10:15 AM - SM5.4.03
Azobenzene-Modified Silk Gels for Light-Induced Surface Patterning
Michael Landry 1,Matthew Applegate 2,Siran Wang 2,Mark Cronin-Golomb 2,Christopher Barrett 1,Fiorenzo Omenetto 2,David Kaplan 2
1 Chemistry McGill University Montreal Canada,2 Biomedical Engineering Tufts University Medford United StatesShow Abstract
Silk fibroin from Bombyx mori silkworms is used in diverse applications in materials science due to its high availability, low cost, and rich polymer chemistry. Although silk can be processed into various material classes that are suitable for biological material applications, such as tissue engineering,1 further enhancement of its properties can be achieved through facile chemical modifications of the amino acid side chains. Such modifications greatly diversify the properties of silk in a minimal number of synthetic steps.
One method to retain the biocompatibility of silk, while enhancing its optical properties is functionalization with azobenzene, yielding a material called AzoSilk.2 Tyrosine, an amino acid contained in silk can be converted into azobenzene via traditional diazonium coupling under aqueous conditions. In this study, families of AzoSilk materials have been synthesized by varying the structure of aniline used in the reaction. Subsequently, Azosilk solutions are plated onto plasma-treated petri dishes, and allowed to dry slowly over 5 days. This produced a family of light-responsive water-resistant films for study that can be swelled with water.
Upon examining re-hydrated AzoSilk films under a two-photon microscope, we discovered the appearance of persistent fluorescent patterns within the irradiated areas of the films. The written patterns can be easily visualized by observing the fluorescence emitted at 550 nm, excited by 800 nm. In this microlithographic process, out-of-plane expansion of the film causes micrometre-sized blisters to form near the surface. Micro-blisters were characterized using underwater AFM, and exhibited a 10-fold decrease in modulus. The induced radius of curvature associated with blister formation, together with significant photo-softening are expected to be valuable material characteristics for guided cell growth.3
In order to assess cytotoxicity of hydrated AzoSilk films, they were plated with Chinese hamster ovary cells, and tested with a standard live/dead assay over 3 hours. Sodium sulfanilate-based AzoSilk exhibited the best cell viability(90%+ alive) due to its highly charged surface. Having identified the best surface for cell viability, we currently study the effect of this surface on chick embryo neurons. We notice that surfaces with high acidity provide the best surfaces, due to their high positive charge and thus good adhesion.
To summarize, photo-induced patterning in AzoSilk materials provides optically tunable, biocompatible surfaces that can be photo-softened by laser light irradiation. The patterning of Azosilk films can be controlled through the two-photon process and yields promising surfaces to guide cell growth by providing a tunable radius of curvature of photo-induced features.
1. Kaplan, D.L et al. Nat. Prot. 6, 2011, 1612.
2. Murphy, A.R. et al. Biomaterials, 29, 2008, 2829.
3. Lucido, A.L. et al J. Neuro. 29, 2009, 12466.
12:00 PM - SM5.4.08
Biological Evaluation of Hydroxyapatite/Collagen Paste with (3-Glycidoxypropyl)trimethoxysilane
Taira Sato 1,Yuki Shirosaki 2,Masaki Nagaya 3,Yoshinori Asano 1,Kazuaki Nakano 1,Hiroshi Nagashima 3,Mamoru Aizawa 1,Masanori Kikuchi 4
1 Meiji University Kawasaki Japan,2 Kyushu Institute of Technology Kikakyushu Japan3 Meiji University International Institute for Bio-Resource Research Kawasaki Japan1 Meiji University Kawasaki Japan,3 Meiji University International Institute for Bio-Resource Research Kawasaki Japan4 National Institute for Materials Science Tsukuba JapanShow Abstract
Self-setting bone pastes can be utilized for minimally invasive surgery and can fit to the complicated shape of bone defects easily; however, presently practically available pastes are hardened via transformation of calcium phosphates into hydroxyapatite which has weak mechanical strength and no or low biodegradability. Therefore, surgeons desire biodegradable/bioresorbable self-setting bone paste. A hydroxyapatite/collagen bone like nanocomposite (HAp/Col) porous body has been clinically applied in Japan as a bioresrobable bone filler, because the HAp/Col is incorporated into bone remodeling process. A self-setting HAp/Col paste could be a good candidate for the next generation bone void filler. In this study, 1.0 or 10 % aqueous solution in volume of (3-glycidoxypropyl)trimethoxysilane (GPTMS), which works as a cross-linker of collagen via amino groups and forms siloxane network by self-condensing after hydrolysis, was mixed with the HAp/Col powder to prepare the HAp/Col biodegradable self-setting pastes, and their mechanical and biological properties were investigated.
The HAp/Col at the hydroxyapatite and collagen mass ratio of 80:20 was synthesized by the simultaneous titration method. The HAp/Col powder, a powder phase of HAp/Col self-setting bone pastes, was prepared by a uniaxial compacting dehydration, freeze-drying, crushing and classifying to 100 μm or less in particle size. Liquid phase of the pastes was 1.0 or 10 % GPTMS aqueous solution 1 hour after mixing, to allow hydrolysis of GPTMS. The powder/liquid (P/L) ratio of the pastes was 1.00 g/cm3, which would be optimal condition for the paste anti-decay. The viscosity of the HAp/Col pastes fabricated was measured by according to follows, a total 2 kg of glass plate and weight were placed on 0.1 cm3 of the cylindrical paste 10 minutes after mixing started, and the spread area was measured at 10 minutes after placing the weight as its viscosity. Biological reactions of the pastes were investigated by the implantation in porcine tibia. Cylindrical defects of 4.0 mm in diameter were formed by surgical drill. The pastes, prepared on site, were then injected into the defects. After 12 weeks, histological sections of the paste and surrounding tissues were observed to evaluate its biodegradability and biocompatibility.
Viscosity of the paste with 10 % GPTMS solution was larger than that 1.0 %. Rapid siloxane network formation in the paste prepared with 10 % GPTMS than 1.0 % would cause increasing in solution viscosity. The results of histological analysis for the HAp/Col-GPTMS pastes will be presented on a podium.
3:00 PM - SM5.5.02
Corrosion Behavior of Biodegradable Poly(Succinimide-Citramide) Coating on AZ31 Magnesium Alloys
Yu-Ren Chu 1,Chao-Sung Lin 1
1 Department of Materials Science and Engineering, National Taiwan University Taipei Taiwan,Show Abstract
In recent years, the application of magnesium in biomedical use has been getting more and more attention. Regarded as a promising bio-compatible material, magnesium has both good bio-degradability and sufficient mechanical properties, which allow the applications in not only drug delivery vehicles, but also implants including temporary anchorage devices and artificial joints. However, when serving as an implant, magnesium has a highly active chemical property and tends to suffer a high rate corrosion that is generally accompanied with observable hydrogen evolution. In order to control the degradation rate to a proper value, surface modification is thus indispensable.
In previous studies about magnesium in biomedical applications, many different kinds of surface modification processes have been investigated, including magnesium oxide coatings formed using micro-arc oxidation (MAO) and hydroxyapatite (HA) coatings deposited through electrodeposition or conversion coating process. Nonetheless, these coatings have either no biological activity or comparable biodegradability, and may be not the best solution for biodegradable magnesium alloys. Amongst various potential replacements, one candidate standing out is polyaspartic acid (PAS). PAS is a biodegradable polyaminoacid used in many different applications including corrosion inhibition, and the its effect on both HA deposition and dentin remineralization has also been disclosed in the past few years. To synthesis PAS, the key precursor polysuccinimide (PSI) is required, yet the preparation is usually complicated and expensive.
In 2012, Jiang et al. presented a new approach to produce a copolymer called poly(succinimide-co-citramide) (PSICA), which has the molecular structure of PSI, through a solvent-free condensation reaction between hexamethylene (HDMA) and citrate ester. In this present study, the same approach was used to form a PSICA top coating on AZ31 magnesium alloys with or without a citrate intermediate layer. The corrosion properties of polymer-coated AZ31 in both chloride-containing solution and simulated body fluid were investigated using electrochemical impedance spectroscopy (EIS). As shown in the results, the PSICA coating elevated the total impedance, which indicates a slower corrosion rate and decelerated hydrogen evolution. Besides, as the immersion time increased, the change in impedance of coated AZ31 was smaller than that of untreated AZ31, suggesting that the degradation of PSICA coating itself can help maintaining the degradation of magnesium coated underneath in a relatively stable rate.
1. G. Song, Corros. Sci., 49(4), 1696 (2007)
2. S.Z. Xu, X.Y. Yang, X.Y. Chen, X.J. Lin, L. Zhang, G.J. Yang, C.Y. Gao, and Z.R. Gou, Biomed. Mater., 6, 035002 (2011)
3. M. Jiang, W. Chen, P. Fang, S.L. Chen, J.X. Bai, Y.F. Huang, M.W. Han, P. Lu, and J. Dong, J. Polym. Sci., Part A: Polym. Chem, 50, 3819 (2012)
3:45 PM - SM5.5.05
Biodegradable Metal-Corrosion Induced Formation of Reactive-Oxygen-Species (ROS) for Tissue Engineering
Jimin Park 1,Kyoungsu Kim 1,Hyung-Seop Han 1,In-Dong Jun 1,Jin-Kyung Jeon 1,Hojeong Jeon 1,Hyun-Kwang Seok 1,Myoung-Ryul Ok 1,Yu-Chan Kim 1
1 Korea Institute of Science and Technology Seoul Korea (the Republic of),Show Abstract
Inspired by their unique biodegradable properties, magnesium and their alloys have received extensive attentions as a candidate material for bone-fixation devices and stents. However, electrons and hydrogen gas generated from the corrosion of such metals have an adverse effect on human body, thus significantly limiting their practical usage in clinical setting. In this study, we developed a novel strategy that utilizes these electrons for the generation of the reactive-oxygen-species (ROS), which is one of the pivotal signal molecules in various physiological events.
In the first section, we presented a new type of electrochemical system using biodegradable metals. Similar to the chemical reaction in the primary battery, electrons generated from the corrosion of the biodegradable magnesium anode were transferred to the nanostructured titanium cathode. The transferred electrons were utilized for converting oxygen molecules near the cathode to ROS molecules by oxygen-reduction-reaction (ORR). Combining spectroscopic and electrochemical analyses, we found that hydrogen peroxide (H2O2) can be spontaneously generated by the corrosion of the metal. By precisely tuning the material parameters and discharging time, we could control the released amount of H2O2 from 1 uM to 100 uM. Interestingly, the controlled release of H2O2 (~ 10 uM ) from our electrochemical system apparently enhanced in-vitro angiogenesis, even in the condition where no growth factor exists. It is noteworthy that our system can support the angiogenesis, which is one of the core prerequisites in tissue regenerative engineering, comparable to positive results with growth factors. Finally, by combining magnesium anode in the titanium bone-fixation devices, we developed integrated type bone-fixation devices that can support angiogenesis.
