Symposium Organizers
Andreas Lendlein, Helmholtz-Zentrum Geesthacht
Kevin Cavicchi, University of Akron
LaShanda Korley, Case Western Reserve University
Bernd Rehm, Massey University
Symposium Support
MedShape, Inc.
MilliporeSigma
SM8.1: Stimuli-Sensitive Polymers I
Session Chairs
Tuesday AM, April 18, 2017
PCC North, 100 Level, Room 124 A
11:30 AM - SM8.1.01
Rubber-Like Hydrogel Adhesives
Malav Desai 1 3 2 , Eddie Wang 1 , Ju Hun Lee 1 3 , Seung-Wuk Lee 1 2 3
1 Bioengineering, University of California, Berkeley, Berkeley, California, United States, 3 Biological Systems and Engineering, Lawrence Berkeley National Laboratory, Berkeley, California, United States, 2 Bioengineering, University of California, San Francisco, San Francisco, California, United States
Show AbstractCommonly used tissue adhesives are in the form of polymerizing glues or hydrogels. However, cyanoacrylate-based materials from stiff adhesions and polyethylene glycol or protein based hydrogel adhesives have poor extensibility, both of which can potentially cause damage to the treatment site. In this work, we create a robust, highly deformable hydrogel that can be used as a soft tissue adhesive that employs mussel-inspired chemistry. Instead of focusing on developing complex strategies that involve composites and double networks, we use elastin-like polypeptides (ELPs) to create highly flexible and resilient single-network hydrogels. ELPs are recombinantly expressed proteins composed of a tandemly repeated pentapeptide, ‘Val-Pro-Gly-Xaa-Gly’, derived from mammalian elastin. The guest residue ‘Xaa’ can be anything other than a proline. ELP is ideal for developing a highly extensible hydrogel due to its characteristic behavior like an entropic spring that recoils to lower its entropy when stretched. We designed our ELPs to contain reactive amine containing ‘Lys or thiol containing ‘Cys’ residues only at the ends of the polymer chain. This allows us to crosslink the ELP chains into a near-ideal network and utilize the entire length of the polymer during hydrogel extension. We further designed the ELP chains to contain ‘Glu’ guest residues, adding carboxylic acid functional groups. The carboxylic acids are modified with dopamine to enable the hydrogels to undergo mussel-like adhesion on wet surfaces. In this manner, we create protein-based rubber-like resilient hydrogels and characterize their mechanical properties and adhesiveness to wet surfaces such as tissues.
11:45 AM - *SM8.1.02
Evolution of Self-Oscillating Polymer Gels as Advanced Materials
Ryo Yoshida 1
1 , University of Tokyo, Tokyo Japan
Show AbstractIn living systems, there are many autonomous and oscillatory phenomena to sustain life such as heart palpitations and breathing. We developed “self-oscillating” polymer gels that undergo spontaneous cyclic swelling–deswelling changes without any on–off switching of external stimuli, as with heart muscle. The self-oscillating gels were designed by utilizing the Belousov-Zhabotinsky (BZ) reaction, an oscillating reaction, as a chemical model of the TCA cycle. We have systematically studied these self-oscillating polymer gels since they were first reported in 1996 (JACS). Potential applications of the self-oscillating polymers and gels include several kinds of functional material systems, such as biomimetic actuators, mass transport systems and functional fluids. For example, it was demonstrated that an object was autonomously transported in the tubular self-oscillating gel by the peristaltic pumping motion similar to an intestine. Further, self-oscillating polymer brush surface was prepared by SI-ATRP and the dynamic behavior was evaluated. Besides, autonomous viscosity oscillation was realized utilizing microgels, metallo-supramolecular complex, block copolymer solution, etc. Self-oscillation between unimer/micelle or unimer/vesicle (polymersome) structures was also realized for a synthetic block copolymer. At the microscopic level, oscillatory shape deformations of cells are often observed in dynamic behaviors during cell migration, morphogenesis, etc. In many cases, oscillatory behaviors of cells are not simplistic but complex with diverse deformations. We report a more cell-like hollow sphere composed of self-oscillating microgels, that is, a colloidosome that exhibits drastic shape oscillation in addition to swelling/deswelling oscillations driven by an oscillatory reaction. The resulting oscillatory profile waveform becomes markedly more complex than a conventional one. Especially for larger colloidosomes, multiple buckling and moving buckling points are observed to be analogous to cells. In this presentation, our recent progress on the self-oscillating polymer gels is summarized.
12:15 PM - SM8.1.03
Ultra-Stable and Refrigeration-Free Antibody Ionic Liquids
Joseph Slocik 1 , Patrick Dennis 1 , Rajesh Naik 1
1 , Air Force Research Laboratory, Dayton, Ohio, United States
Show AbstractAntibodies represent the gold standard for diagnostic assays (Enzyme linked immunosorbent assay - ELISA), therapeutics (anti-venoms), and the development of antibody based biosensors; however, they require stringent storage and handling conditions in order to retain function. Conversely, the presence of water is very detrimental to antibodies by increasing the rate of hydrolysis and oxidation, destabilizing protein structure, and increasing the susceptibility/sensitivity to elevated temperatures. To counteract the effects of water and limit decomposition; antibodies require constant refrigeration during storage/handling/transport in order to preserve structure, specificity, functionality, and biological activity. As a result, the need for cold chain logistics is a major barrier in resource limited settings; as well as for military medvac operations where equipment weight and accessibility are major tactical concerns. The exclusion of water from antibody preparations is highly appealing and potentially offers a means towards enabling refrigeration-free storage and handling. Antibody nanoscale ionic liquids represent new multifunctional systems that are well suited towards addressing these challenges. Here, we describe the creation of an ultra-stable antibody ionic liquid that is water-free, resistant to extreme temperatures (200°C), biologically active, exhibits a long shelf-life, and does not require “cold chain” logistics. We have produced antibody ionic liquids against apoferritin, a histidine-rich protein from the malaria parasite Plasmodium falciparum, and hemoglobin. Given the diversity of antibodies, this represents a generalizable approach to creating antibody ionic liquids for virtually any antibody.
12:30 PM - SM8.1.04
Functional Hydrogels and Particles from Crosslinked Polymeric Telechelics
Christian Wischke 1 , Miroslava Racheva 1 2 , Florian Stormann 1 3 , Elen Baehr 1 , Andreas Lendlein 1 2 3
1 Institute of Biomaterial Science and Berlin-Brandenburg Center for Regenerative Therapies, Helmholtz-Zentrum Geesthacht, Teltow Germany, 2 Department of Biology, Chemistry and Pharmacy, Freie Universität Berlin, Berlin Germany, 3 Institute of Chemistry, University of Potsdam, Potsdam Germany
Show AbstractTelechelic polymers can be the basis to construct a large variety of functional materials if combined with both suitable crosslinking techniques and shaping into the desired 3D structures. In this contribution, two examples illustrating the variety of advanced polymeric systems realized from telechelics with distinct endgroups will be given.
Hydrophilic 4-arm star shaped telechelics from poly(ethylene glycol) bearing end groups derived from aromatic amino acids can be substrates of enzymes, thereby allowing an enzymatic catalysis of hydrogel synthesis. Due to the efficiency of the enzymatic reaction, it was envisioned that immobilized enzymes could likewise catalyze such reactions. Here, the surface immobilization of mushroom tyrosinase is reported, which theoretically could allow producing hydrogel coatings at devices of any given shape.
Using polyester telechels with photocrosslinkable end groups, hydrophobic materials can be obtained, which also can be structured in the shape of polymer micronetwork particles. Those particles exhibit elasticity allowing deformation and, furthermore, the capacity to actively switch shape [1]. Beyond this, polymer particles with anisotropic shapes as well as particles with expandable volumes will be presented.
[1] Friess F. et al. (2014) Adv Healthcare Mat 3: 1986-1990.
12:45 PM - SM8.1.05
Enzymatic Polymerization of High Molecular Weight ssDNA
Lei Tang 3 , Yaroslava Yingling 2 , Ashutosh Chilkoti 1 , Stefan Zauscher 3
3 Mechanical Engineering and Materials Science, Duke University, Durham, North Carolina, United States, 2 Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina, United States, 1 Biomedical Engineering, Duke University, Durham, North Carolina, United States
Show AbstractThe use of DNA as a polymeric building material transcends its function in biology and is exciting in bionanotechnology for applications ranging from biosensing, to diagnostics, and to targeted drug delivery. Hence, the effectient and precise synthesis of high molecular weight DNA materials has become key to advance DNA bionanotechnology. Current synthesis methods largely rely on either solid phase chemical synthesis or template-dependent polymerase amplification. In contrast, we here exploit the ability of a template-independent DNA polymerase-terminal deoxynucleotidyl transferase (TdT) to catalyze the polymerization of 2’-deoxyribonucleoside 5’-triphosphates (dNTP, monomer) from the 3’-hydroxyl group of an oligodeoxyribonucleotide (initiator). We term this enzymatic synthesis method: TdT catalyzed enzymatic polymerization, or TCEP.
