3: Joint Poster Session: Materials in Tissue Engineering
Session Chairs
Elizabeth Orwin
V. Prasad Shastri
Tuesday AM, December 02, 2008
Exhibition Hall D (Hynes)
9:00 PM - HH6.1/DD3.1
Segmented Polyurethane Implants For Regeneration Of Esophagus.
Yerkesh Batyrbekov 1 , Nurzhan Bubeev 2 , Bulat Zhubanov 1
1 , Institute of Chemical Sciences, Almaty Kazakhstan, 2 , South Kazakhstan State Medicinal Academy, Chimkent Kazakhstan
Show Abstract9:00 PM - HH6.10/DD3.10
In Situ Mineralization of Block Copolymer Hydrogels.
David Griffin 1 , Surita Bhatia 1
1 Chemical Engineering, University of Massachusetts, Amherst, Massachusetts, United States
Show AbstractNanocomposites of hydroxyapatite in polymeric matrices have a number of important applications in bone and cartilage tissue engineering. Most studies to date have focused on systems where the polymeric matrix is a homopolymer gel or block copolymer solution. Use of a block copolymer hydrogel may offer additional control over crystallite size and morphology. Here we report on our efforts to synthesize hydroxyapatite in situ in block copolymer gels. Inorganic ceramic nanocomposites were formed by diffusion of calcium ions into a phosphate-containing Pluronic® F127 hydrogel. Initial pH of the gel prior to nucleation strongly influenced the final crystal structure and morphology. Nucleation at near physiological pH preferentially produced a highly crystalline calcium phosphate phase on the millimeter scale whereas mineral growth at alkaline conditions was found to produce hydroxyapatite crystals in the micrometer size range. Calcium phosphate mineral phases were determined by powder x-ray diffraction (XRD) and substantiated through energy dispersive x-ray spectroscopy (EDS). Morphology of the composites was examined using scanning electron microscopy (SEM). Rheological studies on these systems show that higher elastic moduli are obtained with composites prepared using the in situ synthesis technique as compared to conventionally prepared polymer-hydroxyapatite composites. The biomimetic nature of our investigation suggests that composites formed by this in situ technique my have significant biomaterial and drug delivery applications.
9:00 PM - HH6.11/DD3.11
Porous Hydroxyapatite/gelatin Scaffolds via Freeze-drying: the Effect of Bioceramic Nanoparticles on the Scaffold’s Microarchitecture and Properties.
Andrei Stanishevsky 1 , Sonda Sengupta 1 , Erin Ellis 1
1 , University of Alabama at Birmingham, Birmingham, Alabama, United States
Show Abstract9:00 PM - HH6.12/DD3.12
Biomimetic Chitosan/nano-hydroxyapatite Composite Scaffolds for Bone Tissue Engineering.
Wah Wah Thein-Han 1 , Jinesh Shah 1 , Devesh Misra 1
1 Center for Structural and Functional Materials, University of Louisiana at Lafayette, Lafayette, Louisiana, United States
Show AbstractWe describe here three dimensional biodegradable chitosan-nanohydroxyapatite (nHA) composite scaffold with improved mechanical, physico-chemical, and biological properties compared to pure chitosan scaffolds for bone tissue engineering. High and medium molecular weight chitosan scaffolds with 0.5, 1, and 2 wt.% fraction of nHA were fabricated by freezing and lyophilization. The nanocomposite scaffolds were characterized by a highly porous structure with interconnected pores and the pore size was similar for the scaffolds with varying content of nHA. The nanocomposite scaffolds exhibited greater compression modulus, slower biodegradation rate and reduced water uptake, but the water retention ability was similar to pure chitosan scaffolds. Favorable biological response of pre-osteoblast (MC 3T3-E1) on nanocomposite scaffolds includes improved cell adhesion, higher proliferation, and well spreading morphology in relation to pure chitosan scaffold. The study underscores chitosan-nHA composite as a potential scaffold material for bone regeneration.
9:00 PM - HH6.13/DD3.13
Towards Functional Biomaterials: Elucidating Design Principles of Enzyme Activated Hydrogelation.
Andrew Hirst 1 2 , Rein Ulijn 1 2 3
1 School of Materials and Manchester Interdisciplinary Biocentre, University of Manchester, Manchester, Lancashire, United Kingdom, 2 School of Materials, University of Manchester, Manchester United Kingdom, 3 School of Chemistry, University of Strathclyde, Glasgow United Kingdom
Show AbstractThe use of well-designed molecular building blocks, capable of forming self-assembled structures, is a fundamental construction principle for biological materials, with this approach being employed in various systems, ranging from double stranded DNA to complex structures such as the tobacco mosaic virus.[1] The appeal that nature holds, is that molecular scale information guides the organisation of complexity, expressed at the ‘system’ or materials level in terms of a specific function.[2] Intense activity has recently been devoted to the application of molecular recognition processes to control the formation of functional gel-phase materials, from simple molecular building-blocks. For example, regenerative medicine and tissue engineering using small molecule hydrogels as nanostructured scaffolds have been demonstrated to be genuine possibilities – for example, the regrowth of nerve cells has been recently demonstrated in vivo.[3] Therefore, to develop new technologies based on self-assembly, the ideal self-assembling material should have a simple synthesis, which is amenable to molecular design and can potentially be tailored for a broad range of applications. This presentation will focus on elucidating the self-assembly and hydrogelation properties of a small library of aromatic short peptide derivatives using microscopy, rheometry and thermal measurements.[4] These systems are based on several combinations of amino acid residues including Tyrosine, Valine and Leucine. Additionally, the peptides are modified with aromatic stacking ligands based on fluorenylmethoxycarbonyl (Fmoc). In each case, molecular self-assembly, which underpins macroscopic gelation is driven by exploiting an enzymatic hydrolysis process. Furthermore, the ability of the gel network structure to be modified by simply varying enzyme concentration will also be discussed. This offers an interesting perspective of fixing the chemical composition of the system, whilst modulating the gel materials properties. This strategy may offer a potential route to access new nanostructured materials applicable as three-dimensional (3D) scaffolds in which different morphological systems exert control over cell behaviour. [1] (a) K. van Workum, J. F. Douglas, Phys. Rev. E 2006, 73, 031502; (b) G. M. Whitesides, B. Grzybowski, Science 2002, 295, 2418-2421.[2] (a) M. Boncheva, G. M. Whitesides, MRS Bull. 2005, 30, 736-742; (b) I. W. Hamley, V. Castelletto, Angew. Chem. Int. Ed. 2007, 46, 4442-4455.[3] R. G. Ellis-Behnke, Y.-X. Liang, S.-W. You, D. K. C. Tay, S. Zhang, K.-F. So, G. E. Schneider, Proc. Natl. Acad. Sci. USA 2006, 103, 5054-5059.[4] (a) S. Toledano, R. J. Williams, V. Jayawarna, R. V. Ulijn, J. Am. Chem. Soc, 2006, 128, 1070-1071; (b) A. K. Das, R. Collins, R. V. Ulijn, Small, 2008, 4, 1279-1287.
9:00 PM - HH6.14/DD3.14
Hybrid Biomaterials with Tunable Elastic Modulus Through Sol-gel Functionalization of Peptidic Hydrogels.
Aysegul Altunbas 1 , Nikhil Sharma 1 , Radhika Nagarkar 2 , Joel Schneider 2 , Darrin Pochan 1
1 Materials Science & Engineering, University of Delaware, Newark, Delaware, United States, 2 Department of Chemistry & Biochemistry, University of Delaware, Newark, Delaware, United States
Show AbstractSol-gel chemistry was used to mineralize a pre-assembled peptide hydrogelscaffold for bone tissue engineering applications. The 20 amino acid peptideused in this study, MAX8, consisted mostly of alternating hydrophilic(lysine) and hydrophobic (valine) residues flanking a four amino acid turnsequence in the center (VKVKVKVKVDPLPTKVEVKVKV-NH2). After correctlyintramolecularly folding into a beta-hairpin conformation on addition of adesired solution stimulus, this peptide intermolecularly self-assembled intoa three dimensional network of interconnected fibrils rich in beta-sheetwith a high density of lysine groups exposed on the fibril surfaces.Polyamines are known to catalyze the polycondensation of silicic acid inwater. Therefore, the lysine-rich surface chemistry was utilized to createa silica shell around the fibrils. The mineralization process of the fibrilswas initiated by adding the silica precursor, tetramethyl orthosilicate, tothe pre-assembled hydrogel, which results in a rigid, porous silicate meshthat retains the microscale and nanoscale structure of the fibrillar peptidenetwork. Structural, mechanical, and in vitro biological properties of thesilicified hydrogels will be presented.
9:00 PM - HH6.16/DD3.16
Novel Composite Biomaterials Made from Resilin and Cellulose.
Shaul Lapidot 1 , Mara Dekel 1 , Sigal Meirovitch 1 , Sigal Roth 2 , Daniel Siegel 2 , Noa Lapidot 2 , Oded Shoseyov 1 2
1 The Faculty of Agriculture, Food and Environmental Quality Sciences, The Hebrew University of Jerusalem, Israel, Rehovot Israel, 2 , CollPlant ltd 2 Pekeris St. POB 2310 , Rehovot Israel
Show AbstractDespite the significant advance of tissue engineering and regenerative medicine, to date, resilient biomaterials that support load bearing tissue are still absent. Some of the top-performing natural bio-composite materials combine polymeric proteins with polysaccharides via Carbohydrate Binding Modules (CBMs) that enable introduction of both molecular order and interfacing between the composite components.The high affinity of carbohydrate binding modules (CBMs) proteins to cellulose allows their utilization for cellulose fiber modification and for cross-bridging between cellulose and other molecules. These properties led to the development of CBM technology that was applied in a wide variety of biotechnological applications. Previous work in our laboratory demonstrated the utilization of CBMs for both in-vitro and in-vivo cellulose fiber modification (Shoseyov et al, 2006). Resilin is a polymeric rubber-like protein secreted by insects to specialized cuticle regions, in areas where high resilience and low stiffness are required. Its unique mechanical properties allow the outstanding jumping ability of fleas, up to 30 cm high equivalent to a human high jump of 400 meters. Resilin binds to the cuticle polysaccharide chitin via a Chitin Binding Domain and further polymerized through oxidation of the tyrosine residues resulting in formation of di-tyrosine bridges and assembly of a high-performance protein-carbohydrate composite material. We report for the first time of the production of recombinant resilin-Cellulose Binding Domain (CBD) fusion protein that enable binding and polymerization of resilin on cellulose to obtain a new composite biomaterial. Assembly of novel composites made from resilin-CBD and different cellulosic materials such as whiskers (cellulose nano-crystals), regenerated cellulose films and fibers and their application as scaffolds for tissue engineering will be discussed. Reference:Shoseyov O, Shani Z, Levy I. (2006) Carbohydrate binding modules: biochemical properties and novel applications. Microbiol Mol Biol Rev. 70: 283-295.
9:00 PM - HH6.17/DD3.17
Modified Alginate for Biomedical Applications.
Soumitra Choudhary 1 , Surita Bhatia 1
1 Chemical Engineering, University of Massachusetts, Amherst, Amherst, Massachusetts, United States
Show AbstractHydrophobically modified alginate (HMA) was synthesized by condensation reaction with different alkyl amine (C8-C12) at low pH. At or above critical concentration, HMA forms a physical gel in aqueous media by hydrophobic interaction. Unreacted guluronic units of alginate can be further crosslinked with divalent cations, such as Ca2+. Interplay of the two different gelation mechanisms, hydrophobic association and chemical crosslinking, enables us to tune the rheological and mechanical properties of the system. Uniform gels were obtained by slow release of calcium ions from calcium-ethylene diamine tetra acetic acid complex with the addition of D-glucono-δ-lactone. Solubility of lipophilic drugs was found to be greatly improved compared to neat alginate presumably due to preferential uptake of the drugs by micelles formed by hydrophobic moiety. Controlled and extended release rate was observed for HMA due to stronger crosslinked alginate units surrounding the hydrophobic rich domains. Small angle scattering analysis and optical microscopy will be presented along with rheological data to determine the structure-property relationship of the resultant gels. Effect of hydrophobic chain length on structure and properties will also be presented.
9:00 PM - HH6.19/DD3.19
Hyaluronic Acid-gelatin Nanofibrous Scaffold Produced by Electrospinning of Their Aqueous Solution for Tissue Engineering Applications.
Ying Liu 1 , Richard Clark 2 , Lei Huang 3 , Miriam Rafailovich 1
1 Department of Materials Science and Engineering, SUNY at Stony Brook, Stony Brook, New York, United States, 2 Department of Biomedical Engineering, SUNY at Stony Brook, Stony Brook, New York, United States, 3 Department of Physics and Astronomy, SUNY at Stony Brook, Stony Brook, New York, United States
Show Abstract9:00 PM - HH6.2/DD3.2
Synthetic Platelets’ Role in Vascular Trauma and Their Interactions with Platelets.
James Bertram 1 , Nolan Flynn 2 , Erin Lavik 1
1 Biomedical Engineering, Yale University, New Haven, Connecticut, United States, 2 Chemistry, Wellesley College, Wellesley, Massachusetts, United States
Show AbstractUnder normal circumstances the body is able to maintain hemostasis. However, this intrinsic system is often insufficient due to pathologies or severe vascular trauma. Current treatments for aiding hemostasis are either limited by storage requirements, supply, or the nature of the injury. This brings to light the need for a non-immunogenic synthetic platelet substitute. An ideal platelet substitute would have minimal storage requirements, but more importantly, its hemostatic efficacy would not induce indiscriminant thrombosis. To address this need, we created a synthetic platelet substitute consisting of a nanosphere core comprised of a poly(lactic-co-glycolic acid)-poly(ε-carbobenzoxy-L-lysine) block copolymer (PLGA-PLL). Polyethylene glycol (PEG) terminated with the cell recognition motif arginine-glycine-aspartic acid (RGD) was conjugated to the core surface to finalize the synthetic platelet structure. Synthetic platelets’ interactions with rat platelets were analyzed in vitro. This platelet aggregation assay aided in the structural optimization of our synthetic platelet. To determine efficacy in vivo, we analyzed bleed/clot times in the rat vasculature following an intravenous injection of our synthetic platelet and its constituents. These injury models included a mechanical perturbation to the macrovasculature (femoral artery/vein) or a light-dye injury in the microvasculature (arterioles/venules). We observed that by varying the molecular weight of our PEG tether, thus varying the proximity of our RGD motif to the nanosphere surface, we were able to mitigate bleed times in the rat femoral artery in vivo as well as vary platelet affinity in vitro. This effect was found to be dose dependent as well. Our findings suggest that in an injured environment, where platelet aggregation is not the primary means of hemostasis (i.e. vasoconstriction is prominent in an artery/arteriole), synthetic platelets significantly augment clotting. These results imply that a synthetic platelet may be a feasible substitute for current treatments in facilitating hemostasis in an injured or pathological state.