In the following section, we applied our electrochemical system for stent application. Because the re-coarctation have been one of the most imminent problems in stent-applications, previous efforts have been made on increasing the proliferation of HUVECs and simultaneously decreasing that of smooth muscle cells (SMCs). Combining a small amount of biodegradable metals on the metal stent, we could precisely tune the released amount of H2O2, and finally we were successful at finding the optimum H2O2 concentration where the proliferation of HUECS increased, while that of smooth muscle cells (SMC) decreased. Additionally, long-term fatigue tests showed that our metal-based system is superior to conventional polymer-metal hybrid one.
Ultimately, we applied corrosion of biocompatible metals to generate ROS near the implantable devices. Conventional devices could be functionalized to improve tissue engineering aspect of it by utilizing our electrochemical system. We believe that our approach can be further extended to versatile biodegradable metal platforms.
4:45 PM - SM5.6.02
Engineering Bio-Interfaces with Phase-Reversion Induced Nanostructured Materials: Self-Assembly of Protein at Bio-Interfaces
Krishna Nune 1,Devesh Misra 1,M.C. Somani 2
1 Department of Metallurgical, Materials, and Biomedical Engineering University of Texas at El Paso El Paso United States,2 Mechanical Engineering University of Oulu Oulu FinlandShow Abstract
Metallic biomedical devices with nanometer-sized grains (NGs) provide surfaces that are different from their coarse-grained (CG) (tens of micrometer) counterparts in terms of increased fraction of grain boundaries (NG > 50%; CG
5:00 PM - SM5.6.03
MiR-29b Nanocapsules Functionalizing Titanium Alloy to Stimulate the Bone Regeneration
Yubin Meng 1,Xue Li 2,Zhaoyang Li 1,Jin Zhao 1,Xubo Yuan 1,Zhenduo Cui 1,Xianjin Yang 1
1 School of Materials Science amp; Engineering Tianjin University Tianjin China,2 School of Laboratory Medicine Tianjin Medical University Tianjin ChinaShow Abstract
Titanium and its alloys have been widely used over the past three decades as implants for fixing bone defects. Surface modification is often performed to improve their biological and chemical properties. Recently, the delivery of miRNA with osteogenic differentiation capability has been recognized to have great potential for bone regeneration. Here, we modified the titanium surface to improve its osteogenic bioactivation using a nanocapsule-based miR-29b (n-miR-29b) coating. After internalization in the nanocapsules and mixture with biocompatible Carboxymethyl chitosan (CMCS), the n-miR-29b coating was used as a tool for the intracellular delivery of miR-29b. The effect of this coating on osteogenic differentiation was evaluated in vitro using human umbilical cord mesenchymal stem cells (hUMSCs). The upregulated expression of the osteogenic markers and the highest amount of calcium nodule formation in hUMSCs treated with the miR-29b nanocapsules confirmed that the n-miR-29b coating effectively induced osteogenesis.
To study the ability of the miRNA delivery system to enhance bone repair, the tibial defect model was generated in Sprague-Dawley (SD) rats. A 3-mm diameter round cortical and medullary defect was created and then these defects were filled with titanium rods. The histomorphometric analysis showed that the bone regeneration ratio for n-miR-29b coated titanium was much higher than that for the pure titanium scaffold. This confirmed that the miR-29b incorporated into the coating promoted the formation of bone tissue on the titanium implants without inducing any obvious inflammation. The immunohistochemistry results indicated that miR-29b targets HDAC-4, which is involved in inhibiting osteoblast differentiation, and promotes the expression of the osteogenic markers RUNX-2 and OCN. More importantly, the in vivo bone defect experiment showed that miR-29b was successfully transfected in vivo via the nanocapsules and that miR-29b promoted the bone formation ability of titanium.
In summary, we used nanocapsules with high transfection efficiency to coat the osteogenic-related gene, miR-29b, on the surface of titanium to enable its osteogenic bioactivation. The functional coating system enhanced not only the osteogenic differentiation ability in vitro but also the bone regeneration ability of the titanium alloy in vivo, which is essential for potential clinical applications in bone regeneration therapy.
5:15 PM - SM5.6.04
Time Dependent Changes in Strength and Micro-Hardness of Bioactive Cements
Steven Jefferies 1,Jasi Almutairi 1,Holly Gray 1
1 Kornberg School of Dentistry/Temple University Philadelphia United States,Show Abstract
Calcium silicate and calcium aluminate cements display surface bioactivity: The ability to form surface apatite when immersed in simulated physiologic solution containing inorganic phosphate. The objective of this study was to compare time dependent bulk strength and micro-hardness of several bioactive cement compositions as compared to that of non-bioactive cement, a conventional glass ionomer. Materials & Methods: Compressive strength (MPa) of both bioactive and non-bioactive dental cements were evaluated for extended time-points up to 1 year using the method for ISO 9917-1. Three bioactive materials [Ceramir Crown & Bridge Cement (CCB), Mineral Trioxide Aggregate (MTA), Biodentine (BD)], and a glass ionomer cement, Fuji I luting cement (F1), were utilized in this study. Microhardness specimens were prepared in a standard cylindrical mold 1.5 mm in height and 12.0 mm in diameter and stored in Phosphate-Buffered-Saline (PBS) at 37 degrees C. prior to testing to determine Vickers micro-hardness in a CSM micro-indentation testing device. Microhardness specimens were tested at 24 hours and 2 months and 11 + 1 month’s incubation time. Results: The compressive strength of the calcium silicate cement decreased significantly over extended time-periods in PBS, while the other bioactive and control materials displayed stable strength properties. The bioactive materials displayed significant differences in Vickers hardness as a function of storage time as compared the Vickers hardness values over the similar timeframe for the control material, the glass ionomer material Fuji 1. The control glass ionomer cement did not displayed significant changes in Vickers hardness after prolonged liquid storage. The experimental bioactive materials both demonstrated long-term trends with significant increases (CCB) and decreases (Biodentine) in Vickers hardness after storage in the simulated body fluid (PBS). The mean Vickers hardness of the calcium aluminate/glass ionomer (CCB) material was significantly greater than the mean Vickers hardness values for the other three materials tested at all time-points evaluated. Conclusions: The bioactive calcium silicate cement experienced a significant decrease in compressive strength over extended storage times in a simulated physiologic solution (PBS). Unlike non-bioactive glass ionomer cement, both the calcium silicate and calcium aluminate/glass ionomer cements displayed significant changes in surface micro-hardness after prolonged storage in a simulated body fluid (PBS). The calcium silicate cement had a significant reduction in surface micro-hardness over the testing period. The calcium aluminate/glass ionomer cement displayed a significant increase in surface micro-hardness over that same time period. The formation of and changes in the bioactive surface layers formed on these materials may account for changes in the micro-hardness of these bioactive materials.
SM5.7: Poster Session
Friday AM, April 01, 2016
Sheraton, Third Level, Phoenix Ballroom
9:00 PM - SM5.7.01
Functionalization of Biomaterials for Enhanced Drug Binding and Controlled Drug Delivery to Control Fungal Biofilms
Jianchuan Wen 1,Ying Deng 2,Yuyu Sun 1
1 Univ of Massachusetts-Lowell Lowell United States,2 University of South Dakota Sioux Falls United StatesShow Abstract
Colonization and biofilm-formation of fungal species on medical device surfaces is a growing clinical concern. We show here that immobilization of conventional biomaterials with functional groups can significantly increase drug binding capacity and control drug release rate to manage fungal biofilms. In our approach, polymeric biomaterials were grafted with poly(1-vinyl-2-pyrrolidinone) (PNVP), poly(methacrylic acid) (PMAA), or poly(2-hydroxyethyl methacrylate) (PHEMA), through plasma-initiated grafting polymerization. With a grafting yield as low as 2 wt%, the three classes of new functionalized biomaterials showed significantly higher drug binding capacities toward miconazole, a widely used antifungal drug, than the original biomaterial control, leading to sustained drug release and potent biofilm-controlling effects against fungal species. Among the three classes of functionalized biomaterials, PNVP-grafted samples provided the highest miconazole binding capability and the most powerful antifungal and biofilm-controlling activities. Increased accessible areas and formation of specific interactions were believed to be the mechanisms for the enhancement in drug binding capability and biofilm-controlling potency, shedding lights on future design of medical devices to fight infections.
9:00 PM - SM5.7.02
Probing Peptide-Graphene Binding Using Single Molecule Force Spectroscopy
Kristi Singh 2,Claretta Sullivan 1,Zhifeng Kuang 2,Steve Kim 2,Patrick Dennis 1,Rajesh Naik 3
1 Materials amp; Manufacturing Directorate Air Force Research Laboratory Wright Patterson AFB United States,2 UES, Inc. Dayton United States,1 Materials amp; Manufacturing Directorate Air Force Research Laboratory Wright Patterson AFB United States3 711th Human Performance Wing Air Force Research Laboratory Wright Patterson AFB United StatesShow Abstract
Functional properties of abiotic materials can be enhanced by peptide binding as demonstrated by peptide influenced anisotropic growth and stabilization of metal nanostructures. Furthermore, adsorbing peptides onto non-biological substrates (graphene, gold, etc.), as biological recognition elements, is an effective strategy for generating selectivity in biosensors. While nature has evolved sequences for biological functions, a priori design of sequence specific interactions in peptide/inorganic material systems requires an understanding of the mechanisms involved in favorable interactions. Peptides identified through phage display to bind inorganic substrates are attractive test cases for understanding the principles of biotic/abiotic interfacial interactions. AFM-based single molecule force spectroscopy (SMFS) provides the sensitivity necessary to measure binding affinities between tethered peptides and inorganic surfaces. AFM studies probing the interactions of the graphene binding P1 peptide (HSSYWYAFNNKT) and graphene, coupled with molecular modeling, will be presented.
9:00 PM - SM5.7.03
Thermal and Mechanical Characterization of Nano-Hydroxyapatite /Poly(Hydroxybutyrate) Composite or Odontological Application
Teresa Castillo 1,Leila Barreto 1,Ruben Rodriguez 1
1 Universidade Estadual do Norte Fluminense Campos Goytacazes Brazil,Show Abstract
The search for an ideal bone substitute has been motivating researches in the last decades. As starting point the metallic, ceramic and polymeric materials were used separately, and today the interest is focused on biocomposites. Nano biocomposite from poly3-hydroxybutyrate (P3HB) and nano hydroxyapatite (HAP) were formulated and dynamical mechanic test and calorimetric characterization were carried out. The homogeneus distribution phases particles and a good adhesion between P3HB matrix and nHA in the nano biocomposites, observed with the help of scanning electron microscopy, justify the highest storage modulus values to P3HB/43%nHAP biocomposite. The results showed that the introduction of nHA increased the stiffness and strength of the polymer matrix led to mechanical properties close to the human bone and it biomaterial not shown any citotoxicity and also had high cellular viability.