Using in situ 1H NMR and fluorescent gel electrophoresis we found that TCEP kinetics follows a “living” chain-growth polycondensation mechanism, and that like in “living” polymerizations, the molecular weight of the final product is determined by the starting molar ratio of monomer to initiator. We developed a reaction kinetics model that allows us to quantitatively describe the extent of reaction and to predict the molecular weight of the reaction product. We also demonstrate TCEP’s capacity to incorporate a wide range of unnatural dNTPs into the growing chain, such as, hydrophobic fluorescent dNTP and fluoro modified dNTP. Building on TCEP’s synthesis capacities, we invented a two-step strategy to synthesize diblock amphiphilic polynucleotides, in which the first, hydrophilic block serves as a macro-initiator for the growth of the second block, comprised of natural and/or unnatural nucleotides. By tuning the hydrophilic length, we synthesized amphiphilic diblock polynucleotides that can self-assemble into micellar structures ranging from star-like to crew-cut morphologies. The observed self-assembly behaviors agree with predictions from dissipative particle dynamics (DPD) simulations as well as scaling law theory for polyelectrolyte block copolymers. We believe that TCEP advances the synthesis of multifunctional DNA materials, and enables novel applications for this new class of polynucleotide polymers.
SM8.2: Advanced Structured Materials
Session Chairs
Tuesday PM, April 18, 2017
PCC North, 100 Level, Room 124 A
2:30 PM - SM8.2.01
Self-Assembling Nanocomposite Tectons
Robert Macfarlane 1
1 , Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractNanocomposites consisting of inorganic nanoparticles embedded within a polymer matrix are an important class of materials based on integrating two or more disparate phases to achieve physical characteristics that cannot be realized with a single-phase material. Current syntheses typically focus on chemical composition as the primary factor that determines these properties, but nanocomposite characteristics are also dependent on the geometric arrangement of the phases and the chemical interface between them. While structure control in macroscopic composites can be easily achieved via top-down mechanical processing, similar approaches with nanocomposites either provide limited spatial resolution at the nanometer length scale or are undesirably inefficient. Alternatively, self-assembly could in principle produce polymer-nanoparticle composites with well-defined geometries in a parallelizable manner that is amenable to scale-up. However, the major limitations of current techniques are that they either focus solely on ensuring compatibility of the organic polymer and inorganic nanoparticle phases and lack hierarchical structural organization of all constituent components, or utilize structure-directing agents or processing conditions that are not amenable to functional composite architectures. Here, we circumvent these challenges by developing a new class self-assembling building blocks we term nanocomposite “tectons” (NCTs) – irreducible nanocomposite building blocks that are themselves nanocomposite architectures. An NCT consists of a nanoparticle grafted with polymer chains that terminate in functional groups capable of supramolecular binding, where supramolecular interactions between polymers grafted to different particles enable programmable bonding to drive particle assembly. Importantly, these interactions can be manipulated separately from the identity of the organic or inorganic components of the NCT, allowing for independent control of the chemical composition and spatial organization of all phases in the nanocomposite via a single design concept. The development of NCTs therefore enables the next generation of nanocomposites with simultaneous multi-level structure control to precisely dictate material physical properties.
2:45 PM - *SM8.2.02
Advanced Materials from Polymer Hybrids Self-Assembly
Ulrich Wiesner 1
1 , Cornell University, Ithaca, New York, United States
Show AbstractGlobal problems including energy conversion and storage, clean water and human health require increasingly complex, multi-component hybrid materials with unprecedented control over composition, structure, and order down to the nanoscale. This talk will give examples for the rational design of novel functional polymer hybrid materials inspired by biological examples. These materials are often based on the self-assembly of block copolymers as structure directing molecules for polymer-inorganic hybrid materials. Discussion will include formation of synthetic porous materials with amorphous, polycrystalline, and epitaxially grown single-crystal structures. Experiments will be compared to theoretical predictions to provide physical insights into formation principles. The aim of the described work is to understand the underlying fundamental chemical, thermodynamic and kinetic formation principles enabling generalization of results over a wide class of materials systems. Examples will cover the formation of hierarchical structures at equilibrium as well as via processes far away from equilibrium. Targeted applications of the prepared systems will include the development of fluorescent hybrid probes for nanomedicine, nanostructured hybrids for energy conversion and storage devices, as well as the formation of first self-assembled superconductors.
References
1.) S. W. Robbins, P. A. Beaucage, H. Sai, K. W. Tan, J. P. Sethna, F. J. DiSalvo, S. M. Gruner, R. B. van Dover, U. Wiesner, Block copolymer self-assembly directed synthesis of mesoporous gyroidal superconductors, Sci. Adv. 2 (2016), e1501119.
2.) K. W. Tan, B. Jung, J. G. Werner, E. R. Rhoades, M. O. Thompson, U. Wiesner, Transient Laser Heating Induced Hierarchical Porous Structures from Block Copolymer Directed Self-Assembly, Science 349 (2015), 54-58.
3.) E. Phillips, O. Penate-Medina, P. B. Zanzonico, R. D. Carvajal, P. Mohan, Y. Ye, J. Humm, M. Gönen, H. Kaliagian, H. Schöder, H. W. Strauss, S. M. Larson, U. Wiesner, M. S. Bradbury, Clinical translation of an ultrasmall inorganic optical-PET imaging nanoparticle probe, Sci. Transl. Med. 6 (2014), 260ra149.
4.) H. Sai, K. W. Tan, K. Hur, E. Asenath-Smith, R. Hovden, Y. Jiang, M. Riccio, D. A. Muller, V. Elser, L. A. Estroff, S. M. Gruner, U. Wiesner, Hierarchical porous polymer scaffolds from block copolymers, Science 341 (2013), 530-534.
3:15 PM - SM8.2.03
DNA-Inspired Self-Assembly of Nanoscale Electronic Devices
Kuo Yao Lin 1 , Jason Slinker 1 , Alon Gorodetsky 2 , Andrew Bartlett 2
1 Department of Physics, University of Texas at Dallas, Dallas, Texas, United States, 2 Department of Chemical Engineering and Materials Science, The University of California, Irvine, Irvine, California, United States
Show AbstractDespite remarkable examples of difficult-to-produce isolated molecular devices, the scalable nanomanufacturing of such electronics remains at a standstill due to fundamental roadblocks associated with the synthesis of large quantities of modular nanoscale circuit elements. We have introduced a methodology for mass production of nanoscale electronic elements. We have synthesized organic semiconductor moieties within DNA-like scaffolds, leveraging the rapid, efficient, and precise coupling afforded by traditional DNA bioconjugate chemistry. These DNA-inspired nanowires enable the self-assembly of active, nanoscale circuit elements at patterned electrodes. The assembly and electrical performance of these arrayed devices have been characterized through scanning microscopy techniques and custom, automated electrical probe measurements. Our unique and economically viable approach offers a new paradigm for the fabrication of nanoscale electronic circuits.
3:30 PM - SM8.2.04
Designing Nanostructured Functional Gels for Smart Electronics and Electrochemical Energy Devices
Ye Shi 1 , Guihua Yu 1
1 , University of Texas at Austin, Austin, Texas, United States
Show AbstractMultifunctional gel materials with responsive properties are becoming critically important for wide ranging technological applications, from electronics, biomedical devices, to electrochemical energy devices. To enable significantly improved or even unprecedented properties and designed new functionalities, the chemical composition, micro/nano-structures and physical interactions of gel materials need to be delicately controlled. Here we will present our representative works on rational design and chemical modification of gels with function-enriched properties and their applications in smart responsive electronics and electrochemical energy devices. We designed hybrid gels with an interpenetrating binary network structure by using conductive gels with hierarchically porous structure as a “host” matrix and introducing second polymers such as PNIPAM and supramolecular gel with distinct functionalities as “guest”. By tuning the interactions between two polymeric networks and chemically modifying the interface, the hybrid gels exhibited tunable chemical/physical properties and attractive synergistic characteristics: high electrical conductivity, enhanced mechanical properties and unique functionalities such as thermo-responsive sensitivity, room temperature self-healing behavior, which were used for building up smart electronics. I will discuss another recent work on developing the smart electrolyte that can respond to temperature change and regulate the motion of ions owing to its reversible sol-gel transition, thus realizing self-regulated electrochemical devices with thermal safety. Our works revealed the fundamental structure-property-function relationship of these multifunctional gel systems, and provided a unique material platform to enable their promising applications in self-healing, adaptive electronics, and thermoresponsive electrochemical devices.