9:00 PM - HH6.20/DD3.20
Iron Oxide Magnetic Nanoparticles for Treating Bone Diseases.
Nhiem Tran 1 , Thomas Webster 2
1 Department of Physics, Brown University, Providence, Rhode Island, United States, 2 Division of Engineering and Orthopaedics, Brown University, Providence, Rhode Island, United States
Show AbstractMagnetic drug delivery systems have drawn great interest from the medical research community in recent years. In this method, magnetic nanoparticles are prepared with modified surfaces and drug embedded coatings. These nanoparticles are later focused to the disease site by either an external magnetic field or an internal magnetic implant and, thus, results in improved drug effectiveness compared to other non-direct drug delivery methods. Our research goal is to prepare a magnetic drug delivery system that is capable of treating bone diseases such as osteoporosis. Results from this study provided evidence of increased osteoblast (bone forming cells) density in the presence of various coated magnetic nanoparticles compared to without nanoparticles. Magnetic nanoparticles of Fe3O4 and γ-Fe2O3 were synthesized via co-precipitation with ferrous (Fe2+) and ferric (Fe3+) ions by a base (NaOH) in an aqueous solution. Nanoparticles were characterized by transmission electron microscopy (TEM) and dynamic light scattering. All particles were magnetic with sizes ranging from 10nm to 20nm in diameter. The particles were further coated with calcium phosphate (CaP: the main inorganic component of bone) to tailor them to treat osteoporosis. To reduce nanoparticle agglomeration, a common problem encountered when using nanoparticles that decrease their effectiveness, these particles were coated in the presence of surfactants citric acid (CA), bovine serum albumin (BSA) and dextrant. Coated crystallites of CaP were controlled thermally to obtain highly crystalline hydroxyapatite or less crystalline CaP with and without hydrothermal treatment, respectively. TEM images showed that iron oxide nanoparticles were successfully embedded in the CaP particles. Osteoblast proliferation tests conducted after 1, 3 and 5 days showed that Fe3O4 particles coated in the presence of BSA significantly increased osteoblast density compared to the controls (no particles). While the mechanism for this is unclear at this time, it is important evidence showing that CaP coated magnetic nanoparticles increased osteoblast density, and, thus, could be useful to treat osteoporosis. For future studies, cell experiments with CaP, iron oxide and surfactants separately will be performed to understand the contribution of each factor to the osteoblast proliferation process.
9:00 PM - HH6.21/DD3.21
Drug Loaded Polypyrrole Coatings on Titanium for Supporting Bone Growth and Inhibiting Fibrosis.
Sirinrath Sirivisoot 1 , Rajesh Pareta 1 , Thomas Webster 2
1 Division of Engineering, Brown University, Providence, Rhode Island, United States, 2 Division of Engineering and Orthopaedics, Brown University, Providence, Rhode Island, United States
Show AbstractElectrically conductive polymers provide potentially interesting surfaces for bone implants because their surface properties can be versatile even releasing drugs immobilized by redox reactions. Specially, our previous research has demonstrated that carbon nanotubes grown out of nanotubular anodized titanium (Ti) can determine whether bone is occurring; such materials can also apply a voltage and increase bone formation. In this study, electropolymerization of pyrrole with drugs on Ti substrates were accomplished, providing a new cytocompatible surface for bone implants. Penicillin/streptomycin (P/S) and dexamethasone (Dex) were individually incorporated within the PPY thin film by cyclic voltammetry. The release of Dex was prolonged further by coating PPY film with poly(D,L-lactic-co-glycolic acid) (PLGA). X-ray photoelectron spectroscopy monitored and compared the reaction effectiveness and the yield of electropolymerization. Polypyrrole thin films with P/S and Dex, and even further coated with PLGA, all possessed nanometer scale roughness, as analyzed by atomic force microscopy. Preliminary in vitro results with human osteoblasts demonstrated greater adhesion after 4 hours on PPY-drugs embedded films, while the number of fibroblasts that adhered decreased compared to conventional Ti. A further step of this study was to evaluate drug release profiles. Such release of P/S and Dex from the polypyrrole film may inhibit infection and inflammation around hip/joint implants after surgery and the successful lyses of bacteria under a biofilm formed around a bone implant.
9:00 PM - HH6.22/DD3.22
Surface Modification Effect of Carbon Nanotubes-based Scaffolds on Human Embryonic Stem Cells Adhesion and Differentiation.
Tzu-I Chao 1 , Wei-Chun Chin 1 , Jennifer Lu 1 , Fang Lu 1
1 , University of California at Merced, Merced, California, United States
Show Abstract9:00 PM - HH6.23/DD3.23
Mechanical Behavior of Individual Bovine Marrow-derived Stem Cells Undergoing Chondrogenesis.
BoBae Lee 1 , Paul Kopesky 2 , Eric Vanderploeg 3 , Bodo Kurz 6 , Christine Ortiz 1 , Alan Grodzinsky 2 4 5
1 Materials Science and Engineering, MIT, Cambridge, Massachusetts, United States, 2 Biological Engineering, MIT, Cambridge, Massachusetts, United States, 3 Center for Biomedical Engineering, MIT, Cambridge, Massachusetts, United States, 6 Anatomisches Institut, Christian-Albrechts-Universität zu Kiel, Kiel Germany, 4 Electrical Engineering and Computer Science, MIT, Cambridge, Massachusetts, United States, 5 Mechanical Engineering, MIT, Cambridge, Massachusetts, United States
Show AbstractStem cell-based tissue engineering holds great potential for the regeneration and/or replacement of damaged cartilage. Mechanical studies of individual mesenchymal stem cells (MSCs) cultured in vitro can provide valuable insights into changes in intracellular morphology that accompany differentiation to the chondrocyte phenotype, as well as the synthesis of the cartilage-like neo-tissue during chondrogenesis. Here, we probe the temporal evolution of the single cell mechanical properties of bovine MSCs cultured within 3-D alginate scaffolds and stimulated to undergo chondrogenesis using dexamethasone and TGF-β1 for up to 10 days. Quasistatic indentation and force relaxation was carried out on each cell placed in a microfabricated silicon well using a spherical colloidal probe tip (end radius~ 2.5 μm) in an atomic force microscope in DMEM culture medium. Elastic moduli were calculated using a Hertzian contact mechanical model and time-dependent mechanical properties were estimated using a viscoelastic 5-element Maxwell-Weichert model. Dimethyl methylene blue (DMMB) dye binding and hydroxyproline assays were performed to quantify glycosaminoglycan and total collagen accumulation within the beads over time, respectively. The elastic modulus of bovine MSCs was found to be 575±56 Pa on Day 0 and stayed relatively constant up to day 10, and was lower than that of bovine primary chondrocytes (1000±112 Pa). Time-dependent mechanical properties of MSCs depended significantly on culture duration (ANOVA, p<0.05). At Day 3, MSCs exhibited instantaneous and quasi-equilibrium moduli which were significantly different from MSCs at Day 0 and 10. MSCs at Day 10 showed shorter τ1 (initial relaxation time constant) and longer τ2 (final relaxation time constant) compared to MSCs at Day 0 and 3. Notably, the final relaxation time constant for MSCs undergoing chondrogenesis was distinctly longer than that of primary chondrocytes even by 10 days, suggesting unique differences in intracellular organization and/or PCM that have not reached the final chondrocyte-like state. Variations in elastic modulus of MSCs during chondrogenesis were not detectable up to Day 10, while biochemical assays indicated that MSCs in alginate scaffolds synthesized and accumulated GAG and collagen in amounts comparable to MSCs in agarose and self-assembling peptide scaffolds as well as primary chondrocytes in alginate. This may be due to the fact that newly developing PCM of primary chondrocytes exhibits lower stiffness at initial culture duration. Further studies are being carried out on long-term culture of MSCs in alginate scaffolds up to 1 month to include mechanical testing using dynamic oscillatory compression.
9:00 PM - HH6.25/DD3.25
Cell Patterning Using Nanostructured Surfaces.
ChiungWen Kuo 1 , Jau-Ye Shiu 1 , Peilin Chen 1
1 Research Center for Applied Sciences, Academia Sinica, Taipei Taiwan
Show AbstractThe understandings of the cell-substrate interactions are important in many aspects including biocompatibility, cell culture, cell spreading and tissue engineering. It is recognized that the adhesion of cells on materials depends on surface characteristics such as hydrophobicity, surface charge, surface chemistry and roughness. Here we report a cell adhesion study on the nanostructured surfaces. Using a combination of nanosphere lithography and nanoimprinting, we were able to create nanostructures on various polymer surfaces, such as Teflon and polystyrene, without changing the surface chemistry of these polymers. In our approach, the nanosphere lithography was used to create close-packed well-ordered patterns. The size of the polymeric colloidal nanoparticles was trimmed by oxygen plasma treatment and followed by metal deposition. After the lift-off and deep etching process, nanohole arrays with desired depth could be obtained, which were then used the stamp in the nanoimprint process. By controlling the oxygen plasma etching time, the separation distance and the diameter of the holes could be adjusted, which in turn produced various types of polymeric nanopillars with surface water contact angle ranging from 120 degree to 160 degree. When these nanostructured surfaces were used to culture HeLa, 3T3, CHO and PC12 cells. It was found that all cells adhered preferentially on the roughened area allowing selective growth of cells on the desired area. Such nanostructured materials could be used as new materials for tissue engineering.
9:00 PM - HH6.26/DD3.26
Neural and Glial Cell Adhesion and Proliferation on Carbon Nanotube and Nanoparticle Zinc Oxide Polymer Composites.
Justin Seil 1 , Thomas Webster 1
1 , Brown University, Providence, Rhode Island, United States
Show Abstract9:00 PM - HH6.27/DD3.27
Photocurable Biodegradable Elastomers as Tissue Engineering Scaffolds.
Cody Schoener 1 , Christopher Perry 1 , Ranjini Murthy 1 , Melissa Grunlan 1
1 Biomedical Engineering, Texas A & M University, College Station, Texas, United States
Show AbstractThere is currently a deficiency of biodegradable tissue engineering scaffolds which exhibit the elastic nature of many soft tissues and which degrade homogeneously with subsequent linear loss in mechanical properties. Conventional thermoplastic biodegradable polymers such as poly (lactic acid) (PLA), poly (glycolic acid) (PGA) and their copolymers are generally brittle at physiological temperatures and degrade in a non-homogeneous fashion such that mechanical properties are dramatically diminished prior to significant loss of mass. Thus, thermoset elastomeric biodegradable polymers are promising candidates for scaffolds with mechanical properties more closely paralleling soft tissues and which degrade homogeneously. We have developed novel photo-crosslinked inorganic-organic elastomers as a new class of thermoset elastomeric biodegradable scaffolds for the regeneration of engineered soft tissues. Elastomers were prepared by photo-crosslinking of diacrylated triblock copolymers consisting of a central inorganic poly(dimethylisiloxane) (PDMS) block and terminal organic poly(caprolactone) (PCL) blocks. The impact of number average molecular weight (Mn) and PDMS:PCL ratio on mechanical properties, degradation behavior, and surface properties of the resulting elastomer were examined. The analogous porous elastomeric scaffolds were also formed in using a particle/leaching technique.
9:00 PM - HH6.28/DD3.28
Cytotoxicity and Biological Effects of Functional Nanomaterials Delivered to Various Cell Lines.
Meena Mahmood 1
1 Applied Science, UALR, Nanotechnology Center, Little Rock, Arkansas, United States
Show AbstractNanostructured materials have been found to be uptaken by various cell lines and highly affect their biological behavior. In this work, gold and silver metal nanoparticles as well as single wall carbon nanotubes were incubated separately and with apoptotic agents (Dexamethasne and Etoposide), in cell cultures of mouse long murine osteocytic bone cells (MLO-Y4 cells) and human cervical cancer cell line (Hela cells). The incubation of the nanomaterials with the cell cultures was carried out at two concentrations (0.5 X 10-9 M and 10-12 M) for 24 hours and the apoptotic agents (10-5 M and 75 X 10-6 M) were introduced for six hours. The cytotoxicity data revealed that the Au-NPs had a significant lower cytotoxic effect than the Ag-NPs and CNTs, values reflected by the percentage of the dead cells vs. living cells and that the combination of the nanomaterials and the apoptotic agents had a combinatorial effect, resulting in a significantly larger number of cells that died. The results highlighted by this study could represent a major development for the delivery of specific drug molecules into cancer cells and tumors by nanomaterials.
9:00 PM - HH6.29/DD3.29
Platelet Response on Poly (lactide-co-glycolic-acid) (PLGA) Film with Nano-structured Fillers.
Li Buay Koh 1 , Isabel Rodriguez 2 , Subbu S Venkatraman 1
1 School of Materials Science and Engineering, Nanyang Technological University, Singapore Singapore, 2 , Institute of Materials Research & Engineering, A*STAR (Agency for Science, Technology and Research), Singapore Singapore
Show AbstractThrombosis is a frequent complication associated with blood-contacting devices such as catheters and artificial stents. Current control of thrombus formation via the use of anticoagulant therapies is clearly not the best option, as complications can arise due to their usage. For that reason, a material with high level of blood compatibility is highly desirable. Platelet adhesion and activation on to the implant surface are crucial events in the formation of thrombus resulting from the interaction between the flowing blood and the foreign material. One of the parameters that have been shown to influence the adhesion of platelets is surface topography. In this work, we showed evidence that a nano structured polymer surface significantly reduces platelet adhesion as compared to pristine films. Nano-structured fillers were prepared on poly (lactide-co-glycolic-acid) (PLGA) films by infiltrating the PLGA solution into a nano porous anodized alumina (PAA) template. The inter-spacing between the nano-sized fillers and the aspect ratio proved to be the important parameters influencing the amount of platelet adhesion. The results illustrate that nanotopographic modifications of surfaces can elicit desired interfacial platelet response which is significant in the development for new polymeric blood-contacting materials with low thrombogenicity.