9:00 PM - SM5.7.04
Substrate-Independent Robust and Heparin-Mimetic Hydrogel Thin Film Coating via Combined LbL Self-Assembly and Mussel-Inspired Post-Crosslinking
Lang Ma 1,Changsheng Zhao 1
1 Sichuan University Chengdu China,Show Abstract
In this work, we designed a robust and heparin-mimetic hydrogel thin film coating via combined LbL self-assembly and mussel-inspired post-crosslinking. Dopamine grafted heparin-like/-mimetic polymers (DA-g-HepLP) with abundant carboxylic and sulfonic groups were synthesized by the conjugation of adhesive molecule, DA, which exhibited substrate-independent adhesive affinity to various solid surfaces due to the formation of irreversible covalent bonds. The hydrogel thin film coated substrates were prepared by three step reactions: firstly, the substrates were coated with DA-g-HepLP to generate negatively charged surfaces; then, multilayers were obtained via Layer-by-Layer coating of chitosan and the DA-g-HepLP; finally, the noncovalent multilayers were oxidatively cross-linked by NaIO4. Surface ATR-FTIR and XPS spectra confirmed the successful fabrication of the hydrogel thin film coatings onto membrane substrates; SEM images revealed that the substrate-independent coatings owned 3D porous morphology. The soaking tests in highly alkaline, acid, and concentrated salt solutions indicated that the cross-linked hydrogel thin film coatings owned high chemical resistance. Meanwhile, the soaking tests in physiological solution indicated that the cross-linked hydrogel coatings owned excellent long-term stability. The live/dead cell staining and morphology observations of the adhered cells revealed that the heparin-mimetic hydrogel thin film coated substrates had low cell toxicity and high promotion ability to cell proliferation. Furthermore, systematic in vitro investigations of protein adsorption, platelet adhesion, blood clotting, and blood-related complement activation confirmed that the hydrogel film coated substrates showed excellent hemocompatibility. Both the results of inhibition zone and bactericidal activity indicated that the gentamycin sulfate (GS) loaded hydrogel thin films had significant inhibition capability toward both Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacteria. Combined the above advantages, it is believed that the designed heparin-mimetic hydrogel thin films may show high potential for applications in various biological and clinical fields, such as long-term hemocompatible and drug loading materials for implants.
9:00 PM - SM5.7.05
Enhanced Anti-Tumor Efficiency with Phosphorylcholine as Hydrophlic Shell for Delivery Dox: In Vitro and In Vivo Study
Mengtan Cai 1,Xianglin Luo 1
1 Sichuan University Chengdu China,Show Abstract
Bio-inspired phosphorylcholine has shown great promise as a novel material to construct biocompatible nanocarriers. In this study, to make a comparison between the newly emerging nanocarriers containing phosphorylcholine and conventional nanocarriers with poly(ethyl glycol), poly(ε-caprolactone)-b-poly(2-methacryloyloxyethyl phosphorylcholine) (PCL-PMPC) and poly(ε-caprolactone)-b-poly(ethylene glycol) (PCL-PEG) were prepared. The amphiphilic copolymers self-assembled into small and uniform micelles, as nanocarriers for DOX with high drug content. PCL-PMPC micelles exhibited faster drug release at pH 5.5 than that of PCL-PEG micelles. In vitro cell toxicity, confocal laser scanning microscopy and flow cytometry results showed PCL-PMPC micelles presented effective cellular uptake and higher capability to kill tumor cells. In vivo imaging and pharmacokinetics investigation revealed that PCL-PMPC micelles got a better capability to prolong the circulation time of drug and accumulation at the tumor site. In vivo antitumor activity demonstrated that PCL-PMPC micelles had the better therapeutic efficacy to tumors than PCL-PEG micelles, and all the micelles appeared less side effect. Therefore, PCL-PMPC micelles are deemed as promising drug carriers for cancer therapy.
9:00 PM - SM5.7.06
The Hydrophobic to Superhydrophilic Change Induced by PHB in PEG:PHB Electrospun Membranes by Plasma Treatment
Ma Guadalupe Rojano-Molina 1,Maraolina Dominguez-Diaz 2,Horacio Martinez-Valencia 3,Jose Escorcia-Garcia 4,Ruth Fabiola Balderas-Valadez 2
1 Facultad de Ciencias Químicas e Ingeniería Universidad Autónoma del Estado de Morelos Cuernavaca Mexico,2 Centro de Investigación en Ingeniería y Ciencias Aplicadas Universidad Autónoma del Estado de Morelos Cuernavaca Mexico3 Instituto de Ciencias Físicas Universidad Nacional Autónoma de México Cuernavaca Mexico4 CIVESTAV-Unidad Saltillo Ramos Arizpe MexicoShow Abstract
The plasma treatment can be used in polymers to remove contaminants and to functionalize their surface for various applications. In particular, the plasma treatment changes the wettability of surfaces making them hydrophilic, which has been found to be favorable for cell growth on materials. The polyethylene glycol (PEG) and polyhydroxybutyrate (PHB) are polymers that exhibit different wettability properties and degradation rates being the PEG that material with more hydrophilicity and higher degradation rate. In this work was studied the effect of plasma treatment on the wettability of composite materials constituted of PEG and PHB in the form of films and membranes, processed through the spin-coating and electrospinning techniques. In order to do this, different polymeric solutions of PEG:PHB with proportions of 100:0, 80:20, 50:50, 20:80, and 0:100 were prepared. The wettability of the samples was observed by measuring the contact angle by the sessile drop technique. It was found that the hydrophobicity of the composites processed by electrospinning is higher than those processed by spin-coating, using the same proportions of PEG:PHB. Then, the electrospun membrane materials were treated in argon plasma for 1 second. The SEM micrographs showed a significant increase in roughness of the membrane with 100% of PEG content (100:0) as well as better homogeneity in those with proportions of 80:20 and 50:50. The samples with higher content of PHB (20:80 and 0:100) did not show changes in the fiber morphology. Regardless the roughness of the Ar-treated samples, the contact angle of the materials was decreased resulting in values similar to the obtained by spin-coating, or even lower. Particularly, this was observed in the materials constituted with PEG:PHB contents of 20:80 in which the film, the membrane and the plasma-treated membrane showed contact angles of 49, 72, and 0° (superhydrophilic), respectively. The analysis by FTIR spectroscopy indicated the presence of oxygen groups and hydroxides in the samples treated with Ar plasma, which was more significant in those samples containing PHB. These species are formed by the interaction of the free radicals formed during the plasma and the atmospheric oxygen, which helps the hydrophilicity of the samples resulting in a decrease of the contact angle. Thus, the plasma treatment can change the hydrophobicity of the materials to superhydrophilic surfaces. Furthermore, the membranes obtained from polymeric solutions with high PHB content (20:80 and 0:100) kept their shape after their exposure to plasma, which is a characteristic desirable for its use as supports for cell culture.
9:00 PM - SM5.7.07
Antimicrobial Effect of Photo-Functional Polymers Generating Reactive Oxygen Species
Yong-Rok Kim 1
1 Yonsei Univ Seodaemoongu Korea (the Republic of),Show Abstract
Reactive oxygen species (ROS) have been a long time subject in chemical, environmental, and bio-medical science due to its strong reactivity and selectivity, and the involvement with metabolism of cell and organs(1). They have many applications such as photodynamic cancer therapy, decontamination of blood product, water disinfectant, drug delivery system, and stereo-selective synthesis of drug in life science area(2). Therefore, investigation on the photosensitizers with high efficiency of ROS generation is in a great demand(3).
In this study, we report antimicrobial effect of the photofunctional polymer. The photofunctional polymer (PFP) that is the polymer embedded with a photosensitizer is fabricated. ROS generation from PFP is firstly confirmed with photocatalytic method, and then the singlet oxygen generation from PFP is quantitatively measured by the time and wavelength resolved singlet oxygen phosphorescence spectroscopy. For influence study of ROS, photodynamic inactivation (PDI) effect of photofunctional polymer is evaluated for various bacteria including antibiotic resistance bacteria.
1. Ogilby, P. R. Chem. Soc. Rev. 2010, 39, 3181.
2. Choudhary, S.; Nouri, K.; Elsaie, M. L. Lasers Med. Sci. 2009, 24, 971.
3. Wang, K.-K.; Choi, K.-H.; Shin, H.-W.; Kim, B.-J.; Im, J.-E.; Oh, S.-L.; Park, N.-S.; Jung, M.; Oh, J.-B.; Lee, M.-J.; Kim, H.-K.; Kim, Y.-R. Chem. Phys. Lett. 2009, 482, 81.
9:00 PM - SM5.7.08
Progress towards the Evaluation of Nanopatterned Stents In Vivo
Bryan Woo 2,Xiaolong Ma 1,Duncan Ashby 2,Yuntian Zhu 1,Suveen Mathaudhu 3,Masaru Rao 4
2 Mechanical Engineering University of California, Riverside Riverside United States,1 Materials Science and Engineering North Carolina State University Raleigh United States2 Mechanical Engineering University of California, Riverside Riverside United States,3 Materials Science and Engineering University of California, Riverside Riverside United States2 Mechanical Engineering University of California, Riverside Riverside United States,3 Materials Science and Engineering University of California, Riverside Riverside United States,4 Bioengineering University of California, Riverside Riverside United StatesShow Abstract
Although coronary stenting has become the standard of care for the treatment of advanced coronary artery disease, adverse responses such as restenosis and late stent thrombosis (LST) remain challenges to safety and efficacy. Restenosis is often seen in bare metal stents and is characterized by luminal re-narrowing produced by cellular hyperproliferation in response to implantation-induced injury. Drug-eluting stents address this issue via controlled release of antiproliferative or immunosuppressive drugs. However, this comes at the cost of increased potential for LST, due to delayed healing caused by drug elution. This inhibits reestablishment of the endothelium, thus leaving the stent surface exposed as a thrombogenic trigger.
As we have reported earlier, rational design of nanoscale stent surface topography (i.e. nanopatterning) may provide a new means for addressing these issues by facilitating, rather than delaying, healing. Specifically, using our novel titanium deep reactive ion etching (Ti DRIE) technique, we have demonstrated the fabrication of planar Ti substrates patterned with precisely-defined nanoscale surface gratings, and we have shown that these structures can promote significant enhancement of endothelial cell response in vitro, including increased adhesion and proliferation, cellular morphology reminiscent of the native endothelium, and increasingly athero-resistant phenotype. More recently, using Ti DRIE, we have also demonstrated fabrication of the first nanopatterned stents that are compatible with balloon catheter deployment, thus paving the way towards evaluation of nanopatterning in more physiologically relevant settings. However, despite these successes, the limitation of Ti DRIE to commercially-pure Ti (CP Ti) represents a lingering challenge. This is due to the relatively low strength of CP Ti, which may yield devices that are unable to resist vascular recoil and/or maintain sufficient wall apposition.