3:45 PM - SM8.2.05
Assembly of Ligand Stripped Nanocrystals of Arbitrary Composition with Block Copolymers in Thin Film at Both Low and High Inorganic Loading Fractions
Gary Ong 2 1 , Brett Helms 3 , Delia Milliron 1
2 Materials Science and Engineering, University of California, Berkeley, Berkeley, California, United States, 1 Chemical Engineering, University of Texas at Austin, Austin, Texas, United States, 3 , Lawrence Berkeley National Laboratory, Berkeley, California, United States
Show AbstractBlock copolymer directed assembly of nanocrystals present an exciting avenue for enabling bottom up processing of inorganic materials and organic-inorganic composites that harness the merits of both classes of materials along with precise control of structure. One limit in the approach include chemical specificity necessitating nanocrystal surface ligand functionalization prior to assembly to prevent macrophase separation of nanocrystals out of the block copolymer domain. A second limit is the ability to achieve a high loading of nanocrystals in the structure without macrophase separation or kinetic arrest due to effects such as particle jamming. By studying a specific polymer polystyrene-polydimethylacrylamide where the acrylamide block preferentially adsorbs to bare nanocrystal surfaces, we demonstrate that we can achieve assembly of nanocrystals of arbitrary composition as long as the nanocrystals are ligand stripped of their native organic ligands. This system enables assemblies with up to 40 volume percent inorganic loading yielding mesoporous structures via micelle templating. Selection of nanocrystal size determines the placement of nanocrystals within the polymer domain, be it close or farther from the diblock interface, as well as the density of particle placement within the block. Furthermore, solvent annealing is used to relax structures into their thermodynamic microphase separated configuration enabling morphological control.
SM8.3: Stimuli-Sensitive Polymers II
Session Chairs
Tuesday PM, April 18, 2017
PCC North, 100 Level, Room 124 A
4:30 PM - SM8.3.01
Onion-Like Multilayered Capsules Based on Stimuli-Responsive Polymers—Synthesis by a Bioinspired “Inside-Out” Technique
Brady Zarket 1 , Srinivasa Raghavan 1
1 Chemical & Biomolecular Engineering, University of Maryland, College Park, College Park, Maryland, United States
Show AbstractDiverse structures in nature such as eggs, embryos, body parts like the spinal disc, plant seeds, and the onion all have a common structural motif, which is the presence of multiple concentric layers. Individual layers are often composed of distinct materials because the layers serve different purposes. The creation of these structures in nature (morphogenesis) typically proceeds by the initial formation of an inner layer or core, followed by a first shell, and a further progression outwards to add more shells. Here, we draw inspiration from natural morphogenesis to create multilayered polymer capsules by an “inside-out” technique. First, an aqueous gel core is loaded with an initiator. This core is placed in a solution of monomer 1, whereupon a shell of polymer 1 grows around the core. Thereafter, this core-shell structure is loaded with fresh initiator and placed in a solution of monomer 2, which causes a concentric shell of polymer 2 to form around the first shell. This process can be repeated further to obtain multiple layers of distinct polymers. Each polymeric shell grows outward from the surface of the previous shell; thus, the thickness of a given shell steadily increases with time and can be controlled. A highlight of this technique is the ability to juxtapose different polymers next to each other among the concentric layers in an onion-like capsule. For example, layers of a non-responsive polymer can be placed next to either a temperature-responsive or a pH-responsive polymer. By varying the location of the stimuli-responsive layer(s), we demonstrate that the release of solutes (e.g., drugs) from the capsule can be made to follow unique multi-step release profiles as the stimulus is varied.
4:45 PM - SM8.3.02
Stimuli-Responsive Coaxial Electrospun Membranes Using Self-Immolative Polymers
Daewoo Han 1 , Xinjun Yu 2 , Qinyuan Chai 2 , Neil Ayres 2 , Andrew Steckl 1
1 Department of Electrical Engineering and Computing Systems, University of Cincinnati, Cincinnati, Ohio, United States, 2 Department of Chemistry, University of Cincinnati, Cincinnati, Ohio, United States
Show AbstractThe first self-immolative polymer (SIP) nanofiber membrane has been demonstrated in this report. SIPs are polymeric linear molecules that respond to external stimuli by undergoing head-to-end depolymerization.1 The triggered unzipping of the polymer backbone allows the release of the small molecules components contained within the initial polymer. Recently, micro-capsules with an SIP shell have demonstrated the triggered release of embedded materials.
Electrospinning is a highly versatile method for creating continuous fibers ranging from tens of nanometers to microns in diameter and many meters in length. This is accomplished by applying a voltage between a droplet at a nozzle tip and a collecting substrate. Under the proper conditions (solution conductivity, viscosity, etc.), the applied electric field causes a liquid jet to eject from the droplet. During this process the jet elongates, ultimately resulting in a non-woven mesh of fibers with very high surface-to-volume ratio. Furthermore, using coaxial electrospinning2, 3, different characteristics from each polymer in different layer can be combined in a single fiber, providing multi-functionality to the resulting membrane. Materials that can combine normally contradictory properties or components can open the door to many exciting new applications.
In this paper, we report on the successful demonstration of coaxial fibers with SIP/PAN sheath and PVP/dye core. Upon the addition of trifluoroacetic acid (TFA) into solutions, SIP is depolymerized and the inner core is exposed to the solution. SEM observation reveals different fiber morphologies before and after triggering reaction in solution. Coaxial fibers show minimal release of the encapsulated core material in non-triggering condition, while instant release of the encapsulated material is observed when the triggering condition is met. The depolymerization time of SIP/PAN blended fiber membranes is ~ 25X quicker than that of cast SIP+PAN films. The surface property of SIP/PAN fiber membranes is switched from hydrophobic (WCA ~ 110°) to hygroscopic (WCA ~ 0°) upon triggered depolymerization, indicating that the sheath layer becomes hygroscopic PAN-rich material by releasing the hydrophobic SIP molecules.
Combining coaxial fibers with stimulus responsive SIPs can provide on-demand (“triggered”) release of, or exposure to, components embedded within the fibers. Also, due to the nature of electrospinning, electrospun SIP membranes have an extremely high surface area, leading to a much faster and more sensitive response to the stimuli involved in polymer self-immolation process. These unique properties will be extremely beneficial for many important applications, such as bio/chemical sensors, drug delivery, catalyst, self-healing, etc.
1. Sagi, A.; Weinstain, R.; Karton, N.; Shabat, D., J. Amer. Chem. Soc. 2008, 130 (16), 5434
2. Han, D.; Steckl, A. J., ACS Appl. Mater. Interfaces 2013, 5 (16), 8241.
3. Han, D.; Steckl, A. J., Langmuir 2009, 25, 9454
5:00 PM -
DISCUSSION TIME
5:15 PM - *SM8.3.04
Relations between Response Kinetics and Macromolecular Architecture in Oxidation-Sensitive Materials
Richard d'Arcy 1 , Nicola Tirelli 1
1 NorthWest Centre of Advanced Drug Delivery (NoWCADD), School of Health Sciences, University of Manchester, Manchester United Kingdom
Show AbstractThis paper is about about sulphur(II)-containing polymers, aka polysulfides.
Organic polysulfides have a rich history. Their earliest examples date back to the pioneering age of polymer science: Thiokol A was the first synthetic rubber to be commercialized, well before World War II. More recently (‘60s), the anionic polymerization of episulfides has been a favourite model system during the conceptual development of stereoselective and stereoelective polymerizations. Oblivion then fell on polysulfides until the early 2000s, when the REDOX behaviour of sulphur(II), and specifically its easy oxidizability under mild (and also biologically relevant) conditions paved the way for a renewed interest in these structures. These polymers have then been extensively investigated as materials that exhibit a number of response to biological oxidants (Reactive Oxygen Species, ROS), in particular when the oxidation is linked to significant changes both in the hydrophilicity of the materials and in the morphology of the self-assembled structures they form in water.
In this paper we focus on the relations between macromolecular architecture and oxidative responsiveness. Specifically, we discuss the influence of the polymer primary structure (gradient vs. random structures) and of branching (linear vs. star and comb structures) on the kinetics of the response.
In the first case (primary structure), we have focused on the control of the structure of gradients made of two differently polymerizable monomers, i.e. ethylene sulfide and propylene sulfide; the first one is capable of strong inter- and intramolecular association, in a fashion proportional to the length of its homosequences 1. In the second case (branching), we have compared star and comb polymers (figure on the right) to highlight effects of macromolecular crowding 2.
1. R. d’Arcy, A. Siani, E. Lallana, N. Tirelli “The influence of primary structure on responsiveness. Oxidative, thermal and thermo-oxidative responses in polysulfides”, Macromolecules, 48 (2015) 8108-8120.