9:00 PM - HH6.3/DD3.3
Skin-external Device Integration using Expandable Cationic Poly(DMAA-co-AMTAC) Hydrogels.
Antonio Peramo 1 , Joong Hwan Bahng 2 , Cynthia Marcelo 3 , Nicholas Kotov 2 1 4 , David Martin 1 4 5
1 Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States, 2 Chemical Engineering, University of Michigan, Ann Arbor, Michigan, United States, 3 Surgery, University of Michigan, Ann Arbor, Michigan, United States, 4 Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, United States, 5 Macromolecular Science and Engineering, University of Michigan, Ann Arbor, Michigan, United States
Show AbstractThere has been a steady increase in the number of medical procedures with permanently implanted transcutaneous devices, which range from glucose sensors and catheters to more complex biointegrated prosthetics. A typical complication is the break-down of the skin around the device, but the most prevalent problem producing device failure arise from infection processes. These devices show high variability in their intrinsic properties, with a disparate number of material composition, surface structure, porosities and topologies. This variability hampers the investigation of a general solution for this unresolved problem.For this application, we were seeking to use a soft, biocompatible material inducing dermal and epidermal integration that could be produced as hydrogels with the form of scaffolds or deposited as coatings on a variety of substrates. We have been investigating the use of N,N-Dimethylacrylamide (DMAA) copolymerized with (3-Acrylamidopropyl)-trimethylammonium chloride (AMTAC) (poly(DMAA-co-AMTAC)) for its use in the integration of human skin with transcutaneous devices. This material has the interesting property that induces cell adhesion without the need of scaffold surface modification.Poly(DMAA-co-AMTAC) hydrogel scaffolds, fabricated using the inverted colloid crystal method, were used to observe their integration with human skin. Full thickness human breast skin explants discarded from surgeries were cultured from 5 to 10 days at the air–liquid interface using a Transwell culture system. Cylindrical, disks or other shaped hydrogels were placed inside the skin explants fitting the punctures produced by punch biopsies and full section histological analysis of the skin explants with the inserted hydrogel was then performed. In addition, separated hydrogel scaffolds were cultured up to seven days with either human fibroblasts or keratinocytes.Results indicate that poly(DMAA-co-AMTAC) hydrogels induce substantial extracellular matrix deposition by fibroblasts, maintain excellent dermal integrity in the contact areas with the skin and induce dermal fibers to completely integrate into the pores. Different types of cells remaining in the explants migrated into the scaffold pores, including red blood cells and fibroblasts and fibroblasts and keratinocytes adhered and colonized the separately cultured hydrogel scaffolds. Our results suggest that this type of soft, biodegradable material could be used as a general interface that induces skin integration with transcutaneous devices in contact with skin.
9:00 PM - HH6.30/DD3.30
Designing an Equivalent of the Corneal Extracellular Matrix by Investigating Corneal Fibroblast Response to Aligned Collagen Scaffolds.
Donna Phu 1 , Lindsay Wray 1 , Elizabeth Orwin 1
1 Engineering and Biology, Harvey Mudd College, Claremont, California, United States
Show AbstractThe extracellular matrix (ECM) of the native corneal stroma is comprised of highly-organized collagen nanofibers and corneal keratocyte cells. Our project aims to recreate the microenvironment of the corneal stroma by electrospinning aligned collagen type I fibers. Corneal stromal cells undergo specific phenotypic changes in response to wound healing. The quiescent keratocyte differentiates reversibly into a myofibroblast, characterized by the expression of alpha smooth muscle actin (α-sma), which is undesirable due to its contribution to corneal haze (Jester 1999). Preliminary studies in our lab have shown that corneal fibroblasts cultured in monolayer on aligned collagen mats express less α-sma than unaligned samples. The overall goal of this project is to test the ability of the monolayer scaffolds to build a three-dimensional construct that will support cell proliferation and maintain the transparent phenotype. In this study, we compare aligned and unaligned electrospun collagen substrates to standard substrate materials for application to recreating a native corneal stroma. Substrate materials were seeded with rabbit corneal fibroblasts and were assessed for α-sma expression by immunoflourescence staining and Western Blotting, and for cell stratification and overall transparency with Optical Coherence Microscopy (OCM). In addition to scaffold type, we investigated the ability of 2-O-α-D-Glycopryranosyl-L-ascorbic acid (G-Asc) to build a thicker scaffold. To assess the viability of this method, we measured intracellular protein expression, cell stratification, and construct transparency. Preliminary studies in our lab have shown that G-Asc may promote cell stratification and increase the number of cell layers better than cells cultured in normal media (DMEM, 10% fetal bovine serum and 1% antibiotic/antimycotic). However, G-Asc also upregulates α-sma expression in the cells and decreases the overall transparency regardless of scaffold type. For the aligned scaffolds, cells cultured in G-Asc media expressed more α-sma than cells cultured in normal media. However, cells cultured on aligned scaffolds still exhibited less α-sma than on other scaffold types relative to both media conditions. This suggests that culturing cells in G-Asc on aligned collagen scaffolds may provide a promising method to simultaneously obtain thicker scaffolds and downregulate α-sma expression.
9:00 PM - HH6.31/DD3.31
Bone Tissue Induction, using a BC-PCL Composite Scaffold Material.
Maria Cortes 1 , Filipe A. F. Macedo 1 , Ruben Sinisterra 2 , Alfonso Gala-Garcia 1
1 Restorative Dentistry, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil, 2 Chemistry, Universidade Federal de Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
Show AbstractAn artificial scaffold is required to be used in tissue engineering applications that can restore diseased or damaged bone to its natural state and function. Although autografts have all the desired characteristics with almost no disadvantage, the amount of autogenous bone that can be dissected from another host site is limited and difficult to shape. The aim of this study was prepared, characterized and evaluated the in vivo and in vitro response of composites of poly (ε-caprolactone) (PCL) and a bioceramic matrix (BC). The composites were prepared during the dissolution of the polymer phase in weight ratio 1:5 (polymer:bioceramic). Scanning electron microscopy (SEM) analysis revealed a characteristic surface of the interconnected porous scaffold. The X-ray diffraction shows pattern of BC-PCL composite where typical, PCL and BC peaks appeared in it. There were no others peaks nor peak shifts in the composite, suggesting that no chemical reactions occurred. The structure of the composite coating was analyzed using infrared spectroscopy, and characteristic structural bands of both BC and PCL were observed. In the current work, we investigated cellular viability, proliferation and morphology changes of rat primary culture osteoblasts in contact with BC-PCL composite. We observed that cell viability was increased in the composite when comparing with BC and control. We further found that collagen and alkaline phosphatase production was higher in osteoblasts cultured in the presence of BC-PCL compared to BC and control. In vivo experiments were performed after the analysis in vitro. In vivo analysis we used males Wistar rats, each animal received two different tablets implanted in a dorsal region under aseptic conditions following a triplicate assay. The mice were killed after 2 months and subcutaneous tissue treated with BC-PCL showed biocompatibility and all implants were surrounded by osteoblasts-like cells. In conclusion, BC-PCL had crystallinity characteristics with strong correlation between structure-activity and it was biocompatible in vitro and in vivo.
9:00 PM - HH6.32/DD3.32
Fabrication of Three-Dimensional Microfluidic Hydrogels by X-ray Lithography.
Chang Mo Jeong 1 , Ji Tae Kim 1 , Jung Ho Je 1 , Yeukuang Hwu 2 , Giorgio Margaritondo 3
1 X-ray Imaging Center, Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang Korea (the Republic of), 2 Institute of Physics, Academia Sinica, Taipei Taiwan, 3 School of Basic Sciences, Ecole Polytechnique Fadarale de Lausanne, Lausanne Switzerland
Show AbstractMicrofluidic hydrogels have been widely studied for tissue-engineering scaffolds because of their advantages such as mechanical strength, permeability, and biocompatibility (1). In particular, alginate-based microfluidic hydrogels are known to show a good transport of gases and nutrients through continuous networks in channel and therefore capable of tissue generation and growth in three dimension with appropriate permeation of biological growth factors (2). Particularly three-dimensional (3D) structures of microfluidic hydrogels with pervasive, interconnected channels are essentially required for biomimetic applications (2-3). The construction of 3D features however is still a challenge in conventional lithography such as photolithography and soft-lithography (4). In this study we present a novel strategy to fabricate 3D alginate-based microfluidic hydrogels using X-ray lithography. We demonstrate a successful fabrication of 3D microchannels with a few centimeter depths by an irradiation of X-rays (10-60 keV) from a synchrotron source. The 3D microchannel formation is attributed to fast scission of alginate hydrogels by X-ray irradiation. The microchannel depth is proportional to the X-ray irradiation time at a rate of 2 mm/min. We suggest that the X-ray-based strategy may provide a feasible method to fabricate 3D microfluidic hydrogels that would be potentially useful for widespread applications of tissue-engineering, microfluidic, and biotechnological systems.References:(1) J. A. Rowley, et al. Biomater. 20, 45 (1997).(2) M. Cabodi, et al. J. Am. Chem. Soc. 6, 908 (2007).(3) N. W. Choi, et al. Nature Mater. 6, 908 (2007).(4) D. Therriault, et al. Nature Mater. 2, 265 (2003).
9:00 PM - HH6.33/DD3.33
Fabrication of a Crosslinked Hydrogel Using Dense Gas Technology.
Nasim Annabi 1 , Suzanne Mithieux 2 , Anthony Weiss 2 , Fariba Dehghani 1
1 School of Chemical and Biomolecular Engineering, Sydney University, Sydney , New South Wales, Australia, 2 School of Molecular and Microbial Biosciences, Sydney University, Sydney , New South Wales, Australia
Show AbstractThe aim of this study was to fabricate a biopolymeric hydrogel using dense gas technology for tissue engineering applications. The hydrogel was synthesized through coacervation followed by crosslinking. Dense gas process facilitated coacervation, expedited cross-linking reaction, and induced porosity through the hydrogel matrix. The properties of fabricated hydrogel including pore sizes, pore interconnectivity, mechanical properties, and swelling ratio were tailored by pressure, temperature, processing time, and depressurization rate. The hydrogels fabricated using dense gas process exhibited superior properties compared with hydrogels produced at atmospheric pressure. The results of micro-CT scan and SEM images demonstrated that pore interconnectivity was substantially enhanced for fabricated hydrogel using dense gas process. Dense gas CO2 reduced the wall thickness and size of the pores. The cell adhesion and proliferation were remarkably increased for the samples fabricated using dense gas process. The cells were proliferated into the hydrogel matrix processed by the dense gas CO2 due to the formation of channels in the microstructure and nanosized fibrous features that were similar to collagen structures.
9:00 PM - HH6.34/DD3.34
Direct-Write Assembly of 3D Microperiodic Hydrogel Scaffolds for Tissue Engineering Applications.
Sara Parker 1 , Jennifer Hanson 1 , Robert Shepherd 1 , Robert Barry 1 , Roy Rotstein 1 , Pierre Wiltzius 1 , Ralph Nuzzo 2 , Jennifer Lewis 1
1 Materials Science and Engineering, University of Illinois, Urbana, Illinois, United States, 2 Chemistry, University of Illinois, Urbana, Illinois, United States
Show AbstractWe have fabricated three-dimensional microperiodic scaffolds by direct-write assembly of a concentrated ink, which is composed of poly(2-hydroxyethyl methacrylate) (HEMA) chains, HEMA monomer, crosslinker, photoinitiator, and water. The ink exhibits a viscoelastic response that enables it to flow readily during printing, yet retain its filamentary shape even as it spans gaps in the underlying layer(s). The scaffolds are patterned by extruding this ink through a fine deposition nozzle to form micron-sized hydrogel filaments that are periodically arrayed in three dimensions. After assembly, the printed scaffolds are cross-linked by UV exposure. 3D hydrogel scaffolds with features as small as 2 μm have been constructed. Poly(HEMA) scaffolds are then seeded with developing rat hippocampal neurons and imaged with fluorescence microscopy. We are currently investigating the cellular response to scaffold feature size and mechanical properties.
9:00 PM - HH6.35/DD3.35
Electrospun Poly(Vinilidene Fluoride) Nano Fibers for Electroactive Scaffolds.
Vitor Sencadas 1 2 , Jose Gomez Ribelles 2 3 4 , Manuel Monleon Pradas 2 3 4 , Senentxu Lanceros-Mendez 1
1 , University o Minho, Braga Portugal, 2 Centro de Biomateriales, Universidad Politecnica de valencia, Valencia Spain, 3 Regenerative Medicine Unit. , Centro de Investigación Príncipe Felipe, Valencia Spain, 4 , CIBER en Bioingeniería, Biomateriales y Nanomedicina, Valencia Spain
Show Abstract9:00 PM - HH6.37/DD3.37
Fabrication of Agarose Porous Scaffolds by X-ray Lithography.