Herein, we report our recent efforts to address this limitation through exploration of the potential for using an emerging severe plastic deformation technique, high-pressure torsion (HPT), to produce high strength, nanocrystalline CP Ti substrates for use in nanopatterned stents. We demonstrate that HPT can be used to significantly increase yield strength without adversely affecting ductility, which is a key requirement for balloon-deployed stents. We also demonstrate the fabrication of nanocrystalline CP Ti stents using Ti DRIE, and confirm their compatibility with conventional balloon deployment. Finally, we demonstrate that these devices possess significantly increased radial strength relative to our earlier stents. Collectively, these results represent important steps towards our goal of developing a new therapeutic paradigm, where surface nanopatterning facilitates healing, thus reducing the need for drug elution and other adjunctive pharmacological interventions for mitigation of adverse physiological responses.
9:00 PM - SM5.7.09
Preparation and Characterization of Lignin-Based Activated Carbon Recycled from Industrial Waste Black Liquor for Biomaterial Applications
Donghwan Cho 1,Daeyeon Kim 2,Jeonghoon Kim 1,Oh Hyeong Kwon 1,Won ho Park 3
1 Department of Polymer Science and Engineering Kumoh National Institute of Technology Gumi Korea (the Republic of),2 Korea Research Institute of Chemical Technology Ulsan Korea (the Republic of)3 Department of Advanced Organic Materials and Textile System Engineering Chungnam National University Daejeon Korea (the Republic of)Show Abstract
Most recently, biomass-derived by-products as renewable resources are increasingly interested in academia and industries, due to their natural abundance, sustainability, and low cost. Black liquor is one of the typical biomass-based renewable resources. It is industrial waste obtained from a chemical pulping process of wood. Lignin, which is the secondary abundant natural polymer on earth after cellulose, can be easily extracted from black liquor. Lignin exhibits better thermal stability and higher carbon yield than other biomass-based products. Black liquor has potential as a precursor material for preparing activated carbon through carbonization and activation processes. Such the activated carbon may be utilized in various applications such as filters, water purifying material, biomedical wound dressing material, masks, textiles, etc. Therefore, the objective of the present study is to prepare and characterize lignin-based activated carbon recycled from industrial waste black liquor for biomaterial applications such as wound dressing.
In this work, lignin was extracted from industrial waste black liquor by adjusting the pH value with sulfuric acid, and then by neutralizing through filtering and washing it with distilled water. Carbonization and steam activation processes of the extracted lignin were carried out using a tube-type carbonization furnace and a steam activation furnace, respectively. The carbonization temperatures of 600, 850, and 1000°C were used, respectively. The steam activation process was carried out at 850°C with the holing time of 60 min subsequently after the carbonization process at 850°C. The steam injection rate was 3 mL/min. In the both heat-treatment processes, the heating rate was 1°C/min, and a nitrogen gas was purged throughout the processes.
The extracted lignin was characterized through various analytical tools such as ATR-FTIR, TGA, 1H-NMR, and SEM. It has been demonstrated in the present work that lignin was successfully extracted from black liquor and the lignin yield was roughly 11.3% by weight, compared to the initial weight of the ‘as-supplied’ black liquor. The extracted lignin was finely ground. The carbon content and the thermal stability of the carbonized lignin were examined using elemental analysis and thermogravimetric analysis. With increasing the carbonization temperature from 600°C to 1000°C, the carbon yield of lignin was increased and the weight loss was decreased. The SEM images reveal that the carbonized lignin exhibits totally different surfaces from the extracted lignin. The carbonized lignin was activated by a steam activation process and the specific surface area of the activated lignin was approximately 1700 m2/g. The surface topography of the activated carbon was observed using FE-SEM. The result informs that a large number of pores in the activated carbon are well formed by the steam activation.
9:00 PM - SM5.7.10
Continuous Fabrication of Scalable 2D Nanopatterns by Sequential 1D Patterning Strokes for Electronic and Biosensing Applications
Jong G. Ok 1,Ashwin Panday 2,Long Chen 2,Taehwa Lee 4,Moonkyu Kwak 3,Lingjie Guo 4
1 Seoul National University of Science and Technology Seoul Korea (the Republic of),2 Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor United States4 Department of Mechanical Engineering University of Michigan Ann Arbor United States3 School of Mechanical Engineering Kyungpook National University Daegu Korea (the Republic of)2 Department of Electrical Engineering and Computer Science University of Michigan Ann Arbor United States,4 Department of Mechanical Engineering University of Michigan Ann Arbor United StatesShow Abstract
2D planar nanopatterns are of great interest in many fields as they can be utilized to a big array of applications from functional films to thin-film devices. However, typical methods to make 2D patterns based on laser interference and e-beam lithography along with some nonconventional approaches (e.g., self-assembled block copolymer-templated patterning) often suffer from low fabrication throughput, area limitation, and high cost.
To this end, we develop a simple but versatile methodology for scalable and high-throughput fabrication of 2D nanopatterns via sequential continuous 1D nanopatterning strokes enabled by Dynamic Nano-Inscribing (DNI) and Vibrational Indentation-driven Patterning (VIP) . DNI inscribes and VIP indents 1D micro/nano-grating patterns in a continuous manner on flexible substrates with controlled period and depth. By combining these 1D patterning strokes in series, various 2D patterns of desired topology can be continuously ‘direct-written’. Further, by adopting a grating-containing DNI tool in VIP processing, a ‘single-stroke’ 2D patterning can also be realized .
Many applications can benefit from the presented 2D nanopatterning strategy, particularly requiring large area and high throughput. In particular, 2D-DNI realizes a well-defined ‘nanovoid’ pattern which can be capitalized in manifold applications such as electronics and bioengineering templates especially requiring good scalability and reproducibility. As an example, we present one specific use of such a nanovoid pattern: a size-selective docking of nanoparticles (NPs) in solution, demonstrated by a microfluidic cell experiment in conjunction with in-depth simulation analysis. Fluorescently labeled, negatively charged polystyrene NPs of the diameter matching to the void size are effectively confined in the positively charged nanovoids. This demonstration may be just one example among what our 2D patterns can be used for, specifically targeting commercially-feasible scales.
* This work was supported by the National Research Foundation of Korea(NRF) Grant funded by the Korean Government(MSIP) (No. 2015R1A5A1037668).
 J. G. Ok, S. H. Ahn, M. K. Kwak, and L. J. Guo, Continuous and high-throughput nanopatterning methodologies based on mechanical deformation, J. Mater. Chem. C, 1, 7681-7691 (2013).
 J. G. Ok, A. Panday, T. Lee, and L. J. Guo, Continuous fabrication of scalable 2-dimensional (2D) micro- and nanostructures by sequential 1D mechanical patterning processes, Nanoscale, 6, 14636-14642 (2014).
9:00 PM - SM5.7.11
Surface Modification of Titanium Dental Implants for Enhancing Bacteriostatic Properties
Oscar Janson 1,Satwik Gururaj 1,Shiuli Pujari-Palmer 1,Marjam Karlsson Ott 1,Ken Welch 1
1 Uppsala University Uppsala Sweden,Show Abstract
Infections caused by bacterial biofilm on dental implants affect a considerable amount of patients. A number of surface modification techniques exist for titanium implants, including anodic oxidation and physical vapor deposition, which are intended to improve implant properties such as integration with the surrounding tissue and reduction of bacterial adherence. A simpler and economically attractive method is soaking the surface in hydrogen peroxide (H2O2), sodium hydroxide (NaOH) and calcium dihyroxide (Ca(OH)2). This method is hypothesized to not only provide antibacterial activity, but also preserve the bioactive properties and biocompatibility of the surface. The aim of this study was to determine if this surface treatment provides an antibacterial effect, as well as examine if the addition of calcium ions results in enhanced bioactivity.
Discs of grade 2 Ti were punched into circular coins with diameter 9 mm and 1 mm thickness. The coins were cleaned and then immersed in H2O2 for 1 h at 90 °C. Subsequently the coins were soaked in NaOH for 15 min. The coins were divided in six test groups where three groups were further soaked in Ca(OH)2 for 15 min and then either heated at 200 °C for 1 h, autoclaved at 125°C 1 h, or simply kept at room temperature for 1 h. The remaining three groups received the same final heat treatment, but without the soaking in Ca(OH)2. [KW1]
To check for bioactivity, coins from each group were immersed in Dulbecco’s PBS enriched with Ca2+ and Mg2+ ions at 37 °C for 7 days. Coin surfaces were inspected for hydroxyapatite (HA) in a LEO 1550 scanning electron microscope.
In order to determine biocompatibility, two cell lines (MC3T3 murine preosteoblasts and human dermal fibroblasts (hDF)) were seeded onto coins from each group. Cell viability was measured after 3 days using the Alamar Blue assay.
Finally, to determine antibacterial activity, coins from each group were checked for H2O2 release by studying the degradation of the organic dye rhodamine B.
Test groups soaked in Ca(OH)2 showed a higher degree of HA formation compared to test groups not soaked in Ca(OH)2, which is an indication of enhanced bioactivity. Coins without heat temperature showed better HA formation than 200 °C and autoclaving. The hDF cells exhibited no changes in cell viability as compared to the control after 3 days. The MC3T3s, however, had greater proliferation on the modified coins compared to the unmodified Ti. The rhodamine B tests showed that four of the six modified surfaces showed approximately 30 % dye degradation after 7 days.
Discussion and conclusions
Calcium ion addition increased the bioactivity, providing more sites for phosphate to bind to calcium. Preliminary tests with rhodamine B suggest an antibacterial activity of the modified surfaces. Future studies will be conducted to further investigate the potential effect with bacteria.
9:00 PM - SM5.7.12
A Study for Detecting Sodium in Silicon-Based Continuous Glucose Sensors after Fluid Percolation via a MeV 23Na (α, α) 23Na Nuclear Resonance and Ion Beam Analysis
Yash Pershad 2,Abijith Krishnan 2,Nithin Kannan 2,Tiffanie Lee 4,Rachel Neglia 4,Mark Mangus 1,Robert Culbertson 1,Nicole Herbots 3,Barry Wilkens 5,C Watson 3
1 Department of Physics Arizona State University Tempe United States,2 BASIS Scottsdale High School Scottsdale United States,1 Department of Physics Arizona State University Tempe United States,4 Tempe Preparatory Academy Tempe United States1 Department of Physics Arizona State University Tempe United States1 Department of Physics Arizona State University Tempe United States,3 SiO2 Nanotech LLC Phoenix United States1 Department of Physics Arizona State University Tempe United States,5 LeRoy Eyring Center for Solid State Sciences Arizona State University Tempe United States3 SiO2 Nanotech LLC Phoenix United StatesShow Abstract
Percolation of blood and of interstitial fluids into implantable continuous glucose sensors (CGS) used by diabetics contributes to the present 3-7 day limit on sensor lifetime. Na+ mobile ions from interstitial fluids and from blood permanently damage Si-based CGS sensors. This work first investigates the direct detection of Na percolation via Ion Beam Analysis (IBA) in sensors that have been exposed to bodily fluids. Detecting an element in IBA depends on the ratio of its atomic number to that of the substrate. Because of Na’s low atomic number (Z=11) and low mass ratio of Na to Si (23:28), the Si substrate signal from the sensor can obscure the Na signal and prevent Na detection on Si via traditional Rutherford backscattering.