2. R. d’Arcy, A. Gennari, R. Donno, N. Tirelli “Linear, star and comb oxidation-responsive polymers: effect of branching degree and topology on aggregation and responsiveness” Macromolecular Rapid Communications, 37 (2016) in press
5:45 PM - SM8.3.05
Photoresponsive Multicompartment Capsules for Controlled Release
Kerry DeMella 1 , Srinivasa Raghavan 1
1 , University of Maryland, College Park, Maryland, United States
Show AbstractPolymer capsules are extensively used in modern times for a variety of applications from cosmetics to biotechnology. The characteristic ability of these structures to encapsulate material and to selectively control permeability and degradation properties utilizing specific external stimuli make capsules an exciting platform for a variety of controlled release applications. For examples, light-sensitive capsules would have applications in a variety of cosmetics formulations. However, most techniques for creating stimuli-responsive polymer capsules require extensive and complex synthesis techniques. Here, we present a quick and simple technique for the synthesis of photoresponsive biopolymer capsules. These photoresponsive biopolymer capsules are synthesized through an electrostatic interaction of a charged biopolymer and a UV-sensitive moiety, creating a robust crosslinked capsule shell. Upon exposure to UV irradiation the UV-sensitive moiety degrades into inert by-products which cannot interact with the biopolymer. As the UV-sensitive moiety degrades the capsule shell weakens, and eventually ruptures, releasing any payload contained within the capsule. Capsule strength and photodegradation time can easily be tuned by altering several parameters such as UV-sensitive molecule concentration, biopolymer molecular weight, and crosslinking time of the capsules. Through manipulation of these parameters we demonstrate these capsules can be utilized as novel vehicles for the controlled and extended release of a variety of payloads.
SM8.4: Poster Session I: Advanced Polymers
Session Chairs
Tuesday PM, April 18, 2017
Sheraton, Third Level, Phoenix Ballroom
9:00 PM - SM8.4.01
Synthesis and Characterization of Photo-Cleavable Nucleotides
Haikang Yang 1 , Anu Stella Mathews 1 , Carlo Montemagno 1
1 , University of Alberta, Edmonton, Alberta, Canada
Show AbstractThis work focuses on the synthesis and chatacterization of eight compounds of 3′-modified-2′-deoxy ribonucleoside triphosphates (dNTPs) for oligonucleiotide custom synthesis. These nucleotide analogues are modified by capping the 3′-OH by a photolabile protecting group which can temporarily cease DNA strand growth and can smoothly reinitiate the growth by photo cleavage of the protecting group and setting the 3′-OH of dNTPs free to propagate. 3′-O-(2-Nitrobenzyl)- 2′ deoxy ribonucleoside triphosphates (NB-dNTPs) and 3′-O-(4,5-Dimethoxy-2-Nitrobenzyl)- 2′ deoxy ribonucleoside triphosphates (DMNB-dNTPs) are the dNTPs synthesised using selective protection strategy. Structural confirmation of the compounds are done by NMR and MS. The UV-cleaving studies of these compounds are monitored and quantified by LC/MS and 1H NMR spectral traces. The synthesized nucleotides are employed for terminating and reinitiating templateless DNA synthesis, using primer indepentent Terminal Deoxynucleotidyl Transferase (TdT) enzyme. These nucleiotides modified at the 3′ hydroxyl position act as template indepentent enzyme mediated oligonucleiotide synthesis terminators, finding immense applications such as DNA synthesis, DNA and RNA 3′ end labelling, mechanistic probes, antimetabolites and antiviral agents paving a novel strategy towards the stacking of dNTPs with the potential to reinforce present technologies.
9:00 PM - SM8.4.02
Highly Specific In Vivo Gene Delivery for p53-Mediated Apoptosis and Genetic Photodynamic Therapies of Tumour
S. Ja Tseng 1
1 , Graduate Institute of Oncology, National Taiwan University College of Medicine, Taipei Taiwan
Show AbstractAnti-cancer therapies are often compromised by non-specific effects and challenged by tumour environments' inherent physico-chemical and biological characteristics. Often, therapeutic effect can be increased by addressing multiple parameters simultaneously. Here we report on exploiting extravasation due to inherent vascular leakiness for delivery of a pH sensitive polymer carrier. Tumours' acidic microenvironment instigates a charge reversal that promotes cellular internalization where endosomes destabilize and gene delivery is achieved. We assess our carrier with an aggressive non-small cell lung carcinoma (NSCLC) in-vivo model and achieve greater than 30% transfection efficiency via systemic delivery. Rejuvenation of the p53 apoptotic pathway as well as expression of KillerRed protein for sensitization in photodynamic therapy (PDT) is accomplished. A single administration greatly suppresses tumour growth and extends median animal survival from 28 days in control subjects to 68 days. The carrier has capacity for multiple payloads for greater therapeutic response where inter-individual variability can compromise efficacy.
9:00 PM - SM8.4.03
Exploring Relaxation Dynamics in Azobenzene Functionalized Polyimides Using Cantilever Bending Experiments and Finite Element Modeling
Matthew Smith 1 , Amir Skandani 2 , David Wang 3 , Loon-Seng Tan 4 , Timothy White 4 , M. Ravi Shankar 2
1 Department of Engineering, Hope College, Holland, Michigan, United States, 2 Department of Industrial Engineering, University of Pittsburgh, Pittsburgh, Pennsylvania, United States, 3 Biological and Nanoscale Technologies Division, UES Inc., Dayton, Ohio, United States, 4 Materials and Manufacturing Directorate, Air Force Research Laboratory, Dayton, Ohio, United States
Show AbstractPhotoisomerization of azobenzene functionalized polymers is a convenient route to transduce light into mechanical work and has been shown to hold promise for a versatile array of programmable materials systems. In particular, azobenzene functionalized polyimides (Azo-PIs) possess several advantages as actuator candidates including exceptional thermal stability, large out-of-plane deformations, and high mechanical strength and stiffness. Generally, the photo-induced deformations in these materials are not fully retained, exhibiting dynamic recovery over time when the light source is removed. In order to tailor Azo-PIs for remotely triggered, fine-tuned actuators and shape memory devices, it is critical to also understand and quantify their relaxation behavior after the light source has been removed. Though studies have investigated the dynamics of strain recovery in azobenzene functionalized polymers after irradiating with UV light, investigations of the relaxation dynamics in Azo-PIs associated with blue-green light remain scarce. Herein, we present results from cantilever bending and relaxation experiments for a series of linear and cross-linked Azo-PIs with varying backbone rigidities. We also use a finite element model that couples population dynamics to material strain to gain insight into the material structure-properties relationships. Ultimately, the goal of this work is to systematically study the strain relaxation dynamics of Azo-PIs after being irradiated by a blue laser (450 nm), and explore the effect of structural parameters - mainly rigidity of polymer backbone molecules - in the short timescale dynamics of polyimides. Control over the persistence and relaxation of photomechanical strains is critical to the broader utility of these materials in shape programmable systems such as those used in the priming of photomechanical actuators and morphing surfaces.
9:00 PM - SM8.4.04
Incorporating Longer Wavelength Azo Dyes in Polymer Networks for Photomechanical Applications
Brandon Derstine 1 , Sean Gitter 1 2 , Jessica Korte 2 , Matthew Smith 2 , Jason Gillmore 1
1 Department of Chemistry, Hope College, Holland, Michigan, United States, 2 Department of Engineering, Hope College, Holland, Michigan, United States
Show AbstractAzo dyes have long been incorporated into photomechanical systems with promise as wireless actuators.[1] Most azo dyes photoisomerize in the ultraviolet to blue/green region of the electromagnetic spectrum. However, these high energy wavelengths often lead to photodegradation of the material. They are also competitively absorbed by other device components. Furthermore, these wavelengths are incompatible with mammalian tissue, thus limiting any potential biomedical applications.
Recently, Aprahamian and coworkers published a series of BF2-coordinated azo dyes which photoisomerize in the red[2] to near-infrared[3] (NIR) region of the spectrum. These lower energy wavelengths minimize absorption by mammalian tissue, photodegradation of the material, and competitive absorption by other device components. In the Gillmore organic photochemistry research group, we are preparing analogs of Aprahamian’s dyes with polymerizable “handles” that may then be incorporated into photomechanical polymers. Meanwhile in the Smith research group in materials science / mechanical engineering, we are developing model polymer systems for the incorporation and characterization of azo dyes in constrained network environments.
Our efforts to date on both fronts and our future plans for this nascent research collaboration are described in this poster.
[1] White, T.J.; Broer, D.J. Nat. Mater. 2015, 14, 1087-1098.
[2] Yang, Y.; Hughes, P.; Aprahamian, I. J. Am. Chem. Soc. 2012, 134, 15221-15224.
[3] Yang, Y.; Hughes, P.; Aprahamian, I. J. Am. Chem. Soc. 2014, 136, 13190-13193.