Kyu Hwang Won 1 , Byung Mook Weon 1 , Jung Ho Je 1 , Yeukuang Hwu 2 , Giorgio Margaritonto 3
1 X-ray Imaging Center, Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang, Kyungbuk, Korea (the Republic of), 2 Institute of Physics, Academia Sinica, Taipei Taiwan, 3 School of Basic Sciences, Ecole Polytechnique Fadarale de Lausanne, Lausanne Switzerland
Show AbstractPorous scaffolds play a significant role in tissue engineering by preserving tissue volume, providing temporary mechanical function, and delivering biofactors (1). In particular agarose gels, which are chemically and electrically neutral materials, have been widely used in biomedical or biological research because of their biocompatibility and biomimetic capabilities in terms of water content, soft rubbery consistency, and low interfacial tension. Agarose-based porous scaffolds have extensively studied for potential applications of pancreas tissue engineering, cell-gel hybrids, nerve-guiding scaffolds, microcarriers for drug delivery or cell culture, and micropatterned stamping arrays (2). The applications require improved properties such as high porosity, proper pore size, biodegradability, mechanical strength, and toxicity. However optimizing all requirements remains a difficult challenge. A longstanding challenge is to design porous architectures with optimum porosity and mechanical strength. In this study we present a novel fabrication method that enables to easily build complicated agarose porous architectures using X-ray lithography. We reveal that a large volume of agarose hydrogels rapidly collapses by an irradiation of X-rays (10-60 keV). Using the X-ray-reactive volume collapse, we are able to fabricate agarose porous scaffolds of well-defined porous, interconnected structures with various channel widths and depths, which are respectively controlled by mask size and X-ray-reactive rate (~1mm/min). We suggest that X-ray-based strategy may provide a feasible way to easily fabricate complicated porous scaffolds for tissue engineering and biotechnology.References:(1) S. J. Hollister, Nature Mater. 4, 518 (2005).(2) J. Roman, et al. J. Biomed. Mater. Res. A 84, 99 (2008).
9:00 PM - HH6.4/DD3.4
Chemical Engineering of a Mesenchymal Stem Cell Homing Response.
Debanjan Sarkar 1 2 , Praveen Vemula 1 2 , Grace Teo 1 , Jeffrey Karp 1 2
1 Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts, United States, 2 Harvard-MIT Division of Health Sciences and Technology, Harvard Medical School, Boston, Massachusetts, United States
Show AbstractStem cell based therapies offer enormous hope for patients suffering from a wide range of diseases and disorders. Recently there has been significant interest in the clinical use of adult mesenchymal stem cells (MSCs), which are connective tissue progenitor cells. MSCs are currently in pre-clinical and clinical trials to treat several diseases. One of the greatest challenges in traditional stem cell therapy is to deliver a large quantity of viable stem cells with high engraftment efficiency. Unfortunately, MSCs home at a low efficiency; typically less than 1% of the infused cells reach the targeted site. The predominant reason why MSCs are thought to have low engraftment efficiency is due to the lack of relevant adhesion molecules on their surface Leukocytes, whose homing mechanisms have been well elucidated, depend on a range of adhesion molecules in a multistep homing process. The first step in the homing process involves reversible, adhesive interactions between glycoprotein receptors on specific circulating cells and ligands expressed on the surface of of the vascular endothelium. Several efforts have been made to modify MSCs by enzymatic and genetic methods to increase their homing efficiency but the efficacy of these modifications are limited due to the complexity and the potential safety concerns.To engineer a mesenchymal stem cell homing response, we employed a simple chemical approach. Specifically, the sialyl Lewisx (SLeX) moiety, found on the surfaces of leukocytes representing the active site of the P-selectin glycoprotein ligand (PSGL-1), was covalently immobilized to the cell surface by biotin-streptavidin conjugation to improve the homing response. Modified MSCs exhibited velocities of 2µm/sec at a wall shear stress of 0.366 dynes/cm2 which is 96% lower than the unmodified MSCs on P-selectin surface in a parallel plate flow chamber assay. Moreover, the flux value of the modified MSCs was 75 cells/mm2.sec whereas the unmodified cells displayed a value of 20 cells/mm2.sec. The lower rolling velocity and high flux value indicates that the MSCs modified covalently with SLeX have increased homing efficiency. Moreover, the MSCs’ native phenotype including its ability to proliferate and differentiate into multi-lineages was retained after the modification. Hence, MSCs with covalently conjugated SLeX moiety can potentially be targeted to inflammatory sites while preserving the normal cell phenotype. This platform approach offers a simple method to target potentially any cell type to specific tissues within the body through conjugation of specific targeting agents to the cell surface.
9:00 PM - HH6.5/DD3.5
Three-dimensional Hydrogel Structures with Submicron Scale for Biomedical Applications via Phase Mask Interference Lithography.
Ji-Hyun Jang 1 , Shalin Jhaveri 2 , Boris Rasin 1 , Christopher Ober 2 , Edwin Thomas 1
1 Institute for Soldier Nanotechnologies, Department of Materials Science and Engineering, , Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 2 Department of Materials Science and Engineering, Cornell University, Ithaca, New York, United States
Show AbstractA random terpolymer of poly(HEMA-co-MMA-co-MAA) has been synthesized and used as a negative-tone photoresist to generate bicontinuous 3D hydrogel structures at submicron scale. Phase mask interference lithography (PMIL) has been employed to fabricate three-dimensional hydrogel structures with high surface area. We have shown that the fully opened 3D hydrogel structures can be used as pH-responsive patterned polymer in drug-delivery system for the delivery of neurotrophins to enhance the performance of neural prosthetic devices.
9:00 PM - HH6.6/DD3.6
Electrical Stimulation of Nerve Cells: Image Analysis of Cell Behavior.
Kwang-Min Kim 1 , Julie Richardson 2 , Sung-Yeol Kim 1 , Celinda Kofron 2 , Diane Hoffman-Kim 1 2 , G. Tayhas Palmore 1 2
1 Division of Engineering, Brown University, Providence, Rhode Island, United States, 2 Division of Biology and Medicine, Brown University, Providence, Rhode Island, United States
Show AbstractNeurons of the central nervous system (CNS) encounter both permissive and inhibitory cues after injury. Conflicting results have been reported as to the benefits of electrical stimulation on neuronal outgrowth. To assess the therapeutic value of electrical stimulation, we aim to quantify how long and in which direction neuron processes extend when subjected to electrical stimulation. Toward this end, we have designed a platform with which to characterize the behavior of nerve cells during electrical stimulation. In this talk, the fabrication of this platform and its use in the study of electrically stimulated nerve cells will be described. The platform consists of two parallel chambers, which permits live-cell imaging of dorsal root ganglia (DRG) in the presence or absence (control) of electrical stimulation simultaneously. Electrical stimulation was applied to one of the two chambers containing adhered DRGs for 10 minutes at three different time points after initial cell plating. DRGs in both chambers were imaged during the electrical stimulation of one chamber and after removal of the electric field for one hour. Images were analyzed using MATLAB programming and FFT to compare the behavior of the neurons with and without electrical stimulation. Results from this analysis indicate that the mobility of both cell soma and neurites increases when electrically stimulated and tend to move in the direction of the applied field and neighboring cells. In addition to live-cell image analysis, cells were fixed and stained 25h after initial cell plating. Both length and angle of neurites were analyzed. Results from this analysis indicate electrical stimulation at an early stage of neuron culture had a negative impact on neurite outgrowth while electrical stimulation at an intermediate stage of the neuron culture had a positive impact on neurite outgrowth. Furthermore, neurites from these time points preferentially extended parallel to the direction of the electric field. Neurites stimulated at a late stage of culture, however, did not exhibit a significant difference in length and angle when compared to cells that were not electrically stimulated. This result suggests that some lag time post-electrical stimulation may be required to observe a difference in the length and direction of neurite extension. These results will be discussed in the context of a timeline of biochemical responses and their importance to nerve regeneration.
9:00 PM - HH6.7/DD3.7
Immunoreactivity of Self-Assembling Peptide-Polymer Biomaterials.
Jai Rudra 1 , David Hildeman 2 , Joel Collier 1
1 Department of Surgery, University of Chicago, Chicago, Illinois, United States, 2 Department of Immunobiology, Cincinnati Children's Hospital Medical Center, Cincinnati, Ohio, United States
Show AbstractMonday, 12/1New Presenter - Poster HH6.7/DD3.7Immunoreactivity of Self-Assembling Peptide-Polymer Biomaterials. Jai S. Rudra
9:00 PM - HH6.8/DD3.8
Different Macrophage Responses on Hydrophilic and Hydrophobic Carbon Nanotubes.
Young Wook Chun 1 , Dongwoo Khang 1 , Thomas Webster 1
1 , Brown Univ., Providence, Rhode Island, United States
Show AbstractPurified carbon nanotubes (with removed toxic catalytic particles) have been considered as novel materials for drug delivery and for generating artificial organs more efficiently due to their unique surface features. Traditionally, the surface chemistry of carbon nanotubes has been modified through various functionalization strategies to increase biocompatibility. Importantly, modulating the intrinsic material surface energy of carbon nanotubes (without functionalization, thus, establishing permanent, non degradable chemical, and physical surface properties) can potentially reduce an immune response mediated by macrophages. Herein, we report macrophage responses on different surface energy carbon nanotubes while keeping their nanoscale surface roughness. Specifically, interactions of ultra hydrophobic (bare or unmodified) and hydrophilic carbon nanotubes (due to the formation of oxide layers) with macrophages (including adhesion, proliferation, lipopolysaccharide (LPS) stimulation, hydrogen peroxide production and cytokine secretion (IL-1alpha, IL-1beta)) were investigated. All results clearly support the evidence that tailoring the surface energy of carbon nanotubes mediates a macrophage-dependent immune response while maintaining their ability to increase tissue growth, such as bladder tissue regeneration.
9:00 PM - HH6.9/DD3.9
Protein Adsorption can be Controlled by Varying PEG Block Length in PEG-containing Copolymers.
Arnold Luk 1 , Sanjeeva Murthy 1 , Wenjie Wang 2 , Hak-Joon Sung 1 , Joachim Kohn 1
1 New Jersey Center for Biomaterials, Rutgers University, Piscataway, New Jersey, United States, 2 Department of Physics, University of Vermont, Burlington, Vermont, United States
Show AbstractControlling the protein adsorption process on biomaterial surfaces is an important challenge for biomedical engineering. The performance of a medical device may be linked to the way proteins adsorb to its surface once it is implanted. It has been well documented that in random copolymer systems composed of hydrophobic units and PEG blocks, increasing the amount of PEG reduces protein adsorption and subsequent cell attachment. However, it is currently poorly understood how variations in the PEG block size affect polymer morphology and the subsequent protein adsorption process. To address this question, we prepared a system of three model polymers comprised of a hydrophobic monomer (desaminotyrosyl-tyrosine ethyl ester, DTE) which was copolymerized with PEG blocks of different molecular weights (100, 1000 and 35,000). In all polymers, we kept the total weight percentage of PEG constant at 40 weight %. Therefore, the only difference between these polymers was the PEG block length and the associated changes in polymer morphology. As expected for a PEG-rich polymer, we find that fibrinogen is repelled when the PEG block length is 1000. However, when PEG100 and PEG35k were used, fibrinogen adsorbs to the corresponding polymer surfaces readily. Analysis of the bulk materials using small angle neutron scattering (SANS) indicates that the copolymer with PEG35k blocks contains PEG domains with radii of about 10 nm separated by 33 nm between domains. In contrast, the copolymer with PEG1000 blocks had PEG domains with radii of about 5 nm separated by 15 nm between domains. Although the polymer containing PEG100 could have PEG-rich domains separated by > 70 nm, a distance that was at the limit of instrument resolution, it is most likely that PEG is homogeneously distributed at ~ 1 nm length scales. Since the dimensions of a molecule of fibrinogen are 47 nm x 4.5 nm x 4.5 nm, we speculate that the modulation of protein adsorption is caused by the spatial distribution of PEG domains: If PEG domains are sufficiently far apart, proteins will adsorb onto the hydrophobic DTE regions. This condition was met only for copolymers having PEG35k and PEG100 blocks. The data presented provide new insights into the mechanisms of surface-protein interactions and how these interactions can aid the rational design of biomaterials for tissue engineering.
Symposium Organizers
V. Prasad Shastri Vanderbilt University
Andreas Lendlein Institute of Polymer Research
LinShu Liu U. S. Dept of Agriculture
Samir Mitragotri University of California-Santa Barbara
Antonios Mikos Rice University
HH9: Tissue Engineering
Session Chairs
Wednesday AM, December 03, 2008
Room 310 (Hynes)
9:00 AM - HH9.1
Designing Enzyme-Triggered Hydrogels for Biomedical Applications Using Self-Assembling Octapeptides.
Elisabeth Vey 1 , Alberto Saiani 2 , Aline Miller 1
1 Manchester Interdisciplinary Biocentre, The University of Manchester, Manchester United Kingdom, 2 School of Materials, The University of Manchester, Manchester United Kingdom
Show AbstractStimuli-responsive, or smart, materials have received considerable attention recently due to their potential biomaterials applications in for example drug delivery, bio-sensing or regenerative medicine. There are a number of studies in the literature using pH, ionic strength, light or electric/magnetic fields as external stimuli to induce the self-assembly of small molecules into hydrogels for such biomaterials applications. Enzyme catalysis is one further class of stimuli that can induce changes in material properties. The class of enzymes called proteases are commonly known to hydrolyze peptide bonds. However, it has been shown that proteases can be encouraged to work in reverse when the peptide reaction product is thermodynamically stabilized relative to its precursors.Here we exploit such reverse hydrolysis to synthesize ionic peptides (containing alternating charged and non-charged amino acids) that are well known to self-assemble into β-sheet rich fibrillar hydrogels which have potential for tissue engineering applications. The key idea behind this is that we can start with a solution containing short, easy to synthesize peptides, namely FEFK, and simply use an enzyme, thermolysin, to couple the precursor peptides together which will result in a sol-gel transition and hence a 3-dimensional matrix ready for tissue regeneration applications.Solutions of FEFK were prepared by dissolving the tetrapeptide in water and adjusting the pH to pH 7 by adding concentrated NaOH. Thermolysin was subsequently added to the solution at a concentration of 0.3 mg mL−1. At low concentrations of peptide (≤ 50 mg mL−1), no increase in viscosity after addition of the enzyme was observed and the sample remained in a liquid state even after several days of incubation at 25°C. At high concentrations of FEFK (≥ 60 mg mL−1), clear, self-supporting gels formed at different times after addition of thermolysin depending on the concentration of peptides: the higher the concentration, the quicker the gelation.The resulting system was characterised using MALDI-TOF MS, HPLC, TEM, oscillatory rheometry, FTIR and SAXS. This revealed that hexa-, octa- and decapeptides all formed, with octapeptides forming preferentially. This is most likely due to the high self-assembling ability of the octapeptide, as once formed they will self-assemble and become trapped into β-sheet rich nanofibers that subsequently entangle to form a self-supporting hydrogel. Once trapped in this state the peptides are prevented from having any further reaction with the enzyme. A generalised model for such self-assembly will be described here and the effect of starting amino acid sequence will be discussed and correlated to final hydrogel properties.