The increase in scattering cross section, and thus detectability of Na, is characterized for a little-known nuclear resonance, 23Na (α, α) 23Na, observed around 4.7 MeV. To measure more precisely this resonance’s energy, width, and resonance factor, the ion beam energy was calibrated via three well-known signals: emission of 5.486 ± 0.007 MeV α particles by a 241Am source, the 12C (α, α) 12C nuclear resonance with 4.265 ± 0.055 MeV α particles, and the 16O (α, α) 16O nuclear resonance with 3.038 ± 0.003 MeV α particles. Next, the increase in cross section due to the resonance is measured via the known composition of NaF thin films on Si(100) samples by scanning α-particle energies around 4.7 MeV. The calibration of this 23Na (α, α) 23Na nuclear resonance yields a resonance energy of 4.696 ± 0.180 MeV and an increase in scattering cross section of 41 ± 7 %. The increase of Na detection by IBA via nuclear resonance is thus statistically significant, but still small compared to the C resonance (1700 %) and the O resonance (210 %). Thus, it may not be sufficient for trace amounts of Na in Si.
Therefore, in addition to detecting Na ions by IBA, the relative abundance of other elements in blood is examined along with these elements’ detectability by IBA, as an alternative to track fluid percolation and Na diffusion in damaged sensors. Detecting more abundant, heavier elements in blood and interstitial fluids can indirectly improve detection of fluid percolation and the tracking of Na+ ions in sensors. Sorting elements and their relative abundance in blood shows that total blood Ca typically reaches an average of 9.42 x 103 μg/dL. This is 30 times higher than the average blood Na, which reaches 3.42 x 102 μg/dL. Next, the expected magnitude of the Ca signal is computed via the Rutherford Universal Manipulation Program (RUMP). RUMP models IBA spectra. Two sets of experiments were simulated with RUMP using a layer of dried blood on top of either Si and C substrates. The results indicate that Ca is the dominant species detected, yielding 1000% higher signal than Na, due to its high relative abundance and atomic mass (40 Daltons, twice as much as Na).
9:00 PM - SM5.7.13
Synthesis of Lactosylated Albumin Microparticles as Vehicle for Specific Drug Delivery to Bacterial Pathogens
Jose Andre-i Sarabia-Sainz 1,Gabriela Ramos-Clamont Montfort 2,Ana Guzman-Partida 2,Erika Silva-Campa 1,Martin Pedroza-Montero 1,Luz Vazquez-Moreno 2
1 Universidad de Sonora Hermosillo Mexico,2 Bioquímica de proteínas y glicanos Centro de Investigación en Alientación y Desarrollo Hermosillo MexicoShow Abstract
Host recognition is the first step to infection of many diseases caused by bacterial pathogens. Recognition to specific host molecules is attractive to obtain targets for drug delivery systems. In this study, lactosylated albumin (BSA-glucose-β (4-1) galactose or BSA-Lac) microspheres were formulated as specific delivery vehicle to enterotoxigenic Escherichia coli K88 that presents a galactose specific adhesin. Oxytetracycline was loaded in polymerized microparticles and characterized by several physico-chemical techniques such as scanning electron microscope, fluorescent microscopy and in vitro drug deliver. The biological interactions were evaluated with plant galactose specific lectins and E. coli K88. Yield and encapsulation efficiency were above to 87 and 60 % respectively. The particle size was 7.9 to 11.6 µm. In vitro release of oxytetracycline showed a biphasic first order model. The biological interaction with lectins from Ricinus communis and Sophora japonica indicated that galactose was available, but affected by the amount of crosslinker in the formulation. Also, E. coli K88 recognized all microspheres containing BSA-Lac in the matrix. These results show that lactosylated microspheres could be used as generalized approach for the treatment of adhesin containing bacteria.
9:00 PM - SM5.7.14
Antibody-Antigen Interaction Applicable for Drug-Nanocarriers Targeting to Tumor Cells
Alexandra Karasova 1,Denisa Lizonova 1,Monika Majerska 1,Nina Sarvasova 1,Pavel Ulbrich 1,Vlastimil Kral 2,Frantisek Stepanek 1
1 University of Chemistry and Technology, Prague Prague 6 Czech Republic,1 University of Chemistry and Technology, Prague Prague 6 Czech Republic,2 Institute of Molecular Genetics of the ASCR, v. v. i. Prague Czech RepublicShow Abstract
Currently used treatment of cancer is mostly based on unspecific drugs and leads to severe side effects. On the contrary curative nanocarriers allow delivery of an active substance in higher therapeutic dosage directly to tumors and released it upon an external stimulus and thus increased efficacy and tolerability of the anti-cancer therapy. We developed a targeted drug delivery system which can find the target through antibody-antigen interaction. Silica nanoparticles (SiO2) are synthesized as a model nanoparticle and covered by a monoclonal antibody IgG M75 highly specific to the antigen Proteoglycan Domain of human Carbonic Anhydrase IX (CA IX). The CA IX is transmembrane protein highly expressed, due to hypoxia, on many types of fast growing solid tumors whereas physiological expression is restricted only in stomach and biliary duct. Two types of nanoparticles were prepared - silanized and amine. The specificity of the interaction between IgG M75 and CA IX and strength of coupling antibody to nanoparticles were tested by ELISA-like test. Both nanoparticles showed high binding specificity for the CA IX, however the antibody was not attached sufficiently strong to the silanized nanoparticles while amine-SiO2 nanoparticles showed high stability during the test of the strength of binding. These amine-SiO2 nanoparticles were used in the following experiments which are shortly described. Amine-SiO2 particles were incubated with blood plasma to evaluate an amount and types of adsorbed plasma proteins. The determination of specific binding of nanoparticles with IgG M75 was done on HT-29 cell line (expressing CA-IX). Various amount of antibody was coupled with amine-SiO2 particles to test an optimal coverage of nanoparticles surface. The final tested surface modification was various length of methoxypolyethylene glycol amine (PEG) chains attached to amine-SiO2 nanoparticles to test an optimal length of PEG, which makes these nanoparticles “invisible” for immune system (so-called Stealth particles) but it does not hamper the binding ability of surface bound antibodies to antigen molecules.
9:00 PM - SM5.7.15
Cancer Extravasation Dynamics in an in vitro Blood Vessel Model
Cristina Bertulli 1,Yan Yan Shery Huang 1
1 Univ of Cambridge Cambridge United Kingdom,Show Abstract
Extravasation of cancer cells from the blood vessel, which involves the trans-endothelial migration and tissue invasion, remains a less well understood process in cancer metastasis. Understanding the mechanisms underlying the extravasation process is of fundamental importance in developing therapeutic targets for the prevention of metastasis. The aim of this research is to investigate breast cancer extravasation in vitro, using a microfluidic system with adjustable biophysical and biochemical factors, to mimic the 3D in vivo vascular microenvironment. In particular, the device is fabricated to mimic the interface between the blood vessel wall and the surrounding extracellular matrix. Using this microfluidic system, breast cancer cell extravasation from the blood vessel to the artificially simulated extracellular matrix was observed. Combining this microfluidic platform with an automated image analysis algorithm, cancer cell morphological changes during the migration process were quantified and they were found to be microenvironment-dependent. In particular, cancer cells were observed to exhibit invadopodia-like protrusions during the invasion process and the presence of endothelial cells forming the vessel lumen was found to sustain the cancer cell invasion into the matrix.
9:00 PM - SM5.7.16
Stimuli-Sensitive Hydrogel-Silicone Composites of Co-Continuous Structures
Junseok Kim 1,Suyeong An 1,Jonghwi Lee 1
1 Chemical Engineering and Material Science Chung-Ang University Seoul Korea (the Republic of),Show Abstract
The incorporation of hydrogel into silicone could be a solution of the conventional problems of silicone rubbers in contact with aqueous solutions or hydrophilic materials. Furthermore, since both extremely hydrophilic and hydrophobic materials have antifouling properties, their composite could be an interesting class of antifouling materials. However, due to their completely different surface energies, the fabrication of hydrogel-silicone composites has seldom been reported. In here, novel composites of polydimethylsiloxane (PDMS) and poly(N-isopropylacrylamide) (PNIPAm) hydrogel were developed. PNIPAm hydrogels having 3-D continuous porous structures were first prepared by directional melt crystallization, and PDMS (80 wt%) was infiltrated into the pores of PNIPAM (20 wt%) to obtain hydrogel-silicone composites of 3D co-continuous structures. Cross-section observation could not distinguish PNIPAm phases from PDMS phases, but after swelling in water, the 3D continuous structures of PNIPAm became distinct on SEM, whose width was ca. 50 μm. Temperature-sensitive volume transition behavior was observed in the resulting composite materials in water, whose swelling ratio spanned from 80% to 800%. Upon swelling, water contact angle dramatically decreased from 125° to 0°. When an anisometric structure was introduced into the films by locating more PDMS on one side, swelling induced significant bending moment. Although the swelling of composite at 4 °C took more than 48 hrs, deswelling at 40 °C back to its original size took only 10 min. These unique properties of hydrogel-silicone composites of 3D co-continuous structures could make the novel composites useful for the future applications such as soft robotics, sensors, lap-on-a-chip, etc.
9:00 PM - SM5.7.17
One Step Fabrication of Superporous Inorganic-Organic Hybrid Surfaces
Sangwon Chi 1,Jonghwi Lee 1
1 Chung-Ang University Seoul Korea (the Republic of),Show Abstract
Superhydrophobic surfaces have been intensively investigated as a solution of surface contamination. Regularly patterned or porous surfaces of different pattern (or pore) sizes have been intensively investigated as self-cleaning surfaces. As a separate mechanism for clean surfaces, antifouling have been investigated for the improvement of membrane performance, coating or paint durability, etc. Incorporation of inorganic particles such as TiO2, could dramatically improve the antifouling properties of polymeric surfaces by decreasing protein adsorption tendency. Herein, the combination of these effective mechanisms, superporous surface and inorganic/organic hybrid antifouling surface, into a single surface treatment step was developed, which was simple and fast. Directional melt crystallization (DMC) technique of inorganic dispersion was applied onto the surface of various polymeric surfaces. DMC is a surface treatment technique which can easily manufacture homogeneous porous structures. The fabricated hybrid composite surfaces had patterned superporous structures, and inorganic particles were successfully embedded in the pore walls, whose distribution had a gradient as a function of depth. As temperature before DMC started (precooling temperature) decreased, the pore size of surface decreased from 30 to 5 um. By this DMC treatment, water contact angle increased from 81.5° to 153.7°. While the existence of inorganic nanoparticles changed the water contact angle by fewer than 10°, the sliding angle of surfaces showed remarkable changes. With using 1 wt% silica nanodispersion, the hybrid composite surface had 180° sliding angle while the polymer surface without silica nanoparticle had an angle under 30°. This technique can be conveniently applied to the surfaces of common polymers, which could additionally provide advantages such as improving the mechanical durability of superhydrophobic surfaces.