9:00 PM - SM8.4.05
Continuous Fabrication of Polymeric Microstencil by Using Dewetting Phenomenon
Moonkyu Kwak 1 , Cheol Woo Park 1 , Gyu Man Kim 1 , Jung Goo Hong 1
1 , Kyungpook National University, Daegu Korea (the Republic of)
Show AbstractWe present the continuous fabrication of a polymeric microstencil by using continuously occurring dewetting phenomenon via roll to roll imprinting equipment. To realize dewetting assisted residual free imprinting, mold material, polymer resin and substrate were selected by using interfacial surface energy analysis. In addition, optimal parameters of the continuous process are also explored by systematical investigating the completion of microstencil depending on the process speed, aspect ratio of mold and applied pressure. In the result, the polymeric microstencil was produced continuously with very high yield and its maximum resolution reached to 20 μm in diameter. For the easy continuous demolding during the roll to roll process, the substrate was further chosen with paraffin-coated film (PPF) which has low enough surface energy for dewetting but still has a higher adhesion value than PDMS mold. This versatile, high-throughput microstencil architecturing may be applicable to many applications requiring flexibility, scalability, and specific material, and their commercially-feasible production.
9:00 PM - SM8.4.06
4D Printing Bio Functional Materials
Anu Stella Mathews 1 , Surjith Kumaran 1 , Jiaxin Fan 1 , Sinoj Abraham 1 , Carlo Montemagno 1
1 , University of Alberta, Edmonton, Alberta, Canada
Show AbstractThe transfer of bio functionality from native living organisms to stable engineered environment opens a wide horizon of applications. Our work focus on the creation of materials and devices that transform bio traits and collect, process and act on the information in response to changes in their local environment thus promoting additive manufacturing from 3D space to a four-dimensional, functional space. Through developments in stabilizing fundamental biological building blocks and integral membrane proteins, the suite of tools available to engineer complex systems has been greatly expanded. In this work a new class of light curable bio inks exploits this expanded set of tools to enable the incorporation of biological function as an intrinsic property in the devices we print. This device incorporates bio functions into a new class of engineered structures with high efficiency and purity. We have designed and developed protocol for synthesizing and stabilizing biological molecules out of their living environment, and transferring into 4D printable bioinks. The designed printable bio-inks process the potential of precise heterogeneous assembly attained through the selection of polymers, bio functional moieties and light source. The properties of this 4D printable bioinks are tailored according to the functionality incorporated and the light source used so that the materials can be utilized for fabricating 4D printed systems with potential applications varying from biochemical energy harvesting devices to scaffolds for biomedical engineering.
9:00 PM - SM8.4.07
Advancing the Knowledge on the Structural Properties of the Biocompatible and Biodegradable Electroactive Eumelanin Polymer
Dominic Boisvert 1 , Carmela Prontera 3 2 , Sebastien Francoeur 1 , Antonella Badia 1 , Clara Santato 1
1 , Polytechnique Montréal, Montreal, Quebec, Canada, 3 , Enea Research Center, Roma Italy, 2 , University of Naples Federico II, Napoli Italy
Show AbstractEumelanin is a dark-brown biopigment largely present in animals and plants. This biopolymer results from the polymerization of two monomers (building blocks), namely 5,6-dihydroxyindole (DHI) and 5,6-dihydroxyindole-2- carboxylic acid (DHICA) [1]. Important physicochemical properties of eumelanin include metal chelation, photoprotection (the pigment absorbs in the nearIR – UV region of the spectrum) and mixed ionic-electronic conduction. It also features biocompatibility and biodegradability [2]. Although eumelanin has been studied for a few decades now, the nature of its chromophoric units and the mechanism of charge carrier transport are still largely undiscovered, mainly because of the chemical disorder that characterizes natural eumelanin. Obtaining a good control over the molecular and supramolecular structures of the pigment is therefore imperative to achieve better understanding of those properties, a key to demonstrate eumelanin-based environmentally and human-friendly technologies.
Here we report on the controlled polymerization in films of DHI building blocks spin coated on SiO2 and quartz substrates, observed in situ by Atomic Force Microscopy (AFM). DHI films obtained from methanol solutions of freshly synthesized DHI, were polymerized in ambient conditions (oxidative polymerization). A number of factors likely contribute to establishing the mechanism of polymerization. Besides molecular oxygen, monomer/oligomer aggregates in the methanol suspensions can act as nuclei of the polymerization. Our preliminary results suggest that the physical contact between the AFM tip and the monomers/oligomers plays a role in triggering the polymerization. Once started, the polymerization front develops within a time scale of minutes on a preferential direction, creating elongated, dendritic structures, leading to furrow-like surfaces, separated by a few micrometers. The dendrimers, carefully characterized by AFM, were also investigated by spatially resolved absorption spectroscopy. The large scale, directional and dendritic polymerization can be exploited to obtain chemically controlled eumelanin samples that can be efficiently characterized for their optical and transport properties and, on the long term, exploited in organic electronics devices, such as transistors and solar cells. Further studies on the polymerization in the presence of metallic substrates or metal ions will provide insight on the effect of metal chelation on the polymerization patterns, thus giving more insight for future melanin-based devices.
[1]
M. D'Ischia, et. al., "Melanins and melanogenesis: methods, standards, protocols," Pigment Cell & Melanoma Research, vol. 26, no. 5, pp. 616-633, 2013.
[2]
C. J. Bettinger, et. al., "Biocompatibility of biodegradable semiconducting melanin films for nerve tissue engineering," Biomaterials, vol. 30, no. 17, pp. 3050-3057, 2009.
9:00 PM - SM8.4.08
Fluorescent Potassium Ion Sensors
Yanqing Tian 1
1 Department of Materials Science and Engineering, South University of Science and Technology of China, Shenzhen, Guangdong, China
Show AbstractPotassium ions which make up about 0.4% of the mass in the human body and are the most abundant intracellular cation, play diverse roles in biological processes including muscle contraction, heartbeat, nerve transmissions, and kidney functions. Abnormal K+ fluctuations are early indicators of diseases such as alcoholism, anorexia, bulimia, heart disease, diabetes, AIDS, and cancer. Therefore the detection of K+ in physiological environment is of great significance. One of the earliest and best-known intracellular fluorescent K+ probes is potassium-binding benzofuran isophthalate (PBFI), which uses a diaz-18-crown-6 as a ligand and a benzofuran derivative as the fluorophore. Unfortunately PBFI, suffers poor selectivity for potassium ions with respect to sodium ions (Na+). Herein, we will describe our results for developing highly selective potassium ion sensors. We used triazacryptand (TAC) as a high selective potassium ion ligand and various fluorophores for preparing highly selective potassium molecular and planar polymeric probes. We constructed a potassium ion sensor using a 2-dicyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran (TCF) as a strong electron withdrawing group and the TAC as the electron donating group for the first intracellular potassium ion sensor. Later we incorporated a triphenylphosphonium (TPP) unit into a BODIPY fluorophore with TAC as the ligand for the first mitochondrial targeting potassium ion probe. These two molecular probes show high selectivity for potassium ions and capable for monitoring intracellular potassium fluxes. Especially the probe with TPP moiety showed high co-localization efficiency for mitochondria. We also prepared a polymerizable potassium ion probe using naphthalimide as the fluorophore for generation of planar thin film-based potassium ion sensors. These polymeric sensors showed potassium ion dynamic response ranges from 1 to 20 mM, indicating its suitableness for extracellular sensing. This sensor also has a minimum influence by pH from 6 to 8, showing its suitableness for biostudies. We tested whether this sensor can be used to monitor extracellular potassium ion concentration changes. We used lysozyme to kill bacteria (E. Coli and B. Subtilis) to release their cellular potassium ions to the media to enable us to monitor potassium concentration changes in real time. Results showed that potassium ion concentration is higher with higher cell densities. We also found the difference among the two species of cells. E coli release potassium ions much slower than that Subtilis did. Thus in this presentation, we will give detailed results about our potassium ion sensors.
9:00 PM - SM8.4.09
Nanodiamond-Embedded Polymeric Thermogels and Hydrogels—Properties and Applications
Kangyi Zhang 1 , Sing Shy Liow 1 , Zhi Wei Low 1 , Anis Abdul Karim 1 , Xian Jun Loh 1 2 3
1 , Institute of Materials Research and Engineering, Singapore Singapore, 2 Materials Science and Engineering, National University of Singapore, Singapore Singapore, 3 , Singapore Eye Research Institute, Singapore Singapore
Show AbstractNanodiamonds (NDs) have emerged as an attractive candidate for biomedical applications such as imaging and drug delivery. Clinical relevance has been shown in many recent studies such as for therapeutic contact lenses, implantable drug-eluting hydrogels and anti-bacterial tooth fillings. NDs are highly biocompatible and amenable to surface modifications for different purposes. Nanodiamonds have previously been shown to enable targeted delivery of chemotherapeutics and the stable delivery of hydrophobic drugs and genetic material. Beyond drug delivery, nanodiamonds can also act as nanofillers to strengthen hydrogels for structural support. The mechanical properties are highly tunable and the improved strength makes them attractive for different tissue engineering scaffolds.