9:15 AM - HH9.2
Novel Chitosan-Polygalactouronic acid-Hydroxyapatite Scaffolds For Bone Tissue Engineering.
Devendra Verma 1 , Kalpana Katti 1 , Dinesh Katti 1
1 Civil Engineering, North Dakota State University, Fargo, North Dakota, United States
Show AbstractIn the current work, we have synthesized a novel nanocomposite scaffold and evaluated it’s potential for bone tissue engineering. This scaffold was made using chitosan, polygalacturonic acid (PgA) and hydroxyapatite. Chitosan and PgA are both biocompatible, biodegradable and biofunctional biopolymers. They are also electrostatically complementary to each other. The strong interactions between negatively charged carboxylate groups of PgA and positively charged amino groups has shown to improve mechanical properties of Chitosan/PgA/hydroxyapatite based nanocomposites. The porosity of these scaffolds are about 97% and their elastic moduli and compressive strength are found to be 0.9 MPa and 0.023 MPa respectively. To evaluate their biological response, human osteoblast cells were seeded on films and also scaffolds of chitosan/PgA/hydroxyapatite nanocomposite. These nanocomposites have shown to promote cellular adhesion, proliferation and differentiation. After 10 days of seeding cells, osteoblast nodule formed on film samples and the size of nodule increased over time. Some of the nodules were as big as 700 μm. The mineral formation in these nodules was confirmed by staining them with alizarin red S. SEM images showed formation of collagen fibers by osteoblast cells in the nodule. Also, formation of collagen fibers was also observed in scaffolds. We present here the design of a novel nanocomposite system that may be used in bone tissue engineering.
9:30 AM - HH9.3
Microscale Heterogeneities Enhance Sarcomere Alignment and Contractile Force in Engineered Myocardium.
Adam Feinberg 1 , Crystal Ripplinger 1 , Sean Sheehy 1 , Kit Parker 1
1 School of Enigneering and Applied Sciences, Harvard University, Cambridge, Massachusetts, United States
Show Abstract9:45 AM - HH9.4
Poly(ortho ester amides): A New Family of Biodegradable Polymers for Drug Delivery and Regenerative Medicine.
Chun Wang 1 , Rupei Tang 1
1 Biomedical Engineering, University of Minnesota, Minneapolis, Minnesota, United States
Show AbstractWe have developed a method for synthesizing a new family of biodegradable materials based on poly(ortho ester amides) (POEAs). A diamine monomer containing a built-in ortho ester group was first synthesized and was then used to generate a polyamide backbone via polycondensation with a diacid. Our synthetic pathway overcomes some of the drawbacks of the traditional polymerization methods of poly(ortho esters) and opens up new venues to a wide variety of polymer main-chain structure with tunable bulk properties and biodegradability. Three POEA polymers were synthesized using diacid monomers of various chain-length (C8, C10, C12) and characterized by NMR, GPC, and TGA. Interestingly, these polymers formed gels in selected solvents (including water) and underwent temperature-responsive, reversible sol-gel transition, presumably due to hydrogen bonding between amide groups on the backbone of the POEAs and the solvents. The temperature-sensitive phase behavior of the polymers is closely related to the diacid monomer composition. POEA hydrogels formed in water as well as POEA organogels formed in organic solvents were hydrolysable as verified by weight loss over a period of time at pH 7.4. Acceleration of hydrolysis in slightly acidic pH medium (pH 5) was observed, presenting a potential mechanism for pH-triggered drug delivery from polymer gels. To establish the feasibility of drug release from the POEA hydrogels, fluorescently labeled dextran was used as a model drug and incorporated into the hydrogels and the release kinetic of the model drug was determined. Incubation of cells cultured in vitro with either direct physical contact with the hydrogels or in contact with polymer extracts suggest that the materials have excellent cell compatibility. Organogels of POEA were processed into porous 3-dimensional scaffolds and were capable of sustaining the adhesion and growth of cells. In conclusion, we report a novel, straightforward methodology for chemically synthesizing acid-labile biodegradable polymers, which combines the strengths of poly(ortho esters) and polyamides and overcomes some of the drawbacks of the two polymers. Preliminary studies have shown that these temperature-sensitive biodegradable polymers can be used to release model drugs or to serve as cell scaffolds in regenerative medicine.
10:00 AM - HH9.5
Design and Fabrication of a PDMS-based Neuroelectrical Interface for Peripheral Nerve Repair.
Teresa Adrega 1 , Mark Blamire 2 , Stéphanie Lacour 1
1 , Nanoscience Centre, Cambridge United Kingdom, 2 , Department of Materials Science, Cambridge United Kingdom
Show AbstractA cut peripheral nerve cell has the spontaneous ability to regenerate proximal to the cut, and to grow until it finds a suitable target structure to form a functional connection. However the regenerated nerve cells often connect to the wrong targets leading to limited functional recovery.We have recently proposed a novel implant design for a regenerative neuronal interface for peripheral nerve repair. It consists of a 3D array of parallel microchannels made with flexible and biocompatible material with embedded electrodes. The interface gives mechanical guidance through the channels for the regeneration of injured nerve fibres and also allows the stimulation/recording of electrical signals. Ultimately, the microelectrode array may be used as the interface between the injured nerves of an amputee’s limb and a computerized prosthesis.We have developed an initial prototype of such a device using polyimide as the structural material. But to improve the implant biomechanical compatibility, i.e. the mechanical properties of the artificial structure should be as similar as possible to those of nerve cells, we are exploring the use of softer polymers: silicones. Nerve cells have a Young’s modulus range of 0.1-1 kPa. Whilst the Young’s modulus of polyimides is of a few GPa, that of silicones such as Polydimethyl siloxane (PDMS) is in the 0.1-1 MPa range. We now present the design and fabrication process of a PDMS based neuroelectronic interface for implantation on the PNS. The proposed implant is fabricated using microsystem technology in clean-room environment. Gold electrodes are defined on a PDMS (Sylgard 184, Dow Corning) substrate and encapsulated using a 5 microns-thick UV photosensitive PDMS (silicone WL5351, Dow Corning) with opened electrical access sites. The direct patterning of both electrodes and encapsulation layer allows high spatial selectivity. The design comprises an array of 20 electrodes, 50 microns wide separated by 50 microns spaces. A second UV photosensitive PDMS (silicone WL5150, Dow Corning) is used to define parallel channels via photolithography on top of the encapsulation layer. The channels are 100 microns wide, 100 microns deep and 3 mm long. The final step of the process consists of rolling the planar device transversely to the channels. Doing so we obtain a 3 mm diameter 3D array of closed and densely packed microchannels mimicking the nerve anatomy. Impedance measurements of the electrodes were performed in physiological fluid in the 100 Hz to 100 kHz range and show that the gold electrodes remain functional after the rolling procedure. The impedance at 1 kHz is approximately the same before and after the rolling and has an average value of 400 kΩ. We will present details on the fabrication process of the PDMS based device and the electrical characterization of the flat and rolled micro-electrodes.
10:15 AM - HH9.6
Mechanical Properties of Peptides Forming b-sheet Fibrils can be Controlled Through a Rational Choice of the Amino Acids and Modifying the Environmental Conditions Around Those Fibrils.
Lorenzo Aulisa 1 , Jeffrey Hartgerink 1
1 Chemistry, RICE University, Houston, Texas, United States
Show AbstractMolecular self-assembly is a powerful strategy to prepare useful nanostructured materials. We will describe a well-known biological motif, the peptide beta-sheet, used to design short oligopeptides able to self assemble in long nanofibers organized in a well defined and entangled network. All the peptides used in this work,are engineered into an ABA block motif in which block B is organized in alternating hydrophilic and hydrophobic amino acids. In this way, when dissolved in water, the peptides quickly assemble in a way that allows the hydrophobic amino-acid to be excluded from the aqueous environment, while the hydrophilic one is exposed to that. Once the first dimer is formed, intermolecular backbone hydrogen bonding can quickly take place with other dimers leading to the formation of long fibers. The A block of the peptide is characterized by a variable number of charged amino-acids such as lysine or glutamic acid. At neutral pH, the charged block A works against the B block, controlling the length of the fiber and therefore also improving noticeably the water solubility of these fibers. We have found that through a rationale choice of the hydrophilic amino acid, in the B block, and the charged one, in the A block, it is possible to trigger the mechanical properties of the fiber network, going from a weak gel to a much stronger one. By choosing carefully the peptide primary structure, it is possible to create gels having designed mechanical and physical properties that could be used in many different applications.
10:30 AM - HH9.7
Atomistic Molecular Modelling of Polymeric Biomaterials and Surface Activities of Bioactive Molecules.
Dieter Hofmann 1 , Maria Entrialgo 1 , Jutarat Pimthon 1 , Regine Willumeit 2 , Andreas Lendlein 1
1 Institute of Polymer Research, GKSS Research Centre, Teltow Germany, 2 Institute of Materials Research, GKSS Research Centre, Geesthacht Germany
Show Abstract10:45 AM - HH9.8
Optical Tweezers and Microfluidics for Live Cell Lithography.
Jan Scrimgeour 1 , Utkur Mirsaidov 1 , Winston Timp 2 , Mustafa Mir 1 , Gregory Timp 1
1 Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States, 2 Whitehead Institute, Massachusetts Institute of Technology , Cambridge, Massachusetts, United States
Show AbstractThree essential components of living tissue are living cells, a scaffold, and external signals—arranged into a complex array that dictates its function. Synthetic tissue should capture the complexity of this in vivo environment to elicit tissue-specific features, while still affording some exogenous control of the microenvironment of each cell. The complexity of the in vivo microenvironment is defined in part by the social context that develops from the tissue architecture, i.e. the communication between cells, and between cells and the local scaffold that modulate cellular responses. This complexity is indispensable in models for drug discovery, which is why the assays used so prevalently are based on tissue from animals despite the cost, lack of availability and irreproducibility. We have developed a new technique for generating synthetic tissue that has the potential to capture the three-dimensional (3D) complexity of a multi-cellular organism with submicron precision. Using laminar flow in a microfluidic network, we convey cells to an assembly area where a combination of multiple time-shared and holographic optical tweezers are used to organize them into a complex array. The cells are then encapsulated in a 30 μm × 30 μm × 45 μm volume of photopolymerizable hydrogel mimicking an extra-cellular matrix. To extend the size, shape and constituency of the array with minimal loss of viability we then step to an adjacent location while maintaining registration with the reference array, and repeat the process. Using this step-and-repeat technique, we formed a heterogeneous array of E. coli genetically engineered with a lac switch that is functionally linked to fluorescence reporters. We then induced the array using ligands introduced through the microfluidic network and followed the space-time development of the fluorescence to evaluate metabolic activity where more 80% cells were alive. Cell-to-cell signaling within the hydrogel construct is also demonstrated. Thus, the step-and-repeat method fills an important niche in the continuum between the complex and highly variable data provided by animal models and tissue samples and the reductionist in vitro cellular assay data.
11:00 AM - HH9: TISSENGR
BREAK
HH10: Controlling Stem Cell Function
Session Chairs
Wednesday PM, December 03, 2008
Room 310 (Hynes)
11:30 AM - **HH10.1
Steering Stem Cell State and Fate – Merging Developmental Biology with Bioprinting, Substrate Properties and Novel Drug Delivery Devices.
Ola Hermanson 1
1 Dept Neuroscience, Karolinska Institutet, Stockholm Sweden
Show AbstractStem cells hold great promise in therapeutic applications, including cell therapy and regenerative medicine, and also give the opportunity to increase the understanding for and improve the diagnosis and clinical treatment of many types of disease, including cancer, psychiatric and neurodegenerative disease. My lab with collaborators have developed methods for and are elucidating epigenetic and transcriptional mechanisms regulating the differentiation of rodent embryonic neural stem cells into the most common forebrain cell types, including functional pyramidal glutamatergic neurons, GABAergic interneurons, astrocytes, mesenchymal cells and oligodendrocytes (e.g., Nature 450 (2007) 415-9), and we are currently in collaboration applying these conventional differentiation protocols on human embryonic stem cells.Yet the clinical use of stem cells are hampered by many problems including cell survival, potential overgrowth, and the integration into functional circuits in vivo. Further whereas functionality of neurons and neural cells derived from stem cells are validated by several parameters, including morphology, gene expression, and electrical properties, the development of functional neural circuits in vitro is needed for increased knowledge of molecular and genetic etiology of disease.The possibilities of using biomaterials and hydrogels for improved results in stem cell therapy and tissue engineering are well recognized. Here I will discuss the most recent advances from our lab and our collaborators in using bioprinting and bioelectronics to steer and monitor multipotent stem cell differentiation. We have demonstrated that using bioprinting with a conventional bubble jet printer to print macromolecules on polyacrylamide-based hydrogels is an effective approach to steer neural stem cell differentiation and to create functional gradients (Biomaterials 28 (2007) 3936-43). Current experiments involve using bioprinting approaches to administer membrane-bound molecules critical for stem cell characteristics, such as Notch and Eph ligands, as well as other biomedical applications. We have further found that whereas neural stem cells, conventionally grown on polystyrene-based cell culture plates, retain their plasticity on various materials such as PDMS, PVC, and PEDOT, the properties of the materials along with the substrate stiffness have major and unexpected effects on the stem cell differentiation. We are in addition developing and evaluating novel macromolecule delivery devices, such as “morphogenerators”, to in combination with the molecular protocols, bioprinting and appropriate substrate properties will improve the control of stem cell differentiation into functional cells and circuits, and also provide novel approaches to complementary treatment of cancer disease, including tumors in the central nervous system.
12:00 PM - HH10.2
Self Assembled Monolayers Studies on Gold for Cortical Neuronal Cell Immobilization.