9:00 PM - SM5.7.18
Synthesis and Characterization Disk-Shaped Microparticles by RAFT Polymerization
Taeyoon Kim 1,Ildoo Chung 1
1 Polymer Science and Engineering Pusan National University Busan Korea (the Republic of),Show Abstract
Polymers based on vinyl ketones can be degraded by UV irradiation, known as Norrish reactions. Its copolymers has been used as packing materials, agricultural film and functional materials such as sensing, imaging, microfabrication. Polycaprolactone(PCL), aliphatic polyester, which is composed of hexanoate repeat unit, can be biodegraded by various microbes with different degradation rate from several months to years depending on their molecular weight, crystallinity and environment of degradation. PCL has also been used biomedical field such as tissue engineering, drug delivery system due to its biodegradability, biocompatibility.
Encapsulation of drug into polymeric carriers can provide several advantages over conventional formulations, such as the prevention of drugs from metabolism or degradation. For this reason, biodegradable polymeric particles synthesized from polycaprolactone, polylactide, polyglycolide and its copolymers, have been used as drug carriers via various routes against different demands. Spherical polymeric particles have been intensively studied and synthesized by a variety of method such as spray drying, emulsification methods and so on. Various parameters for drug carrier such as surface of particles, size and shape should be considered. Recently, the effect of particle shape was focused on drug delivery system and intensively studied for spherical particles as well as non-spherical particles. The non-spherical particles was prepared by various methods such as ab initio synthesis, modifying spherical particles.
Controlled radical polymerization(CRP), such as reversible addition fragmentation chain transfer processes (RAFT), atom transfer radical polymerization (ATRP), stable free radical polymerization (SFRP), have been studied for the past few decades. Conventional free radical polymerization (CFRP) is difficult to control molecular weight, polydispersity, functionality and structure because bimolecular termination and disproportionation are occurred between growing radical chains. RAFT polymerization is more easier method than others because RAFT can be carried out same condition with CFRP.
In this study, PCL based triblock copolymer was synthesized by RAFT polymerization followed by the fabrication of microsphere by emulsion method. Disk-shaped particles were prepared by UV-irradiation with the microsphere. In order to polymerize by RAFT method, PCL based macro-CTA(chain transfer agent) was first synthesized by reacting carboxylic acid-terminated CTA with PCL, and used for the synthesis of block copolymer with methyl vinyl ketone(MVK). The morphology of the particles before and after UV irradiation were confirmed by SEM and TEM images and paclitaxel, anti-cancer agent for female cancers, with the disk shape particles release behavior were evaluated by HPLC. PCL based disk-shaped particles would be anticipated to enhance drug release and could find potential application for biomaterials.
Diego Mantovani, Laval University
Håkan Engqvist, Uppsala University
Geetha Manivasagam, VIT University
Ketul C. Popat, Colorado State University
SM5.8: Surfaces and Cells
Friday AM, April 01, 2016
PCC North, 200 Level, Room 232 B
9:30 AM - *SM5.8.01
Micropatterned Surfaces with Peptides as Extra-Cellular Matrix Mimics
Ibrahim Bilem 1,Pascale Chevallier 1,Laurent Plawinsky 2,Eli Sone 3,Marie-Christine Durrieu 2,Gaetan Laroche 1
1 Materials Engineering Université Laval Quebec Canada,2 Institute of Chemistry and Biology of Membranes and Nanoobjects Bordeaux France3 Department of Materials Science and Engineering University of Toronto Toronto CanadaShow Abstract
Several protocols were proposed to induce osteogenic differentiation of mesenchymal stem cells (MSCs) in vitro. Nevertheless, producing clinically relevant volumes of bone tissue with adequate stiffness remains the major drawback. This is mainly due to the lack of abundant sources of autologous MSCs and efficient in vitro cell culture models to specifically differentiate MSCs into specialized cells. In vivo, MSCs differentiation is regulated by several signaling molecules sequestered within their extracellular matrix (ECM). Therefore, we proposed to create an artificial ECM on model material surfaces by grafting and micropatterning both adhesive RGD peptide and osteo-inductive BMP-2 mimetic peptide. Indeed, RGD and BMP-2 mimetic peptides were shown to act synergistically to enhance the differentiation of pre-osteoblast cells into mature osteoblast. In addition, surface microstructuration, was demonstrated to improve cell adhesion and differentiation. In this context, RGD and BMP-2 mimetic peptides were grafted on aminosilane-modified glass surfaces. Photolithography was used to graft these peptides as triangular, rectangular, or square micropatterns exhibiting a constant surface of 50 square micrometers. hMSCs were cultured on different micropatterned surfaces up to 4 weeks in basal media, then, fixed and fluorescently stained for STRO-1 as stem cells marker and Runx-2 and Osteopontin (OPN) as specific osteogenic markers. The surface characterization results confirmed that both RGD and BMP-2 mimetic peptides were covalently grafted on glass substrates, and that their density was 0.7 and 1 by square millimeter, respectively. The micro-scale distribution of peptides was clearly evidenced and precisely defined. The biological results showed that hMSCs behave differently depending on the micropattern shape. Fluorescent images showed that all micropatterned surfaces induced hMSCs commitment into specialized cells, as revealed by the expression of STRO-1 only on glass substrate. On the other hand, quantitative analyses of fluorescently stained osteogenic markers confirmed that hMSCs were committed towards the osteoblastic lineage. Moreover, results clearly showed that triangular and square peptide micropatterns up-regulated the expression of both osteogenic markers Runx-2 and OPN compared to rectangular micropatterns. In conclusion, we successfully developed different peptide micropatterned surfaces as ECM mimics in order to investigate hMSCs switch into differentiated cells. Biological results clearly demonstrated that triangular and square peptide micropatterns significantly enhanced osteogenic commitment of hMSCs. These biomimetic surfaces may be used as in vitro models to better understand stem cells response to their microenvironment, thus facilitating the production of specifically differentiated cells for bone tissue engineering applications.
10:00 AM - SM5.8.02
Superhydrophobic Laser-Patterned Grids on PDMS for Droplet Array Formation
Bahador Farshchian 1,Javad Gatabi 1,Steven Bernick 1,Sooyeon Park 1,Ravi Droopad 2,Namwon Kim 1
1 Ingram School of Engineering Texas State University San Marcos United States,2 Materials Science, Engineering and Commercialization Texas State University San Marcos United States,1 Ingram School of Engineering Texas State University San Marcos United States1 Ingram School of Engineering Texas State University San Marcos United States,2 Materials Science, Engineering and Commercialization Texas State University San Marcos United StatesShow Abstract
The wettability of a surface is governed by both its surface chemistry and topography. Superhydrophobic surfaces, defined as surfaces with static contact angles larger than 150° and sliding angles less than 10°, have recently gained considerable attention due to their potential applications for self cleaning, anti-icing, anti-fouling and corrosion resistance. Among the materials which have been used for fabricating superhydrophobic surfaces, PDMS has particularly unique properties. Because of its low surface energy, water repellency, and strong electrical resistance, PDMS is a suitable material to replace glass and porcelain in housing and high-voltage outdoor insulators. PDMS has also been extensively used in soft-lithography for fabrication of microfluidic devices, sensors, and valves thanks to its suitable rheological properties and non-toxicity. In this study, a nanosecond pulsed laser system has been used for the surface treatment of the PDMS. The desired superhydrophobic grids can be directly patterned on the surface of the PDMS by programming a motorized x-y stage and synchronizing the laser system with the stage. Scanning electron microscopy of the laser treated PDMS surface revealed that following the laser treatment the surface becomes considerably rough, forming multi-scale micro and nanostructures. The static contact angle of the water droplet on the laser treated surface was measured at different time intervals. After the laser surface treatment, the static contact angle of water droplet decreased drastically compared to the untreated PDMS and then increased gradually with time until it reached 154° after 5 hours. The grids with different pitch sizes of 2 mm, 1 mm, and 0.5 mm were patterned on the surface of the PDMS. The laser treated samples were used 5 hours after fabrication to ensure the treated areas reached the superhydrophobic state. The proximity of superhydrophobic areas, the areas which are exposed to the laser light, and hydrophobic areas, untreated PDMS, on the PDMS surface will allow spontaneous formation of arrays of droplets when the sample is simply immersed in water and then removed. The size of droplets appears to be a function of the grid cell size and the removal speed. A lifter robot, capable of removing the immersed patterned PDMS at a specific speed out of water, was built in order to measure the droplet size versus removal speed. Results show the droplet size initially increases with the removal speed increase up to a certain speed and then does not change significantly. As an example, the average diameter of droplets was 129 µm at the speed of 5.7 cm/s and increased to 204 µm at the speed of 55.7 cm/s for the 0.5 mm pitched grid. The water droplet arrays can be used as a rapid and reliable tool for the patterning of cells, particles or any components in the aqueous solution. Also, cells can be encapsulated in the droplet and hydrogel arrays for cell screening and culturing.
10:15 AM - SM5.8.03
Biomolecular Structure at the Abiotic Interface
Peter Mirau 1
1 Air Force Research Laboratories Wright Patterson AFB United States,Show Abstract
The structure of biomolecules at the nanomaterials interface is critical for the design of the next generation of biosensors and devices. While phage-display and other methods have been used to identify peptide sequences that recognize inorganic surfaces, the structure of biomolecules at the nanomaterials interface is very difficult to determine. We have been using high resolution NMR in combination with molecular dynamics simulations to determine the structure and dynamics of peptides and DNA aptamers at the metal and metal-oxide surfaces in nanoparticles (NPs). While NMR theory predicts broad lines for biomolecule adsorbed to large NPs, high resolution spectra can be observed when there is fast exchange between the biomolecule free in solution and bound to the NP. We have used these methods to determine the structure of peptides at the interface in 15 nm silica and titania NPs, and the structure of DNA aptamers at the surface of citrate-passivated gold (Au) NPs.
The high-resolution spectra observed under fast exchange conditions allow us to use multi-dimensional NMR to determine the structure of biomolecules at the inorganic interface using the structure determination protocols developed for NMR structure determination in proteins. The results for the silica and titania binding peptides identified by phage display show a well-defined structure at the NP interface, with six of the twelve amino acids in the 12mer peptides in close proximity to the surface. Saturation transfer NMR experiments can be used to determine the orientation of the peptide on the NP surface. The peptides show a similar conformation at the silica and titania interfaces.