Our lab has previously developed polyurethane-based thermogels which can be used for healthcare and personal care applications. Our polyurethane thermogel is capable of gel formation at low polymeric concentrations and allows for reversible sol-gel transitions. Compared to poly(N-isopropylacrylamide) (PNIPAAm) systems, our thermogel is biodegradable and will not require any surgery to remove the gel after utilization. Delivery of active ingredients can be done in a single injection and the in situ gelation will enable a localized and sustained drug delivery.
After nanodiamond incorporation into the thermogels, reversible sol-gel transition was unaffected. Our system retained high encapsulation efficiency of both hydrophobic and hydrophilic actives. We studied this gelation phenomenon over various concentrations of NDs. Rheology and other characterization will be discussed. Cell biocompatibility tests will also be presented to show the biological feasibility of this system. We envision this biocompatible and biodegradable system to be highly versatile in delivering therapeutics with high efficiency. A range of healthcare and personal care applications can be explored.
9:00 PM - SM8.4.10
Controlling the Pore Size of Mesoporous Carbon Thin Films through Thermal and Solvent Annealing
Guoliang Liu 1 , Zhengping Zhou 1
1 , Virginia Polytechnic Institute and State University, Blacksburg, Virginia, United States
Show AbstractWe describe an approach to controlling the pore size of mesoporous carbon thin films from metal-free polyacrylonitrile-containing block copolymers. A high-molecular-weight poly(acrylonitrile-block-methyl methacrylate) (PAN-b-PMMA) was synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. We systematically investigated the self-assembly behavior of PAN-b-PMMA thin films during thermal and solvent annealing, as well as the pore size of mesoporous carbon thin films after pyrolysis. The as-spin-coated PAN-b-PMMA microphase-separated into uniformly spaced globular nanostructures, and these globular nanostructures evolved into various morphologies after thermal or solvent annealing. Surprisingly, through thermal annealing and subsequent pyrolysis of PAN-b-PMMA into mesoporous carbon thin films, the pore size and the center-to-center spacing of pores increased significantly with annealing temperature, different from most block copolymers. In addition, the choice of solvent during solvent annealing strongly influenced the block copolymer nanostructures and the pore size of mesoporous carbon thin films. The discoveries herein provide a simple strategy to control the pore size of mesoporous carbon thin films by tuning thermal or solvent annealing conditions, instead of synthesizing a series of block copolymers of various molecular weights and compositions.
9:00 PM - SM8.4.11
Long-Range Ionic Conductivity of Saturated Bacterial Cellulose-Based Solid Biopolymer Electrolyte Offers Insights into the Transport Mechanism of Bulk Nanofibers
Robert Ccorahua 1 , Omar Troncoso 1 , Fernando Torres 1
1 , Pontificia Universidad Catolica del Peru, LIMA Peru
Show AbstractThe study of electrically conductive bionanocomposites has attracted scientific interest due to the increasing demand of new technologies for the development of bioelectronic devices such as biointerface materials and biosensors. In this context, bacterial cellulose nanofibers (BC) appears as a promising supporting material for conductive additives due to its high strength and stiffness, renewability, biocompatibility and biodegradability.
Complexed bacterial cellulose-potassium iodide (BC-KI) films were prepared by dipping BC films in solutions of KI at different concentrations. Impedance spectroscopy tests were carried out and the imaginary part of the electric modulus (M’’), impedance (Z’’) and dielectric loss (ε’’) were plotted as functions of frequency (f). The dielectric data were also utilized to calculate the coefficient of ionic diffusivity using a model proposed by Bandara & Mellander.
The results showed that the highest ionic conductivity (1x10-5 S/cm) was achieved for the specimens with the highest KI content (BC-KI 91%). In addition, the analysis of the M’’ and ε’’ spectra suggests that the dielectric response of the material is mainly due to delocalized (long-range conductivity) ion motion. A single peak in the M’’ spectra suggests that the ionic and polymer segmental motion is strongly coupled. In addition, the increase on the salt content promoted the long-range random hopping movement of ions, even at high frequencies (1 MHz). The high coefficient of ionic diffusivity (8.01 x 10-3 cm2/s) of the BC-KI samples with content of 89% of KI would be due to the large surface area of BC nanofibers.
In conclusion, the high conductivity, dominated by long-range random hopping ion motion, and high diffusion coefficient of saturated BC could open new windows for its use in solid energy and biointerface devices.
9:00 PM - SM8.4.12
Ultrasonic Cavitation Induced Shape-Memory Effect in Porous Polymer Networks
Pengfei Zhang 1 2 3 , Marc Behl 1 3 , Xingzhou Peng 1 2 3 , Muhammad Yasar Razzaq 1 , Andreas Lendlein 1 2 3
1 , Institute of Biomaterial Science and Berlin-Brandenburg Centre for Regenerative Therapies, Helmholtz-Zentrum Geesthacht, Teltow Germany, 2 , Institute of Chemistry, University Potsdam, Potsdam Germany, 3 , Tianjin University-Helmholtz-Zentrum Geesthacht Joint Laboratory for Biomaterials and Regenerative Medicine, Teltow Germany
Show AbstractUltrasound is an efficient tool to generate local mechanical force in liquid media by cavitation.[1,2] The application of cavitation-based mechanical forces (CMF) has evolved as a valuable technology to increase the skin permeability, or to enhance the drug delivery efficiency to targeted tissues. Inspired by the usage of CMF in natural soft materials and the demand to implement other stimuli than heat into shape-memory polymers, we explored whether a polymer network can be created, which is capable to change its shape when CMF are applied. As the ultrasonic cavitation occurs dominantly at the surface of solid polymers, a key challenge was the design of an appropriate material structure, which enables the CMF to effectively permeate throughout the bulk polymer sample. In addition, the selection of suitable molecular switches (temporary crosslinks) was a critical issue as well. The molecular switches must exhibit mechano-responsivity to enable the shape recovery during sonication but also need to provide a certain stability for fixing the temporary shape. We addressed these challenges by the design of a rhodium-phosphine interconnected macro-porous polymer network (Rh-IMP).[3] To synthesize Rh-IMP, n-butyl acrylate and diphenylphosphinostyrene (DPPST) were copolymerized in the presence of poly(propylene glycol) dimethacrylate crosslinker. Here, poly(n-butyl acrylate) was employed as the compound for the elastic polymer backbone, while DPPST was helpful to establish rhodium-phosphine coordination bonds by the addition of [RhCl(COD)]2. The rhodium-phosphine coordination bonds (Rh-PCBs) and their separated micro-phases act as temporary crosslinks in Rh-IMP. Rheology measurements indicated a decrease in storage moduli (G′) of the Rh-IMP, originally ranging from 62 to100 kPa to 30-58 kPa after sonication (US, f =20 kHz). After removal of US, the values of G′ displayed a reversible increase and reached equilibrium after 6 hours, thus verifying the reversible dissociation of the aggregates of the micro-phase separated morphology in Rh-IMP. In this way, the ligand exchange of Rh-PCBs in the polymer network is accelerated, resulting in a topological rearrangement of molecular switches. This rearrangement of molecular switches enables the Rh-IMP with a CMF-induced shape-memory effect with the shape-fixity ratio in a range from 43 to 93% and shape-recovery ratio ranging from 43 to 97% for samples differing in DPPST mole ratios. The interconnected macro-porous structure with thin pore walls is essential for allowing the CMF to effectively permeate throughout the polymer network. Potential applications of this CMF-induced shape-memory polymer could be mechano-sensors or ultrasound controlled switches.
References
[1] D. G. Shchukin, E. Skorb, V. Belova, H. Mohwald, Adv. Mater. 2011, 23, 1922.
[2] S. Mitragotri, D. Blankschtein, R. Langer, Science 1995, 269, 850.
[3] P. Zhang, M. Behl, X. Peng, M. Razzaq, A. Lendlein, Macromol. Rapid Commun. DOI: marc.201600439R1.