Olena Palyvoda 1 , Hitesh Handa 2 , Andrey Bordenyuk 3 , Erik McCullen 1 , Achani Yatawara 3 , Alexander Benderskii 3 , Yuri Danylyuk 1 , Gregory Auner 1 4
1 Department of Electrical and Computer Engineering, Wayne State University, Detroit, Michigan, United States, 2 Department of Chemical Engineering and Material Science, Wayne State University, Detroit, Michigan, United States, 3 Department of Chemistry, Wayne State University, Detroit, Michigan, United States, 4 Department of Biomedical Engineering, Wayne State University, Detroit, Michigan, United States
Show AbstractThe significant challenge in the development of miniaturized biocompatible neuroprosthetic devices lies in understanding how neuronal networks grow on and interact with the implant surface. Self Assembled Monolayers (SAMs) have emerged as promising candidates for defining material features on miniature scales. In this work we characterize cortical neuron adhesion, growth, and distribution depending on the molecular structure and composition of an adhesive layer. Neuron adhesion efficiency was studied for amino-terminated, carboxy-terminated and 1:1 mixed alkanethiol SAMs deposited on gold substrates. To assess the suitability of SAMs for neuronal growth, we have investigated correlations of neuron adhesion with the chemical structure at the SAM surface characterized by Sum Frequency Generation (SFG) vibrational spectroscopy and with the roughness of gold substrate and thickness of SAM monolayers studied by XPS and AFM. The optical properties of the films are investigated using spectrophotometric measurements of the absorbance transmittance and reflectance in the UV-VIS-NIR wavelength ranges. Neuronal cell growth was monitored using Fluorescent Microscopic imaging, showing that only amino-terminated SAMs support growth of neuronal networks. We conclude that the neuronal cells adhesion is not critically affected by the surface roughness within 0.7-2 nm range or details of the molecular ordering and orientation of the terminal amino groups, but only on the chemical functionality displayed at the surface. This approach can be used to create new methods that help map structure-property relationships of biohybrid systems.
12:15 PM - HH10.3
Development of Novel Thermally Responsive, in Situ Crosslinkable Hydrogels for Tissue Engineering.
Leda Klouda 1 , Michael Hacker 1 , Laura Barg-Walkow 1 , James Kretlow 1 , Antonios Mikos 1
1 Bioengineering, Rice University, Houston, Texas, United States
Show AbstractInjectable hydrogels provide promising carriers for cell and drug delivery in tissue engineering due to their hydrophilic nature, minimally invasive method of delivery and the ability to fill irregular defects. Thermally responsive hydrogels have the advantage of using temperature as the stimulus for their solidification. They can be liquid at ambient temperature, and gel upon injection in the human body while temperature increases to physiological levels. In this study, we have developed injectable hydrogels with controllable properties that gel in situ with two independent, physical and chemical mechanisms, namely lower critical solution temperature behavior and chemical crosslinking. Moreover, we hypothesized that the introduction of hydrophobic core molecule will enhance the mechanical cohesion of the hydrogel. Macromers were synthesized from pentaerythritol diacrylate monostearate, N-isopropylacrylamide, acrylamide and 2-hydroxyethyl acrylate by free radical polymerization. At a next step, the free hydroxyl groups on the macromers were (meth)acrylated to add functionalities for chemical crosslinking. Macromer composition was characterized by NMR spectroscopy, differential scanning calorimetry, and oscillating rheology was employed to characterize the thermally induced phase transition and the resulting gels. Correlations between the composition of the macromers, including the degree of modification with (meth) acrylate groups, and the transition temperature as well as the cytocompatibility were established. Cell viability was high for up to six hours for most formulations; however higher degrees of modification on the (meth)acrylated macromers increased toxicity at 24 h. Moreover, acrylated macromers seemed more cytocompatible than the corresponding methacrylates. Chemically crosslinked hydrogels were fabricated with the addition of a cytocompatible thermal initiator system. The resulting hydrogels were more stable over time compared to gels that formed by a physical mechanism only. This design enables for gels that solidify fast at 37°C due to physical gelation and subsequently slowly crosslink to allow for increased stability with no adverse effects on encapsulated cells.
12:30 PM - HH10.4
Degradation of and Angiogenesis around Multiblock Copolymers Based on Poly(p-dioxanone)/poly(ε-caprolactone) Subcutaneously Implanted in Pharyngeal and Dorsal Regions of the Rat Neck.
Bernhard Hiebl 1 , Rosemarie Fuhrmann 2 , Friedrich Jung 1 , Steffen Kelch 1 , Andreas Lendlein 1 , Ralf-Peter Franke 1 2
1 Center for Biomatrerial Development and Berlin Brandenburg Center for Regenerative Therapies (BCRT), Institute for Polymerresearch, GKSS Research Center GmbH, Teltow Germany, 2 Central Institute for Biomedical Technique, University of Ulm, Ulm Germany
Show Abstract12:45 PM - HH10.5
Skeletal Muscle Cells Differentiation on Polyelectrolyte Multilayer Films of Controlled Stiffness.
Catherine Picart 1 , Kefeng Ren 1 , Thomas Crouzier 1 , Christian Roy 1
1 Biology and Health, Université de Montpellier 2, Montpellier France
Show AbstractMechanical properties of model and natural gels have recently been demonstrated to play an important role on various cellular processes such as adhesion, proliferation and differentiation, beside events triggered by chemical ligands. Understanding the biomaterial/cell interface is particularly important in many tissue engineering applications and in implant surgery. One of the final goals would be to precisely control cellular processes at the biomaterial surface and to guide tissue regeneration. In this work, we investigate the “substrate mechanical effect” on cell adhesion for thin biomimetic polyelectrolyte multilayer (PEM) films containing hyaluronan, a natural component of extra-cellular matrices. Poly(L-lysine)/Hyaluronan (PLL/HA) films of controlled thickness (1 µm) and of tunable stiffness were prepared by cross-linking the films with a water-soluble carbodiimide (EDC) to form covalent amide bonds. Both quantitative Fourier Transform Infrared Spectroscopy (FTIR) and AFM nano-indentations were performed to bring chemical information on the film structure and on its mechanical properties. We thus determined the % of carboxylic groups involved in crosslinks and the film Young’s elastic modulus (E0). The modulus was varied over two orders of magnitude from 3 kPa to 400 kPa by varying the EDC concentration. Other film properties (roughness, hydrophilicity, protein adsorption) were found to be moderately affected by cross-linking. The C2C12 cells were chosen as model cells as this cell line is already widely used for studies of muscle biology and regeneration. Myogenic differentiation on control tissue culture polystyrene surfaces is a well understood process in terms of the sequence of events and protein expression. In growth medium, we found that adhesion and proliferation are greatly enhanced when film stiffness is increased. After switching to differentiation medium, we evidenced that C2C12 cell differentiation was also greatly dependent on film stiffness. Cells differentiated on all films but the morphology of the myotubes exhibited striking differences depending on the extent of cross-linking. On soft films, myotubes were very short and thick and differentiation could only be maintained for few days. On stiffer films, significantly more elongated and thinner myotubes could form and grow for up to ~ 2 weeks. Myotube striation was also increased for the highly cross-linked films. These results indicate that substrate mechanics of thin films is an important parameter influencing cellular processes and that PEM offer a new way to prepare biomimetic thin films of tunable mechanical properties with additional possibilities for bioactive molecule loading. These PEM films could also find applications in the fields of regenerative medicine and muscle/cardiac tissue engineering, where controlling the cell/material interactions is crucial for guiding the cellular response.
HH11: Advanced Materials for Imaging
Session Chairs
Wednesday PM, December 03, 2008
Room 310 (Hynes)
2:30 PM - **HH11.1
New Materials for Imaging and Treating Inflammatory Diseases.
Niren Murthy 1
1 , Georgia Tech, Atlanta, Georgia, United States
Show AbstractInflammatory diseases cause millions of deaths each year and new strategies for treating and diagnosing inflammatory diseases are greatly needed. In this presentation two new materials will be presented, which are designed to enhance the treatment and diagnosis of inflammatory diseases, termed the polyketals and the peroxalate nanoparticles. The polyketals are acid sensitive polymers that degrade into neutral compounds and generate minimal inflammatory responses in vivo. Polyketal microparticles can enhance the treatment of inflammatory diseases by targeting therapeutics to macrophages and by acting as controlled release reservoirs. In this presentation I will present our recent in vivo data demonstrating that polyketal microparticles loaded with p38 inhibitors can improve cardiac function following a myocardial infarction, and also that polyketal microparticles loaded with siRNA targeting TNF-alpha can rescue mice from acute liver failure. The second class of materials that will be presented are a new family of hydrogen peroxide sensing contrast agents, termed the peroxalate nanoparticles. The overproduction of hydrogen peroxide is implicated in the development of numerous inflammatory diseases and there is currently great interest in developing contrast agents that can image hydrogen peroxide, in vivo. In this presentation, we demonstrate that nanoparticles formulated from peroxalate esters and fluorescent dyes can image hydrogen peroxide in vivo with high specificity and sensitivity. The peroxalate nanoparticles have several attractive properties for in vivo imaging, such as tunable wavelength emission (460-630 nm), nanomolar sensitivity for hydrogen peroxide and excellent specificity for hydrogen peroxide over other reactive oxygen species. The peroxalate nanoparticles were capable of imaging hydrogen peroxide in the peritoneal cavity of mice, during an LPS-induced inflammatory response.
3:00 PM - HH11.2
Towards Improved Optical Imaging Probes: Fluorescent Core-Shell Silica Nanoparticles.
Erik Herz 1 , Andrew Burns 1 , Ulrich Wiesner 1
1 Mat. Sci. and Engineering, Cornell University, Ithaca, New York, United States
Show AbstractFluorescent colloidal silica nanoparticles (NPs) are increasingly recognized as a viable materials platform in the fields of biotechnology, sensing, security, optics and photonics. Specific silica particle architectures may provide increased brightness and improved dye stability against photobleaching, solvents, and aggressive environments over free dye. Furthermore, in comparison to semiconductor quantum dots (Q dots), dye doped silica NPs contain no heavy metals and have no fluorescence intermittence. Here we report on a particular class of silica NPs referred to as Cornell dots (C dots), which have a core-shell architecture. They are synthesized via a modified Stöber process in which the dye is covalently attached to the silica network (1, 2). With diameters of 20-30nm they have brightness levels comparable to those of same sized Q dots and exhibit improved photostability over free dye in solution (3). Such core-shell particles can be used, for example, for imaging of flow in biological systems, or with surface modifications, as tags for cellular imaging (4). Furthermore, sensor C dots have been prepared with multiple, chemically distinct dyes in different shells for pH and calcium sensing and have been employed for cellular metabolic status imaging (5). We will report on novel particle systems with emphasis on near-infrared emission wavelengths for bioimaging applications. Particle synthesis and characterization will be discussed.(1) Burns, A.; Ow, H.; Wiesner, U., Fluorescent core–shell silica nanoparticles: towards Lab on a Particle architectures for nanobiotechnology. Chemical Society Reviews 2006, 35, 1028-1042.(2) Ow, H.; Larson, D. R.; Srivastava, M.; Baird, B. A.; Webb, W. W.; Wiesner, U., Bright and Stable Core-Shell Fluorescent Silica Nanoparticles. Nano Lett. 2005, 5, (1), 113-117.(3) Larson, D. R.; Ow, H.; Vishwasrao, H. D.; Heikal, A. A.; Wiesner, U.; W.W.Webb, Silica Nanoparticle architecture determines radiative properties of encapsulated fluorophores. Chemistry of Materials 2008, in press.(4) Choi, J.; Burns, A.; Williams, R. M.; Zhou, Z.; Zipfel, W.; Wiesner, U.; Nikitin, A. Y., Core-Shell Silica Nanoparticles as Fluorescent Biological Labels for Nanomedicine Applications. Nature Medicine 2007, In preparation.(5) Burns, A.; Sengupta, P.; Zedayko, T.; Baird, B.; Wiesner, U., Core/Shell Fluorescent Silica Nanoparticles for Chemical Sensing: Towards Single-Particle Laboratories. Small 2006, 2, (6), 723-726.
3:15 PM - HH11.3
Quantum Dots for Tumor Targeted Drug Delivery and Cell Imaging.
Devesh Misra 1 , Qiang Yuan 1
1 Center for Structural and Functional Materials, University of Louisiana at Lafayette, Lafayette, Louisiana, United States
Show AbstractThe primary challenge in the treatment of cancer is early detection and targeting the anticancer drug specifically into and around tumors at concentrations that will decrease their growth and/or viability. An excellent vehicle to accomplish this objective is to develop a single system that is capable of targeting drug delivery and live cell imaging simultaneously to monitor time course of subcellular localization. We describe here the efficiency of a system that combines tumor targeting and cell imaging. The aim is to uniquely combine biodegradable chitosan (N-acetylglucosamine) for tumor-targeted drug delivery and semiconductor nanocrystal quantum dots (QDs) for non-invasive live cell imaging. In this regard, water soluble ZnO:Mn2+ QDs (3-6 nm) with long term fluorescence stability are synthesized by a chemical hydrolysis method and encapsulated with bio-functionalized chitosan. Chitosan enhances the stability of the QDs because of the hyrophilicity and cationic charge of chitosan. Additionally, the drug delivery function is effectively achieved by coating QDs with anticancer drug dispersed in folate conjugated chitosan.
3:30 PM - HH11.4
Genetically-Templated Magnetic Nanowires for Targeted Imaging.
Debadyuti Ghosh 1 , Youjin Lee 1 , Angela Belcher 1 2 , Kimberly Kelly 3
1 Materials Science and Engineering, Massachusettse Institute of Technology, Cambridge, Massachusetts, United States, 2 Biological Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States, 3 Center for Molecular Imaging Research, Massachusetts General Hospital and Harvard Medical School, Charlestown, Massachusetts, United States
Show AbstractIn an effort towards early tumor detection, various diagnostic probes, such as tumor marker-specific fluorescent and magnetic nanoparticles, have been developed. Nanoparticles detected using Magnetic resonance (MR) imaging is an attractive approach due to its non-invasiveness. Current work has focused on single functionalized nanoparticle systems, one example being cross-linked iron oxide nanoparticles (CLIO). Using the M13 virus as a scaffold, we can uniquely combine multiple nanoparticles with engineered cell-specific ligands. Using multimodal imaging, these nanoparticles can then be used to target tumors. Exploiting the multiple coat proteins on the M13 virus amenable for peptide display, we have engineered peptides that bind iron oxide nanoparticles (γ-Fe2O3 NPs) and that target prostate cancer-specific markers. We have synthesized monocrystalline , monodispersed γ-Fe2O3 NPs and attached them to the p8 protein coat of M13. The ~2700 copies of p8 allow for multivalent display of NPs and may increase sensitivity of detection for locating previously unnoticed lesions. We have displayed prostate cancer-specific targeting peptides on the p3 minor coat protein of M13. As a proof-of-concept, we have investigated targeting in vitro against a prostate cancer cell line. Using NMR spectrometry, we measured a decrease in T2 relaxation times and 50% improved iron uptake of targeted nanowires compared to the negative control. Future work involves investigating targeting in vivo. These virus-based targeted nanocrystal probes can be extended to other applications that can benefit from directed targeted imaging.