Using a similar approach, the hydrogen bonding imino protons in DNA aptamers can be used to measure the interactions of DNA with Au NPs. The NMR results show that folded aptamers interact differently with the Au surface in NP than the unfolded aptamers, single-stranded or double-stranded DNA. This allows for the identification of aptamer folds that interact specifically with the Au NP surface, and leads to a mechanistic understanding of the colorimetric assay for the cocaine binding aptamer using 15 nm Au NP.
Taken together these data show the NMR is a powerful tool for understanding the structure of biomolecules at the NP interface. The study of a library of metal and metal-oxide binding peptides and DNA can lead to an understanding of the sequence-structure-property relationships that will guide the design of the next generation devices using peptides and nucleic acids as biological recognition elements.
11:00 AM - *SM5.8.04
Cell-Laden Gels for Human Bone Marrow-Derived Mesenchymal Stem Cell Delivery
Murugan Ramalingam 2,Deepti Rana 1
1 Centre for Stem Cell Research Vellore India,2 WPI Advanced Institute for Materials Research Tohoku University Sendai Japan,1 Centre for Stem Cell Research Vellore IndiaShow Abstract
Cell-laden hydrogels is an intriguing option to site-specific stem cell delivery into human body by exploiting degradation and mass transportation process of its hydrophilic polymer network in response to external stimulus. In this study, we designed and investigated the impact of polyacrylamide/alginate (PAM/Algi) hydrogels for encapsulation and growth of human bone marrow-derived mesenchymal stem cells (hBMSCs) with five different ratios (1:1, 1:2, 1:3, 1:4 and 1:5). The gels were characterized for their physicochemical properties. Swelling behaviour of the gels was also studied as it facilitates mass transfer of nutrients, oxygen and waste removal by diffusion, which in turn regulates the cell fate and function. Based on physicochemical characteristics, PAM/Algi hydrogel of 1:5 ratios has been selected for cell culture in vitro. For comparison of the cell culture systems (2D Vs 3D), hBMSCs were cultured under a defined condition using three different culture systems, such as on the tissue culture plate (TcP 2D system), on the gel (OnG 3D system) and in the gel (InG 3D system). The results of TcP 2D and OnG 3D systems were found to be comparable in terms of cell attachment, viability and proliferation. In contrast, InG 3D system showed slightly less viability than the other systems but supported a significant proliferation in 7 days. The cells cultured in InG 3D system showed morphology and cellular behaviour quite similar to native tissue-like growth. The overall results suggest that cell-laden gels based on PAM/Algi can be custom designed and used as a carrier for stem cell delivery.
Keywords: Human Bone Marrow-derived Mesenchymal Stem Cells, Cell-Laden Hydrogels, Polyacrylamide, Alginate, 3D Cell Culture, Stem Cell Delivery.
11:30 AM - SM5.8.05
Regulation of Differentiation Direction of Stem Cells by Nanostructures and Physical Cues
Hong Liu 1,Linlin Li 2
1 Shandong Univ Jinan Shandong China,2 Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences Beijing ChinaShow Abstract
Besides the biological growth factors, small organic molecules, and chemical ions, physical signals is the other category of very important factors to tune/regulate the fate of stem cells. Recent years, more attention has been paid on the differentiation of stem cells on the physical signal, including, electric or magnetic field, surface topology of biomaterials, photo irradiation, and even pressure and strain from the materials. With progress of research in this field, some cues of connection between physical signal and bio pathway for differentiation have been discovered. However, more phenomena have still not been understood. Because the physical signals possess controllability and can be localized in a specific area, they are benefit to be used in tissue engineering for tissue regeneration. Therefore, finding new physical approaches for regulation fate of stem cells is a great challenge for alive biomaterials design and applications.
Recent year, some novel phenomena about the effect of physical signal on stem cell differential has been noticed. For example, nano-network morphology of HAP film can differentiate bone marrow mesenchymal stem cells (MSCs) to vascular endothelial cells, surface charges on LiNbO3 wafer can regulate MSCs differentiate to osteogenic cells, and a pressure from biomaterials can differentiate MSCs to neural cells.
In this talk, we will report the above works, and try to explain the reasons for physical signal induced differentiation from both physical mechanism and bio pathways. We believe that the regulation effect of physical signal will attract more attention, and will have great impact for design and application of biomaterials, especially for tissue engineering scaffold, and will bring great progress in tissue regeneration medicine.
11:45 AM - SM5.8.06
Electrochemical Responsiveness of Carbon Nano-Onions and Their Performance for Electrochemical Detection of Biological Redox Molecules
Yan Zhang 1,Doo Young Kim 1,Juchan Yang 1,Allen Reed 1
1 Chemistry University of Kentucky Lexington United States,Show Abstract
Carbon nano-onions (CNOs) are a new class of carbon nanomaterials with a hollow core surrounded by concentric graphitic shells. Because of their unique 0-D structure and surface functionalities, CNOs showed several advantages over 1-D carbon nanotubes (CNTs) and 2-D graphenes such as a better dispersion in electrolyte and the relative easiness of surface modification. In recent years, CNOs have gained increasing attentions in energy storage and catalysis applications. In this talk, electrochemical properties of CNOs and their performance for electrochemical detection of biological redox systems will be present. The biosensing performance of CNOs was studied, in comparison with other commonly used carbon nanomaterials such as multiwalled carbon nanotubes (MWCNTs), graphite nanoflakes (GNFs), and glassy carbon (GC). Cyclic voltammetric and differential pulse voltammetric (DPV) measurements were carried out for the detection of redox-active neurotransmitters: epinephrine, norepinephrine and serotonin. CNOs showed faster electron transfer kinetics and remarkable electrochemical responses with 3-100 times larger oxidation current densities than MWCNTs, GNFs, and GC (CNOs: 2-2.5 mA/cm2, MWCNTs: 0.8 mA/cm2, GNFs: 0.4-0.8 mA/cm2, GC: 0.01-0.3 mA/cm2. Moreover, CNOs showed well-separated anodic peaks in the mixed solution of dopamine, ascorbic acid and uric acid. The linear response range of detecting dopamine by an amperomertic measurement was 0.1 mM to 6 mM with the detection limit of 100nM. These results demonstrated remarkable electrochemical activities of CNOs with high sensitivity, high selectivity, and stable electrode responses.
12:00 PM - SM5.8.07
Are Rapidly Deployable Lubricated Omniphobic Protective Suits against Liquid Phase Biohazards Feasible
Viraj Damle 1,Aastha Uppal 1,Xiaoda Sun 1,Konrad Rykaczewski 1
1 Arizona State University Tempe United States,Show Abstract
Use of personal protective gear made from omniphobic materials in healthcare application can provide enhanced protection from hazardous liquids such as miniscule of liquid containing Ebola virus and pathogenic adhesion within a direct exposure zone, as well as facilitate post-exposure decontamination of the gear. In the past, lubricant swollen polymers have been widely used in bio-fouling applications. [1–5] Recently, lubricant swollen fabric supported polymeric films have been shown as a promising material to make omniphobic protective gears. However, as the polymer needs to be soaked in oil bath for couple of hours before it becomes operational, application of such films could be limited by high lead time (soaking time) and the quantity of oil required to soak the specimen (or gear). In this work we have investigated if underlying fabric in lubricant swollen fabric supported polymeric films can be used as a microfluidic network to transport ‘pressurized’ oil. Such utilization can potentially reduce the oil consumption for making protective gear omniphobic and also reduce the lead time from storage to application.
To systematically assess this idea, we mimicked the fluidic network formed by PDMS encapsulated fabric by fabricating cylindrical cavities in PDMS. Cavities were filled with oil and pressurized using a syringe pump to simulate transport of lubricant though the fabric network. This setup also allowed for quantification of the effect of pressure on the rate of oil diffusion through the PDMS matrix. Change in wettability of exterior surface as a function of time was quantified by measuring contact angle hysteresis and observing surface’s response to impinging droplets. We concluded that pressurizing the lubricant within the range that could be exerted by the healthcare personnel wearing the gear does not appreciably accelerate the oil transport and thus will not cut down the lead time for imparting omniphobicity to the protective gear.
 K. Truby et al. Biofouling 2000.
 C. J. Kavanagh et al. Biofouling 2003.
 D. P. Edwards, et al. Int. Biodeterior. Biodegradation 1994.
 T. G. Nevell et al. Biofouling 1996.
 A. Milne, US Patent, 1977.
 V. G. Damle et al. ACS Appl. Mater. Interfaces 2015.
12:15 PM - SM5.8.08
Effect of Applied DC Bias on PC12 Cell Response on Aerogel Scaffolding
Firouzeh Sabri 1,Kyle Lynch 1,Omar Skalli 1
1 University of Memphis Memphis United States,Show Abstract
Recent studies have demonstrated the biostability and biocompatibility of crosslinked silica aerogels both in vitro and in vivo. Aerogels offer a unique 3-D mesoporous surface morphology and topography that provide unique anchoring sites for cellular attachment and adhesion. It has long been known that neurons respond to electrical stimuli and can be programmed to extend neurites along predetermined paths. This work focuses on the response of PC 12 cells, in vitro, to applied DC bias on an aerogel substrate. The affect of incremental applied potential differences on cultured PC 12 cells is investigated and compared to response of cells cultured on aerogel substrates in the absence of applied potential differences. The applied electric field is expected to influence the behavior of growth and alignment and results will be shared.
SM5.9: Surfaces and Polymers
Friday PM, April 01, 2016
PCC North, 200 Level, Room 232 B
2:30 PM - SM5.9.01
Poly(Aspartic Acid) Hydrogel in Nanofibrous Structure for the Design of Biomimetic Scaffolds
Caidan Zhang 2,Xiaohong Qin 1,Frank Ko 2
1 Donghua University Shanghai China,2 University of British Columbia Vancouver Canada,1 Donghua University Shanghai China2 University of British Columbia Vancouver CanadaShow Abstract
Poly(aspartic acid) (PASP) is a kind of synthesized poly (amino acid)s with various biological functions. Because of its biocompatibility, biodegradability, water solubility and its easy synthesis from renewable resources, PASP is a promising material in biomedical fields covering chelating agent, water treatment, tissue engineering and other biomedical applications. PASP can also be utilized as hydrogel materials with crosslinking. Hydrogel composed of Functional biomaterials with a similar structure of macromolecular-based components in the body have gained remarkable attention in numerous fields, especially for tissue engineering. Here, we devote efforts to the development and application of PASP nanofibrous hydrogel in biological field. Firstly, polysuccinimide, as the intermediate of PASP with a linear structure, was synthesized and electrospun into nanofibers. Then PASP nanofibrous hydrogel was prepared by following crosslinking and hydrolysis treatment of polysuccinimide nanofibers mat. The structure, morphology, pore size distribution were investigated by FTIR, SEM and Through-pore Size Analyzer, respectively. And the swelling ratio of PASP hydrogel nanofibers was measured. By taking advantage of the extremely high porosity of nanofibers structure and excellent water absorbing capability of PASP hydrogel, the PASP nanofibrous hydrogel was swollen and transparent simultaneously after immersed in water within seconds. Even though the large dimension extension of PASP nanofibrous hydrogel in swollen condition, the nanofibers structure provides sufficient constraint to maintain the physical integrity of the hydrogel. And the swelling ratio ranging from 10 to 50 times can be adjusted by crosslinking procedure. As a kind of polyelectrolyte (PE), PASP nanofibrous hydrogel with free carboxyl groups exhibited fast volume transitions induced by pH. To access the potential of PASP nanofibrous hydrogel as a scaffold, the biocompatibility in vitro and some preliminary experiment in vivo were investigated. The results showed that the PASP nanofibrous hydrogel is safe for fibroblasts and adipose derived cells. It also didn’t cause any inflammation in vivo. The PASP nanofibrous hydrogel, combining electrospun structure with hydrogel features and PASP unique characters, is a promising tissue engineering scaffold.