9:00 PM - SM8.4.13
Surface Functionalization and Finishing of 3D Printed Objects with Inkjet Printing and Nanoimprint Lithography
Anita Fuchsbauer 1 , Michael Muehlberger 1 , Helene Ausserhuber 1 , Michael Haslinger 1 , Thomas Lederer 1
1 , Profactor GmbH, Steyr-Gleink Austria
Show AbstractAdditive manufacturing [1] is a term that sums up different technologies that all have in common that the object to be built is generated in a layer-by-layer fashion making it possible to create objects with high geometrical complexity. Furthermore, each fabricated object can be different from the previous one. In order to apply functionalization and surface finishing on top of such objects technologies are needed that can cope with different and varying topologies. Inkjet printing seems to be especially favorable here as it allows the contact free deposition of different types of materials at an exact position onto substrate and can thus be used to create micro- and macrostructures. Inkjet printing is by far not limited to graphical paper printing [2] any more, but is used in printed electronics (like PCB [3], solar cells [4], …), display printing (e.g. PLED [5]) and several other areas. Additional functionalities can be obtained by Nanoimprint Lithography (NIL), especially if the imprint material is inkjet printed and the stamp is flexible. In order to combine AM, inkjet printing and NIL two major topics have to be addressed: (a) inkjet inks with suitable formulations for NIL and (b) inkjet printing on substrates with different topologies. In order to develop inkjet inks suitable for multilayer printing as well as for NIL different commercial available materials from micro resist technology GmbH [6] were investigated and further adapted. Parameters like printhead – substrate distance were investigated and found essential in this field. Further challenges in this field are coping with rough 3D printed surfaces, finding the right spot on the 3D-printed object and adjusting the printhead-substrate distance above a complex surface. We will show possibilities and concepts how to address those issues, using flexible stamps to perform NIL on 3D printed objects, inkjet printing to apply the imprint material on the right spot and 3D machine vision in combination with robotics to position the printhead above the 3D-printed surface
The authors acknowledge funding from Austrian Ministry for Transport, Innovation and Technology (bmvit, ANIIPF project) and the Austrian Research Promotion Agency (FFG, Addmanu project) Furthermore, this work partly funded by the FTI project “ProTechLab”(funded by means of the strategic economy and funding program “Innovatives OÖ2020”)
[1] Guo, N., et al., Front. Mech. Eng. 8 (2013), 215.
[2] C. Williams, Phys. World, 19 (2006) 24–29
[3] C.-W. Wang, W.-C. Chen, K. Cheng, L. Yuh-Zheng, International Conference on Digital Printing Technologies, Portland, (2007), 855–858.
[4] A. Fuchsbauer, J. Kastner, B. Unterauer, M. Wagner, F. Tomarchio, N. Decorde, A. Ferrari, I. Gnatiuk, D. Holzinger, MRS Fall Meeting 2015, BB6.01
[5] F. Dijksman, P. C. Duineveld, M. J. J. Hack, A. Pierik, J. Rensen, J.-E. Rubingh, I. Schram, and M. M. Vernhout, J Mater Chem, 17 (2007), 511 – 522
[6] http://www.microresist.de/
9:00 PM - SM8.4.14
Super Stretchable Gas Barrier of Hydrogen-Bonded Multilayer Nanobrick Wall Thin Films
Shuang Qin 1 , Yixuan Song 1 , Michael Floto 1 , Jaime Grunlan 1
1 , Texas A&M University, College Station, Texas, United States
Show AbstractPackaging of food, pharmaceuticals and electronics often requires gas barrier layers to protect against oxidative degradation. In many cases, during processing or use, the packaging can be subjected to significant strain, so stretchable gas barrier coatings that can maintain high barrier are highly desirable. Layer-by-layer deposition of polymer/clay thin films from water has been shown to produce ‘super’ gas barrier layers, with permeability lower than inorganic oxide or metalized thin films, but these films often crack when stretched more than 5%. Hydrogen-bonded multilayer assemblies, such as poly (ethylene oxide) (PEO)/poly (acrylic acid) (PAA), exhibit high stretchability, but have much higher oxygen permeability (yielding only a 10X barrier improvement on 1.6 mm natural rubber). Here we show how montmorillonite (MMT) clay platelets were incorporated into the PAA solution to prepare PEO/PAA+MMT multilayer thin films. Highly aligned platelets are observed in these films and improved the oxygen transmission rate (OTR) by a factor of 10 relative to PEO/PAA previously reported (when deposited on a 1mm thick polyurethane rubber). A 10-bilayer (432 nm thick) PEO/PAA+MMT film has an OTR (1.74 cc /m2*day*atm) that is two orders of magnitude lower than the polyurethane rubber substrate. When multiplied by thickness, the calculated coating permeability is 1.5*10-15 cm3*cm/ (cm2*Pa*s), which is five orders of magnitude lower than the substrate. This film maintains its inherit stretchability from PEO/PAA and maintains its high barrier at 20% strain. This is the best stretchable gas barrier ever reported, making these films ideal for applications such as pressurized devices that use elastomeric components.
9:00 PM - SM8.4.15
Highly Stretchable Electrical Conductive Composites Fabricated from Conducting Polymer Networks and Silver Nanostructures for Wearable Electronics
Bo Song 1 , Kyoung-sik Moon 1 , CP Wong 1
1 , Georgia Institute of Technology, Atlanta, Georgia, United States
Show AbstractFuture wearable and portable electronic devices have promoted the research for novel stretchable electrically conductive composites (SECC) in advanced interconnect technology. Currently, challenges remain for the practical application of SECC, including the requirements for ultra-low resistivity (~10-5 Ω cm) for faster operation, the sufficient stretchability to withstand strains for human’s movement (~55%), and retaining electrical properties after mechanical cycles. New materials designs via the shape engineering of conductive fillers and tuning the polymer matrix provide feasible solutions to address the technical challenges.
Here we report a novel approach to fabricate polyurethane (PU)-based SECC by incorporating binary silver-based conductive fillers into a conductive polymer engineered elastomer matrix. The engineering of the conductive polymer resins includes the synthesis of PU elastomer and embedding PU-compatible conductive polymers. The synthesized PU delivered very high mechanical strains over 1000% with small hysteresis. The PU also showed a large volume shrinkage during curing process and soft segments containing polyols can efficiently reduce the organic surfactant on Ag, providing a resistivity 20 times lower than that of PDMS-based SECC. The conductive polymer used, polyaniline (PANI), takes advantage of the acid doping chemistry to control the electrical conductivity, free-volume, and solubility. In contrast to the bulk PANI particles, the nanostructured PANI fibers (~60 nm in diameter, 1-2 µm in length) were synthesized via interfacial polymerization with higher surface area and greater sensitivity towards electrical/mechanical signals. The camphorsulfonic acid was chosen as the dopant to improve the counter ion induced processibility of the PANI, making it highly compatible with the swelled PU in solution. The PU/PANI hybrid matrix has achieved a percolation threshold with less than 10 wt% of PANI loading, while maintaining good stretchability.
Regarding the filler engineering, the 1D silver nanowires (Ag-NWs) and 2D silver microflakes (Ag-MFs) were used as the binary filler systems. Due to the higher aspect ratio, the Ag-NWs can be electrically conductive at a relatively lower percolation threshold in a polymer matrix. To prepare the Ag-NWs, the polyol process was employed using poly(vinylpyrrolidone) as the capping agent and ethylene glycol as the solvent at low temperature (130°C). The synthesized Ag-NWs had an average diameter of 200 nm and the length of 30-40 µm. When using with the silver Ag-MFs, the Ag-NWs could efficiently bridge the flakes and create more conductive channels. The SECC consisting PU/PANI matrix and binary Ag fillers achieved ultra-low resistivity of 1×10-4 Ω cm at 50 wt% of filler loading. In particular, the incorporation of conductive elements in the polymer matrix and the use of high aspect-ratio Ag-NWs (~200) greatly improved the electrical performance under and after the mechanical strains.