3:45 PM - HH11.5
Isobenzofuran-Based Near-Infrared Fluorophores for In Vivo Imaging
Scott Meek 1 , Brian Ferrara 2 , Scott Raymond 2 , Brian Bacskai 2 , Timothy Swager 1
1 Chemistry, MIT, Cambridge, Massachusetts, United States, 2 , Mass. General Hospital, Charlestown, Massachusetts, United States
Show Abstract4:00 PM - HH11: Imaging
BREAK
HH12: Cancer Targeting
Session Chairs
Wednesday PM, December 03, 2008
Room 310 (Hynes)
4:30 PM - HH12.1
Functionalized Magnetic Nanoparticles for Selective Targeting of Cells.
Wolfgang Tremel 1 , Mohammed Shukoor 1 , Filipe Natalio 2 , Thomas Schladt 1 , Stefan Fischer 3 , Maxim Terekhov 3 , Wolfgang Schreiber 3 , Hansjoerg Schild 4 , Heinz-Christoph Schroeder 2 , Werner Mueller 2
1 Institut für Anorganische Chemie und Analytische Chemie, Johannes Gutenberg-Universität, Mainz Germany, 2 Institut für Anorganische Chemie und Analytische Chemie, Johannes Gutenberg-Universität Mainz, Mainz Germany, 3 Institut für Physiologische Chemie, Johannes Gutenberg-Universität Mainz, Mainz Germany, 4 Institut für Radiologie, Johannes Gutenberg-Universität Mainz, Mainz Germany
Show Abstract4:45 PM - HH12.2
Intracellular Protein Kinase C-α Responsive Gene Regulation System for Tumor Specific Gene Therapy and Imaging.
Yoshiki Katayama 1 2 , Jeong-Hun Kang 1 , Riki Toita 1 , Tetsuro Tomiyama 1 , Daisuke Asai 3 , Hideki Nakashima 3 , Takeshi Mori 1 2 , Takuro Niidome 1 2
1 Applied Chemistry, Kyushu University, Fukuoka, Fukuoka, Japan, 2 Center for Future Chemistry, Kyushu University, Fukuoka, Fukuoka, Japan, 3 Virology, St. Marianna University School of Medicine, Kawasaki, Kanagawa, Japan
Show Abstract Present gene therapy has a serious problem with its target cell-specificity, since almost all the gene delivery methods have insufficient ability to specifically recognize the target disease cells and distinguish them from normal cells, especially in the same organ or tissue. Recently, we proposed a new concept for target cell-specific gene therapy (Drug or gene delivery responding to cellular signals: D-RECS) using new class of polymer-peptide conjugate. In this concept, an intracellular signal that is specifically and abnormally activated in the target disease cells is used as a trigger of transgene activation. Due to the cationic peptide side chains, the polymer forms tight complex with DNA and suppresses the gene transcription efficiently. On the other hand, if the complex is taken up by the target cell, where the target protein kinase is activated, the polymer is phosphorylated. Those events weaken the electrostatic interaction between the polymer and DNA. Thus, the transgene is activated for transcription only in the target cells.
We applied the concept to tumor specific gene expression using protein kinase C-α (PKCα) as the tumor specific intracellular signal. However, specific substrate peptide for the enzyme has not been reported. Thus, we designed more than 1700 kinds of peptide library and found FKKQGSFAKKK as a first PKCα-specific substrate after the screening them by using original peptide array system. The peptide was phosphorylated with lysates of various tumor tissues and cultured cancer cells, but not phosphorylated practically by lysates of other normal organs and tissues in mice. Therefore, D-RECS polymer grafted with the peptide was synthesized and evaluated its gene regulation ability by using some cancer cell lines and tumor bearing mice. We also synthesized a negative control polymer, in which phosphrylation site, serine residue, was replaced to alanine so that it is no longer phosphorylated by PKCα.
When the polymer/GFP encoding plasmid complex was incubated with cancer cell line, marked expression of such reporter gene was observed due to the high basal activity of PKCα. On the other hand, the expression level was much lower in the case of negative control polymer/plasmid complex. No expression was also obtained when the cell was pretreated with PKC inhibitor. Then the complex was applied to tumor bearing mice. When luciferase encoding reporter gene was injected as the polymer complex into tumor tissue, clear expression of luciferase was observed, but the injection of the complex into normal subcutaneous tissue did not give any expression. When therapeutic gene was used instead of reporter gene showed marked decrease of the tumor size.
We expected that the system would be useful as tumor specific gene therapy without side effect due to the gene expression in normal cell. The system is also expected as tumor imaging because the PKCα signaling is closely related with the activity of tumor cell proliferation.
5:00 PM - HH12.3
Single Walled Carbon Nanotubes: A New Vector for the Delivery of siRNA into Cancer Cells.
Paul Cherukuri 1 2 3 , Geoffrey Bartholomeuz 1 , Tonya Leeuw 3 , John Kingston 1 , Laurent Cognet 3 , Bruce Weisman 3 , Garth Powis 1
1 , The University of Texas MD Anderson Cancer Center, Houston, Texas, United States, 2 , Harvard University, Boston, Massachusetts, United States, 3 , Rice University, Houston, Texas, United States
Show AbstractWednesday, 12/3New Presentation Time/Paper NumberHH12.4 @ 4:15 PM to HH12.3 @ 4:00 PMSingle Walled Carbon Nanotubes: A New Vector for the Delivery of siRNA into Cancer Cells.Paul Cherukuri
5:15 PM - HH12.4
PEGylated Gold Nanoparticles Functionalized with Monoclonal Antibodies — New Biologically Targeted Labeling and Contrast Agents for Reflective Light Microscopy and X-ray Computed Tomography.
Wolfgang Eck 1 2 , Gary Craig 3 2 , Anthony Nicholson 4 , Michael Mason 3 2 , Peter Allen 5
1 Applied Physical Chemistry, University of Heidelberg, Heidelberg Germany, 2 Institute for Molecular Biophysics, The Jackson Laboratory, Bar Harbor, Maine, United States, 3 Department of Biological and Chemical Engineering, University of Maine, Orono, Maine, United States, 4 Technology Evaluation and Development, Physiology & in vivo Imaging, The Jackson Laboratory, Bar Harbor, Maine, United States, 5 Department of Surgery, Gastric and Mixed Tumor Service, Memorial Sloan Kettering Cancer Center, New York, New York, United States
Show AbstractWednesday, 12/3New Presentation Time/Paper NumberHH12.5 @ 4:30 PM to HH12.4 @ 4:15 PMPEGylated Gold Nanoparticles Functionalized with Monoclonal Antibodies — New Biologically Targeted Labeling and Contrast Agents for Reflective Light Microscopy and X-ray Computed Tomography. Wolfgang Eck
5:30 PM - HH12.5
Surface Engineering for in vivo Targeting Delivery of siRNA for Efficient Cancer Therapy.
Oleh Taratula 1 2 , Paul Kirkpatrick 1 , Ronak Savla 1 2 , Ipsit Pandya 1 , Tamara Minko 2 3 , Huixin He 1 3
1 Chemistry, Rutgers, the State University of New Jersey, Newark, New Jersey, United States, 2 Department of Pharmaceutics, Ernest Mario School of Pharmacy, Rutgers, the State University of New Jersey, Piscataway, New Jersey, United States, 3 , Cancer Institute of New Jersey, New Brunswick, New Jersey, United States
Show AbstractWednesday, 12/3New Presentation Time/Paper NumberHH12.6 @ 4:45 PM to HH12.5 @ 4:30 PMSurface Engineering for in vivo Targeting Delivery of siRNA for Efficient Cancer Therapy. Huixin He
HH13: Poster Session: Imaging and Targeted Delivery
Session Chairs
Thursday AM, December 04, 2008
Exhibition Hall D (Hynes)
9:00 PM - HH13.1
Highly Photostable Fluorescent Nanoparticles Based on Fullerene-silica Hybridization and Their Application to Bioimaging.
Jinyoung Jeong 1 , Nam Wong Song 2 , Bong Hyun Chung 1
1 Bionanotechnology research center, Korea Research Institute of Bioscience and Biotechnology, Daejeon Korea (the Republic of), 2 Nanobio Fusion Research Center, Division of Advanced Technology, Korea Research Institute of Standards and Science , Daejeon Korea (the Republic of)
Show AbstractRecently fluorescent carbon-based nanomaterials such as carbon nanoparticles and carbogenic quantum dots have been strongly considered to be alternative fluorescent probes in biotechnology due to their highly fluorescent property, possibility of multicolor coding, and simplicity of functionalization. In this study, we produced a new fluorescent fullerene-silica nanoparticle (FSNP) via a reverse-microemulsion method and utilized it as a bioimaging agent in living cells. FSNPs were synthesized as homogenous spheres of ~ 60 nm in diameter and well-dispersed in aqueous solution. Although fullerene has extremely low fluorescence quantum yield (1 x 10-4), the FSNP showed ~ 35 times higher quantum yield and ~ 600 times higher absorbance at 350 nm than fullerene. As a result FSNPs exhibit ~ 21,000 times higher photoluminescence in brightness than C60 molecules. Furthermore, it exhibited ~ 10 times higher photostability compared to the conventional fluorescent dye of Alexa488® which was revealed by single dot fluorescence analysis. The FSNPs incorporated in macrophage cells (RAW 264.7) were clearly visualized by fluorescence microscopy in a wide excitation range showing highest brightness at 340 nm excitation. While the fluorescence of incorporated Alexa488® in the cell was completely vanished, the emission intensity of FSNPs in the cell remained to be ~ 50 % of the initial value after 10 min continuous irradiation of 488 nm light. The new synthetic FSNP can be a promising fluorescent probe for bioimaging analysis based on its brightness and high photostability.
9:00 PM - HH13.11
A GEPI- Huntingtin Construct forReal Time Monitoring of Huntington Fibril Elongation Kinetics.
Sibel Cetinel 1 , Urartu Seker 1 , Candan Tamerler 1 2 , Paul Muchowski 3 4 , Mehmet Sarikaya 1 2
1 Molecular Biology and Genetics, Istanbul Technical University, Istanbul Turkey, 2 Genetically Engineered Materials Science and Engineering Center, Materials Science & Engineering, University of Washington, Seattle, Washington, United States, 3 Gladstone Institute of Neurological Disease, University of California, San Francisco, California, United States, 4 Biochemistry and Biophysics, University of California, San Francisco, California, United States
Show Abstract9:00 PM - HH13.12
Quantum Dot/Gold Nanoparticle-based Protein Kinase Assays.
James Ghadiali 1 , Molly Stevens 1
1 Materials, Imperial College, London, London United Kingdom
Show Abstract9:00 PM - HH13.13
Novel Optically-Activated Liposome Release via Gold Nanoshells.
Guohui Wu 1 , Alexander Mikhailovsky 2 , Htet Khant 3 , Caroline Fu 3 , Wah Chiu 3 , Joseph Zasadzinski 1
1 Chemical Engineering, University of California, Santa Barbara, California, United States, 2 Department of Chemistry, University of California, Santa Barbara, California, United States, 3 Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas, United States
Show Abstract9:00 PM - HH13.14
Delivery of Doxorubicin to Solid Tumors using Thermosensitive Liposomes.
Elizaveta Tazina 1 , Alevtina Polozkova 1 , Elena Ignatieva 1 , Olga Orlova 1 , Valeria Mescherikova 1 , Adolf Wainson 1 , Natalia Oborotova 1 , Anatoliy Baryshnikov 1
1 Research Institute of Experimental Diagnostics and Therapy of Tumors, N.N. Blokhin Russian Cancer Research Center of RAMS, Moscow Russian Federation
Show Abstract9:00 PM - HH13.15
Precise Control of Variable Sized Ligand Clusters for Multivalent Interactions using Linear Dendritic Copolymers.
Zhiyong Poon 1 , Paula Hammond 1
1 , mit, Cambridge, Massachusetts, United States
Show Abstract9:00 PM - HH13.16
Functionalized Quantum Dot – Liposome Hybrids as Multi-Modal Nanoparticles for Cancer.
Wafa' Al-Jamal 1 , Khuloud Al-Jamal 1 , Kostas Kostarelos 1
1 , The School of Pharmacy, London United Kingdom
Show Abstract9:00 PM - HH13.17
Multifunctional Uniform Magnetite-Core/Mesoporous-Silica-Shell Nanoparticles for Simultaneous Magnetic Resonance and Fluorescence Imaging, and Drug Delivery.
Jaeyun Kim 1 , Hoe Suk Kim 2 , Nohyun Lee 1 , Taeho Kim 1 , Hyoungsu Kim 2 , Taekyung Yu 1 , In Chan Song 2 , Woo Kyung Moon 2 , Taeghwan Hyeon 1
1 National Creative Research Initiative Center for Oxide Nanocrystalline Materials and School of Chemical and Biological Engineering, Seoul National University, Seoul Korea (the Republic of), 2 Diagnostic Radiology, Seoul National University Hospital, and the Institute of Radiation Medicine, Medical Research Center,, Seoul National University, Seoul Korea (the Republic of)
Show AbstractMultifunctional nanostructured materials have been intensively studied for their applications to multimodal imaging and simultaneous diagnosis and therapy. Here we report on the fabrication of uniform-sized core/shell nanoparticles composed of monodisperse superparamagnetic nanocrystal core and uniform mesoporous silica shell. The core/shell nanoparticles were synthesized from silica sol-gel reaction in the presence of the uniform hydrophobic nanocrystal seeds. Various nanocrystals with different materials including Fe3O4, MnO, and FeOOH, and different shapes can be coated with uniform mesoporous silica shells, demonstrating a general applicability of the current process. In addition, fluorescent dyes can be easily anchored into the silica walls of the core/shell nanoparticles, and the functionalization with PEG increased colloidal stability of the nanoparticles significantly in phosphate buffered solution. The core/shell nanoparticles exhibit many important characteristics for biomedical applications including superparamagnetism for T2 magnetic resonance imaging (MRI), fluorescence for optical imaging, and uniform mesopores for drug delivery. We demonstrated simultaneous T2 MR and fluorescent imaging, and drug delivery using the multifunctional core/shell nanoparticles.