2:45 PM - SM5.9.02
Enzymatically Activated Emulsions Stabilized by Interfacial Self-Assembled Structures
Ines Moreira 1,Tell Tuttle 1,Rein Ulijn 3
1 Pure and Applied Chemistry University of Strathclyde Glasgow United Kingdom,2 Advanced Science Research Center (ASRC) City University of New York New York United States,1 Pure and Applied Chemistry University of Strathclyde Glasgow United Kingdom,3 Hunter College New York United StatesShow Abstract
In this work, the biocatalytic self-assembly of short peptide amphiphiles is used in aqueous/organic mixtures to create on-demand emulsifiers. Aromatic peptide amphiphiles have been extensively studied due to their ability to self-assemble into nanostructures through non-covalent interactions, forming self-supporting gels. An alkaline phosphatase is used to transform phosphorylated precursors into self-assembling aromatic peptide amphiphiles, providing a route to trigger self-assembly of nanofibrous networks and hydrogels. The advantages of self-assembled network formation at interfaces are then combined with enzymatic self-assembly to achieve switchable emulsifiers.
An alkaline phosphatase is demonstrated to initiate the self-assembly process in aqueous buffer by converting precursor aggregates in nanofibres. When in biphasic organic/aqueous systems, these networks form preferentially at the interface, which is shown by different microscopy and spectroscopy techniques. In particular, the phosphatase-mediated conversion of a phosphorylated peptide amphiphile with modest oil-in-water emulsion stabilisation capability to the corresponding dephosphorylated gelator, which forms a stable, permanent interfacial network, is described. Alkaline phosphatase is shown to be active in a chloroform/water medium, in the same extent as it is in aqueous buffer, and also when added to the demulsified mixture at different time points. This gives rise to the possibility of on-demand activation of emulsifying ability, producing switchable emulsions that may be activated by enzyme addition, even after storage of the biphasic mixture for several weeks.
Experimental (Fluorescence and FTIR spectroscopy) and computational techniques (Atomistic Molecular Dynamics) are combined to show that the self-assembly process of aromatic peptide amphiphiles occurs through aromatic interactions and hydrogen bonding to generate a nanostructured network at the water/organic solvent interface. The stability of the emulsions and the possibility of “switching-on” the emulsifying ability provide a promising tool for mixing applications in different chemical processes for the pharmaceutical and cosmetics industries.
3:15 PM - SM5.9.04
Surfactant Enhancement of Antenna Effect in DNA FRET Structure
Taeseok Oh 1,Michael Heller 1
1 University of California San Diego La Jolla United States,Show Abstract
Three surfactants (Triton X-100, CTAB and SDS), which induce less emission quenching by reducing dimerization of dyes, was investigated in order to enhance the antenna effect in FRET from three fluorescent donor dyes (TAMRA) to one fluorescent acceptor dye (TexasRed) attached at the middle of 21mer dsDNA. Even though the TexasRed acceptor was absent in the DNA, a strong hydrophobic interaction among the three TAMRAs conjugated on DNA strand caused emission quenching and absorbance shifting, which indicates the dimerization of the TAMRAs. When the inter-TAMRA distance was closer and the TAMRA dyes were on a flexible single strand, the dimerization occurred more seriously. When Triton X-100 was added to the solution, the dimerization did not change due to the neutral charged surfactant, which does not interact with the DNA strand. By increasing the CTAB concentration to 100 uM and above, the neutralized DNA backbone by cationic surfactant induced the aggregation, resulting enhacement of antenna effect due to CTAB molecules covering or sheathing the fluorescent dyes and suppressing the quenching by dimerization. Even though SDS alone did not affect the emission quenching due to repulsive forces between DNA and SDS micelles, with the addition of cations, such as sodium and magnesium, the dimerization and the emission quenching were reduced significantly. It is concluded that SDS micelle, which approached the DNA strand when the repulsive force was screened by the cations, sheathes/shields/insulates three TAMRA dyes conjugated on a DNA strand, reducing the dimerization and thus recovering the fluorescent emission.
When the three TAMRA conjugated DNA strand and the TexasRed conjugated complementary strand were hybridized without surfactants, formation of dimers such as homodimer by donor-donor stacks and heterodimer by donor-acceptor stacks caused the emission quenching and low antenna effect in the DNA FRET structure. Similar results as three TAMRA conjugated DNA strand without acceptor dye, SDS micelles with magnesium reduced dimerization and enhanced the antenna effect between dyes conjugated on DNA. Overall, this study opens the door for using surfactants with cations to reduce the quenching by dimerization and to improve the antenna effect in DNA FRET structures containing multi-donor and acceptor fluorescent dye molecules.
4:00 PM - SM5.9.05
Intercalated Water Layers Promote Thermal Dissipation at Bio-Nano Interface
Zhiping Xu 1
1 Tsinghua University Beijing China,Show Abstract
The bio-nano interfaces conveying energy and information between biological materials and functional nanodevices are of vital importance in developing nanotechnology-enabled biomedical applications. We identify layered water structures in a nanocap between graphene and lipid bilayer, distinctly different from its bulk form with thickness below a critical value of ~1.0 nm. We examine thermal energy transport and dissipation across this interface, and determine the critical value for power generation in graphene, beyond which significant amount of heat will be accumulated in the membrane and the biological tissues will be disturbed. We find that the intercalated water layers under nanoconfinement play an important role in mediating the interfacial thermal coupling, and efficiently enhance the thermal dissipation. An analytical model is then developed to predict thermal perturbation to living systems. These findings provide a basis for rational design of nanostructure-enabled biosensing technology that measures changes in physiological conditions, and have the potential for developing thermotherapic applications through controlling the temperature at the bio-nano interface.
4:15 PM - SM5.9.06
Phosphorycholine Polymer Nanocapsules Prolong the Circulation Time and Reduce the Immunogenicity of Therapeutic Proteins
Yang Liu 1,Jie Li 1,Yunfeng Lu 1
1 Univ of California-Los Angeles Los Angeles United States,Show Abstract
Protein therapy, which delivers therapeutic proteins to correct disorders, has been considered as the safest and most direct approach for treating diseases. However, the application of protein therapies is highly limited by the lack of efficient strategies for protein delivery, resulting the fast clearance of therapeutic proteins after administration in vivo. Here we demonstrated a novel strategy that can significantly prolong the circulation time of therapeutic proteins as well as minimize their immunogenicity. This is achieved by encapsulating individual protein molecule with a thin layer of crosslinked phosphorycholine polymer that resists protein adsorption. Through extensive cell studies, we identified that the crosslinked phosphorycholine polymer shell could effectively prevent the protein from phagocytosis by macrophages, which play an essential role in the clearance of nanoparticles in vivo. Moreover, the polymer shell prevents the encapsulated protein from being identified by immune cells, which suppress the immune responses against the therapeutic proteins effectively. This work provides a feasible method to prolong the circulation time and reduce the immunogenicity of therapeutic proteins, which may promote the development and application of protein-based therapeutics in the treatments for many diseases.
4:30 PM - SM5.9.07
Solution Exchange Lithography
Christian Pester 1,Kaila Mattson 1,David Bothman 1,Kenneth Lee 1,Benjaporn Narupai 1,Emre Discekici 1,Daniel Klinger 1,Craig Hawker 1
1 Univ of California-S Barbara Santa Barbara United States,Show Abstract
We describe the design and use of a novel experimental setup to combine light-mediated and flow chemistry for the fabrication of sophisticated, and advanced surface-grafted polymer brushes. Using light-mediated, surface initiated controlled radical polymerization processes and post-functionalization via well-established, and highly efficient click chemistry we are able to produce thin polymer brush films of previously unimaginable complexity. The flow setup allows us full flexibility to exchange both lithographic photomask patterns and chemical environments within the flow reactor at will, and readily allows fabrication of multidimensional thin film architectures. These have been shown to be increasingly relevant to numerous applications, including but not limited to, biomedical applications, chemical sensing, selective wetting, and microelectronics. Numerous advanced characterization techniques, including X-ray photoelectron spectroscopy, dynamic secondary ion mass spectrometry, X-ray reflectivity, and atomic force microscopy are used to provide unambiguous evidence for the complex patterns and their functionality.
4:45 PM - SM5.9.08
Nanoscale Chemical and Topological Imaging of Collagen with Photo-Induced Force Microscopy
William Morrison 1,Jinhui Tao 2,Katherine Park 1,Derek Nowak 1,Sung Park 1,James De Yoreo 2
1 Molecular Vista Inc San Jose United States,2 Pacific Northwest National Laboratory Richland United StatesShow Abstract
Collagen is the major structural protein of bone, dentine and the extracellular matrix and can template the nucleation and growth of numerous mineral phases. Collagen meso-scale architecture on surfaces, which is critical for its function, is controlled by the relative magnitude of collagen-substrate (C-S) and collagen-collagen (C-C) interactions. Thus, understanding the nature of these interactions and the mechanisms of assembly on surfaces may enable us to manufacture complex 2D protein assemblies for tissue engineering.
Infrared Photo-induced Force Microscopy (IR PiFM) is based on an atomic force microscopy (AFM) platform that is coupled to a widely tunable mid-IR laser. PiFM measures the sample’s polarizability by detecting the dipole-dipole force that exists between the light induced dipole in the sample and the mirror image dipole in the metallic AFM tip. This interaction is strongly affected by the IR absorption of the sample. Due to its AFM heritage, PiFM acquires both the topography and spectral images concurrently and provides information on the relationship between local chemistry and topology with spatial resolution of ~ 10nm.
PiFM studies on various stages of fibril formation of collagen molecules deposited onto muscovite mica will be presented. The results consist of PiFM spectral images associated with Amide I absorption band. Hyperspectral images, where each pixel consists of PiFM spectrum centered about the Amide I band, are used to study C-C and C-S interactions by tracking the peak shape and position. By enabling imaging at the nm-scale with chemical specificity, PiFM provides a powerful new analytical method for deepening our understanding of bio-materials and facilitating technological applications of such materials.