9:00 PM - HH13.18
Stabilization and Functionalization of Multilayered Capsules using Thiol–ene Click Chemistry.
Luke Connal 1 , Frank Caruso 1 , Cameron Kinnane 1
1 Chemical and Biomolecular Engineering, the University of Melbourne, Melbourne, Victoria, Australia
Show Abstract9:00 PM - HH13.2
Triggered Binding of Targeted Lipid Vesicles to Cancer Cells Mediated by Formation of pH-sensitive Heterogeneous Lipid Domains.
Shrirang Karve 1 , Gautam Bajagur Kempegowda 1 , Stavroula Sofou 1
1 Chemical and Biological Engineering, Polytechnic University, Brooklyn, New York, United States
Show AbstractFor targeted drug delivery to metastatic tumors with developed vasculature, preferential accumulation and retention of the drug carrier in the tumor interstitium depends primarily on the carrier size. Only after the drug carriers are localized in the tumor interstitium, are cancer-targeting ligands necessary to enhance adhesion of the carriers to cancer cells, and to mediate their cellular internalization. At all other times, during circulation in the blood stream, ‘decoration’ of the drug carrier surface with tumor-seeking ligands will most certainly activate non-desirable interactions with the immune and reticuloendothelial systems resulting in accumulation of drug carriers in healthy organs. At these sites the carriers will eventually release their therapeutic contents killing healthy cells and increasing toxicity.With the above rationale in mind, we designed lipid vesicles as drug carriers with cancer-targeting ligands on their surface and membrane-tunable properties to enable triggered binding. We designed vesicles with membranes that phase-separate as a response to pH and form lipid-heterogeneities resembling reversible ‘(nano)patterns’ on the vesicle membrane: we use this mechanism to selectively expose binding ligands and, therefore, to control binding of vesicles.Heterogeneous lipid membranes tuned by pH were evaluated at 37oC in the form of PEGylated/biotinylated vesicles composed of lipid pairs with two types of headgroups. One lipid type was chosen to have the titratable moiety phosphatidylserine on its headgroup, and the other lipid type to have a phosphatidylcholine headgroup. Upon phase separation triggered by lower pH values, PEGylated lipids and biotinylated lipids are designed to preferentially partition in different separated lipid domains, exposing the binding ligands and allowing for binding to the target. The effect of pH on formation of lipid heterogeneities and on the extent of specific binding was studied on biotinylated vesicles composed of different fractions of PEGylated lipids. These vesicles exhibit low binding at physiologic pH and pronounced binding at the slightly acidic pH values of 6.7-6.5 of the tumor interstitium. Our results suggest the potential of these vesicles for targeted delivery to vascularized tumors. In addition, with these vesicles it could be possible to increase penetration into the tumor by overcoming the “binding site barrier” effect.
9:00 PM - HH13.3
Targeted In-vitro Delivery of a Chemotherapeutic Agent to Human Hepatocellular Carcinoma via a Bacteriophage Carrier.
Mekensey Buley 1 , Carlee Ashley 2 , David Peabody 3 , C. Jeffrey Brinker 2 4
1 Chemical, Biological, and Materials Engineering, University of Oklahoma, Norman, Oklahoma, United States, 2 Chemical Engineering, University of New Mexico, Albuquerque, New Mexico, United States, 3 Molecular Genetics and Microbiology, University of New Mexico, Albuquerque, New Mexico, United States, 4 Self-Assembled Materials, Sandia National Laboratories, Albuquerque, New Mexico, United States
Show AbstractThe concentration of most chemotherapeutic agents that accumulates at tumor sites is less than 10% of the total administered dose, leading to toxic side effects. Several approaches have been developed to improve the selective toxicity of chemotherapeutic agents and include encapsulating drugs in polymer or lipid-based delivery systems and conjugating drugs to monoclonal antibodies or peptide ligands that bind to receptors uniquely expressed or overexpressed by the cancer cell. Passive and active drug targeting can result in a several-fold increase in drug concentration at the tumor site relative to concentrations obtained with free drug. Bacteriophages are ideal drug carriers since their size (10’s to 100’s of nanometers) enables rapid cellular uptake and the inner and outer surfaces of their protein capsids can be readily modified with targeting peptides and various drugs. Furthermore, development of a complex bacteriophage-based random peptide library enables both identification of targeting peptides and production of bacteriophage drug carriers in a single, rapid, cost-effective process. To this end, we have employed a heterobifunctional crosslinker to chemically conjugate a synthetic peptide (SP94, which has the N-terminus to C-terminus amino acid sequence SFSIIHTPILPLGGC) previously identified to have a high affinity for human hepatocellular carcinoma to surface lysine residues present in the capsid of MS2, a 28-nm RNA bacteriophage of Escherichia coli. We then conjugated a chemotherapeutic agent, doxorubicin, to the inner surface of MS2 using a NHS ester-maleimide reagent to link a primary amine moiety present in doxorubicin to RNA modified with a 3’ or 5’ sulfhydryl group; MS2 coat protein binds to RNA with high affinity and spontaneously encapsidates RNA-drug complexes. We have fluorescently labeled the MS2 capsid with Alexa Fluor 555 carboxylic acid succinimidyl ester and the RNA-doxorubicin conjugate with an Alexa Fluor 647 nucleic acid stain and used fluorescence-activated cell sorting to confirm that MS2 capsids bearing the SP94 targeting peptide bind to human hepatocellular carcinoma Hep3B cells with high affinity at various concentrations, while demonstrating a low affinity for a control human hepatocyte cell line. We have also employed confocal microscopy to demonstrate that SP94-MS2 capsid conjugates are rapidly internalized by Hep3B cells via receptor-mediated endocytosis. We are testing the in-vitro cytotoxicity of the SP94-MS2 doxorubicin delivery system in hepatocellular carcinoma tissue culture using a LIVE/DEAD viability assay. The cytotoxicity of targeted MS2-doxorubicin conjugates will be compared to that of targeted MS2, MS2 bearing a control peptide (N-to-C amino acid sequence FPWFPLPSPYGNGGC), MS2 bearing the control peptide loaded with doxorubicin, wild-type MS2, wild-type MS2 loaded with doxorubicin, and free doxorubicin.
9:00 PM - HH13.4
Covalently Linking Quantum Dots to Cellular Proteins using HaloTag.
Justin Galloway 1 3 , Meghdad Rahdar 2 3 , Kwan-Hyi Lee 1 3 , Jeaho Park 1 3 , Taegweon Lee 1 3 , Peter Devreotes 2 3 , Peter Searson 1 3
1 Material Science and Engineering, Johns Hopkins University, Baltimore, Maryland, United States, 3 The Institute for NanoBioTechnology , Johns Hopkins University, Baltimore, Maryland, United States, 2 The Department of Cell Biology, Johns Hopkins University School of Medicine, Baltimore, Maryland, United States
Show Abstract9:00 PM - HH13.6
Highly Luminescent Silica Beads Dispersing CdTe Nanocrystals Prepared by a Reverse Micelle Method.
Norio Murase 1 , Ping Yang 1 , Masanori Ando 1
1 , National Institute of Advanced Industrial Science & Technology, Ikeda, Osaka, Japan
Show AbstractHighly luminescent silica beads (30 nm–2 μm) incorporating CdTe nanocrystals (NCs) coated by thioglycolic acid (TGA) were prepared via a modified Stöber synthesis (Step 1) and a subsequent reverse micelle route (Step 2). In Step 1, the silica molecules originated from tetraethoxysilane are deposited on the surface of the NCs. The thickness of the silica layer was estimated to be 0.6 nm. During this coating, TGA molecules are not removed from the surface. These coated NCs were incorporated into silica beads in Step 2 by using inversed micelles consisting of Igepal CO-520 and cyclohexane. Chemical analysis told that a red-emitting silica bead of 30 nm in diameter thus prepared encapsulated roughly 14 CdTe QDs. These glass beads (30–40 nm in diameter) retained the initial photoluminescence (PL) efficiencies of the colloidal NCs (27 and 65% for the green- and red-emitting beads, respectively). The protection of NCs by a silica layer at Step 1, together with the short total reaction time, is the main reason for the retention of the initial PL efficiency. The size of the glass beads can be easily controlled over the wide range by adjusting the injection speed of aqueous solution and the ratio of chemicals used for the reverse micelle preparation. Since the original PL efficiency was maintained in the beads and is the highest ever reported for NC-containing silica beads, the method presented here is of significant importance for applications to biological probes.
9:00 PM - HH13.7
Supramolecularly Wrapped Polysaccharides: Versatile Molecular Shuttles for Nanoclinics.
Giorgio Macchi 1 2 , Francesco Meinardi 1 2 , Riccardo Tubino 1 2 , Patrizio Salice 1 3 , Silvia Versari 4 , Alessandro Villa 4 , Silvia Bradamante 4 , Luca Beverina 1 3 , Giorgio Pagani 1 3
1 Scienza dei Materiali, Università di Milano Bicocca, Milano Italy, 2 , INFM, Milano Italy, 3 , INSTM, Milano Italy, 4 CNR-ISTM, Institute of Molecular Science and Technology, Milano Italy
Show AbstractSinglet oxygen sensitization by organic molecules is a topic of major interest in the development of efficient photodynamic therapy (PDT) agents. Among the large number of known photosensitizers, squaraine dyes possess an exceedingly strong one- and two photon absorption enabling for their use at the wavelengths relevant for clinical applications (644 nm and 806 nm, respectively). A challenge that occurs when dealing with lipophilic photosensitizers is the way they are solubilized and specifically delivered to the biological target. In order to overcome this problem, we have already demonstrated the feasibility of exploiting amylose helical form in aqueous environment as an efficient nanocapsule to incorporate highly hydrophobic moieties. Within this line of thoughts, we designed and synthesized inclusion compounds of non-symmetrical squaraine dyes with both oligo- (cyclodextrins) and polysaccharides (amylose). The obtained materials were characterized by means of continuous-wave and time-resolved UV-vis-NIR spectroscopy. Through optical absorption and photoluminescence spectroscopy in vivo, the estimation of singlet oxygen generation efficiencies, intrinsic dark toxicity, and subcellular localization we obtained encouraging results about the delivery capabilities of these water-soluble squaraine-based inclusion compounds, opening the way for their use in PDT applications.
9:00 PM - HH13.8
In Vitro Study of Cancer Cells and Therapeutic Changes Due to Interactions with Drug Delivery Material Systems.
Krystle Laja 1 , Michelle Brusatori 1 , Joseph Smolinski 1 , Bonnie Sloane 2 , Gregory Auner 1
1 Electrical and Computer Engineering, Wayne State University, Detroit, Michigan, United States, 2 Pharmacology, Wayne State University, Detroit, Michigan, United States
Show AbstractWhile the ability to detect cancer cells is of great clinical significance, the ability to track the effectiveness of treatment is of equal importance. To evaluate cell response to cancer treatment, we constructed a live cell imaging system that provides time elapsed photography combined with multi-spectral Raman for live cell imaging or morphology and biomolecular analysis, respectively. The live cell imaging Raman system provides molecular information about the cell as well as visual observation over a period of up to several months. Our use of a multi-spectral Raman system will provide greater information than possible in previous studies that utilize a single wavelength. The use of multi-wavelength Raman provides information at the molecular level normally covered up by background such as fluorescence and other interfering signals. We have used this system to investigate the effect of breast cancer, three dimensional cultures, and their interaction with a drug delivery material. A systematic study of the effect of the drug delivery material on the intra and inter cellular composition and modification will be presented. This information will be of great use in the understanding of drug therapy on cancer cells down to the molecular level. Cellular-material interactions were also investigated post treatment using atomic force microscopy and x-ray photoemission spectroscopy to elicit cellular-material interface effects.
9:00 PM - HH13.9
Construction of Magnetic-fluorescent Nanocomposites for Cellular Engineering and Molecular Imaging: Different Synthesis Approaches.
Gang Ruan 1 , Shuang Deng 1 , Dhananjay Thakur 2 , Jessica Winter 1 2
1 Chemical, Biomolecular and Biomedical Engineering, the Ohio State University, Columbus, Ohio, United States, 2 Biophysics Program, the Ohio State University, Columbus, Ohio, United States
Show AbstractThe applications of superparamagnetic iron oxide nanoparticles (SPIONs) and fluorescent quantum dots (QDs) in biomedicine have been extensively demonstrated. For example, quantum dots have been used for single molecule tracking, cell labeling, biosensing, and fluorescence resonance energy transfer (FRET). Similarly, SPIONs have been used for MRI imaging and cell separation. Here we describe our efforts in assembling hybrid structures of these two types of nanoparticles for bi-functionalities in a variety of biomedical applications. We first synthesized SPIONs and QDs by thermal decomposition or microemulsion techniques. We then explored different synthesis approaches of the nanocomposites, including sequential crystallization, water-based conjugation, and micelle co-encapsulation. It was found that the different synthesis methods resulted in different crystal structures, and thereby different magnetic and fluorescent properties. Nanocomposites formed by micelle co-encapsulation were found to possess the best overall qualities. We are further investigating the effects of micelle formulations, and exploring a number of applications of these nanocomposites for basic biomedical research and clinical diagnosis, imaging and therapy. We believe that forming nanocomposites such as the SPION-QDs as described above will greatly expand the application of nanomaterials in biology.
9:00 PM - HH13: TRGTDEL
HH13.5 Transferred to HH11.5
Show Abstract