9:00 PM - SM8.4.16
Matrix Regenerative Polymer Nanoparticles to Improve the Tumor Microenvironment in Non-Small Cell Lung Cancer
Dhruv Seshadri 1 2 , Andrew Shao 1 2 , Anand Ramamurthi 2 3
1 Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, United States, 2 Lerner Research Institute, Department of Biomedical Engineering, Cleveland Clinic, Cleveland, Ohio, United States, 3 Department of Molecular Medicine, Cleveland Clinic Lerner College of Medicine of Case Western Reserve University, Cleveland, Ohio, United States
Show AbstractNon-small cell lung cancers (NSCLCs) are a leading cause of mortality in the Unites States with >66% of patients at an advanced stage with a 15% survival rate. Cytotoxic treatments are ineffective due to genetic alterations in tumor suppressor genes. New immune-checkpoint inhibitors targeting the PD1/PD-L1 pathway are promising to treat NSCLCs but response rates are poor (15-20%), motivating need for adjuvant approaches. This has been attributed to the Tumor Micro Environment (TME) which favors immune evasion and pro-tumorigenic pathways such as macrophage polarization from a pro-inflammatory (M1) type to an immunosuppressive and pro-tumorigenic (M2) phenotype. In > 90% of NSCLC patients, the TME is also compromised by secondary COPD, with chronic breakdown of alveolar elastic structures to generate elastin peptides (ELPs), which in turn promote macrophage polarization to the M2 phenotype. Preventing elastolysis and stimulating elastic fiber regenerative repair can thus benefit anti PD1/PDL1 therapy outcomes. This is however severely challenged by inherently poor elastogenicity of adult cells. In this work, we have thus investigated a multipronged approach to NSCLC therapy based on tumor-localized nanoparticle (NP)-based release of doxycycline, which has been shown to inhibit M1 to M2 phenotypic switch and which we have determined to have both anti-proteolytic and pro-elastogenic effects in the 10-20 μM dose range. The biodegradable poly(ethylene glycol)-poly(lactic glycolic acid) (PEG-PLGA) NPs were surface functionalized with a cationic amphiphile. The size of our NPs (200-300 nm) prevented their ready clearence by the RES and ensured minimal phagocytosis. Steady state release of DOX from the NPs depended on DOX loading and NP concentration, but was in the useful low micromolar dose range; at 20 days, only ~28% of theoretically loaded DOX had been released. The cationic amphiphiles on the NPs augmented the effects of the released drug in reducing ELP generation via protease inhibition, and stimulating elastin precursor synthesis and crosslinking. Pendant IL4-receptor (IL4R) antibodies on the NP surface enabled targeted binding to IL4R-expressing M1 macrophages and blocked IL4-induced polarization. In ongoing work, we are investigating in cell culture models, utility of the NPs in inhibiting M1 to M2 phenotypic switch of alveolar macrophages and efficacy of targeting our IL4R Ab-modified NPs to the tumor microenvironment in a C57BL6 mouse tumor model
9:00 PM - SM8.4.17
Cyclodextrin Stabilised Emulsions, Cyclodextrinosomes and Cyborg Cells
Baghali Mathapa 1 , Vesselin Paunov 1
1 School of Mathematics and Physical Sciences (Chemistry), University of Hull, Hull United Kingdom
Show AbstractWe explored the self-assembly of cyclodextrins (CDs) at the oil-water interface through the formation of inclusion complexes (ICs) with the oil and further assemble into microcrystals at the oil-water interface [1-4]. We demonstrate the spontaneous formation of a dense layer of adsorbed CD-tetradecane IC microcrystals at the tetradecane-water interface whose morphology and size are dependent on the type of CD and oil used. At large oil volume fractions, this phenomenon led to the formation of a Pickering type of oil-in-water emulsion stabilised by adsorbed CD-oil microcrystals while at low oil volume fractions it completely solubilises the oil in the form of IC microcrystals. We also report the preparation of o/w emulsions stabilised by microcrystals of cyclodextrin-oil inclusion complexes. The inclusion complexes are formed by threading cyclodextrins from the aqueous phase on n-tetradecane or silicone oil molecules from the emulsion drop surface which grow further into microrods and micro-platelets depending on the type of cyclodextrin. These microcrystals remain attached at the surface of the emulsion drops and form densely packed layers. The novelty in this emulsion stabilisation mechanism is that molecularly dissolved cyclodextrin from the continuous aqueous phase is assembled into colloid particles directly onto the emulsion drop surface, i.e. molecular adsorption leads to effective Pickering stabilisation. The β-CD stabilised tetradecane-in-water emulsions were so stable that we used them as templates for preparation of cyclodextrinosomes after the removal of the core oil (Fig. 1). We also report the preparation of CD-stabilized emulsions with a range of other oils and studied the effect of the salt concentration in the aqueous phase, the type of CD and the oil volume fraction on the type of emulsion formed. The CD-stabilized emulsions and cyclodextrinosomes can find applications in a range of surfactant-free formulations in cosmetics, home and personal care, and in pharmaceutical formulations as drug delivery vehicles. We describe two alternative methods for surface functionalisation of living cells with cyclodextrin molecules without affecting the cell viability [5]. Living cells functionalised with CDs may find many potential applications as they can be loaded with drugs, immunosuppressants and other molecules forming inclusion complexes with their cyclodextrin interface.
[1] B.G Mathapa, V.N. Paunov, J. Mater. Chem. A, 2013, 1, 10836.
[2] B.G Mathapa, V.N. Paunov, PCCP, 2013, 15, 17903.
[3] B.G Mathapa, V.N. Paunov, Soft Matter, 2013, 9, 4780.
[4] B.G Mathapa, V.N. Paunov, J. Mater. Chem. B, 2013, 1, 3588.
[5] B.G Mathapa, V.N. Paunov, Biomaterialce Sci., 2014, 2, 212.
9:00 PM - SM8.4.18
Laser Direct-Write Fabrication of Core-Shell Microspheres
Benjamin Vinson 1 , Samuel Sklare 2 , Jayant Saksena 3 , Douglas Chrisey 2
1 Bioinnovation Program, Tulane University, New Orleans, Louisiana, United States, 2 Physics and Engineering Physics, Tulane University, New Orleans, Louisiana, United States, 3 Biomedical Engineering, Tulane University, New Orleans, Louisiana, United States
Show Abstract
Hydrogel microspheres have found extensive application in tissue engineering and drug delivery for their ability to encapsulate, culture, and/or transport cells, drugs, and other materials in a facile manner. In particular, core-shell microspheres with controlled ECM internal compartments allow for efficient, scalable, and customizable 3D cell culture. However, traditional microsphere fabrication methods provide limited control of core-shell microsphere size and spatial placement. High levels of spatial specificity, reproducibility, and viability have been previously reported using laser direct write (LDW) to print both cells and microspheres. Thus, to overcome these limitations, we show size and spatial control of core-shell alginate microspheres by using the LDW fabrication technique. Our findings show that sphere size is controllable within 10%, and fabricated microbeads can remain immobilized within 5% of their target placement. Demonstration of this technique using the human breast cancer cell line, MDA-MB-231, shows that cells encapsulated within either layer survive at a rate of >85%. Herein we demonstrate LDW’s ability to fabricate and systematically deposit core-shell microspheres into spatially-ordered patterns, with single-microsphere resolution.
9:00 PM - SM8.4.19
Target-Specific Therapeutic Cell Delivery Systems Using Hyaluronic Acid Derivatives
Yun Seop Kim 1 , Sei Kwang Hahn 1
1 Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang Korea (the Republic of)
Show AbstractHyaluronic acid (HA) is a biodegradable, biocompatible, non-immunogenic, ubiquitous, and naturally occurring linear polysaccharide. There are many kinds of HA receptors in the body, which have been exploited as target sites for HA-based drug delivery systems. Especially, hyaluronan receptor for endocytosis (HARE) and cluster of differentiation 44 (CD44) exist abundantly on liver and tumor, respectively. Mesenchymal stem cells (MSCs) have been widely explored for innovative cell therapies due to their ability to differentiate into diverse lineages and secrete a variety of favorable cytokines. However, migration of MSCs to the target site in most MSC therapies depends on the innate characteristics of MSCs such as the homing ligands of MSCs, resulting in long delivery time and low therapeutic efficacy. Here, we exploited HA for the target-specific delivery of therapeutic MSCs. We conjugated N-terminal amine group of wheat germ agglutinin (WGA) to aldehyde-modified HA for the surface modification of MSCs. WGA is a protein which can specifically recognize sialic acid and N-acetyl-D-glucosamine. The successful synthesis of HA-WGA conjugate was confirmed by gel permeation chromatography, circular dichroism, and Bradford assay. The cytotoxicity of HA-WGA conjugate and the incorporation of HA-WGA conjugate into the cellular membrane of MSCs were assessed by MTT assay and confocal microscopy. After surface modification of MSCs with HA-WGA conjugate, the bio-distribution of MSCs/HA-WGA conjugates after MSCs administrations through various routes was investigated via an IVIS® imaging system and a fluorescence microscope. We will discuss the feasibility of the target-specific MSC therapy for the treatment of liver diseases and cancers.
9:00 PM - SM8.4.20
Nanomechanical Behavior of Clay and Graphene Reinforced Polymers Multilayers
Mohammad Humood 1 , Shuang Qin 1 , Yixuan Song 1 , Jaime Grunlan 1 , Andreas Polycarpou 1
1 , Texas A&M, College Station, Texas, United States
Show AbstractPolymer nanocomposites are useful for many applications such as food packaging and flexible electronics due to their unique characteristics. These hybrid materials usually consist of a polymer matrix and reinforcement (e.g. clay or graphene oxide). Multilayer thin films were synthesized using the layer-by-layer (LbL) assembly method with different layer arrangements, thickness and composition. The simplicity and versatility of the LbL assembly method is due to its flexible water-based process. For packaging, durability is an important feature for these multilayer films, which requires resistance to abrasion in order to maintain the films’ functionality. Some applications are operated by means of mechanical contact such as touch screens and flat panel displays. In order to evaluate the mechanical properties, low and high load nanoindentation, and low and high load scratch experiments were performed. Clay and graphene based multilayers respond differently to applied load. Clay based multilayers, such as montmorillonite (MMT) and polyethylenimine (PEI) bilayers, have exceptional mechanical behavior and scratch resistance. These coatings exhibit high hardness and reduced elastic modulus, smooth surface and low friction. Graphene based multilayers show strong mechanical properties and effective load transfer in the normal direction, but these films show lower resistance to lateral forces compared to polymer/clay assemblies. The graphene/polymer multilayer films suffer from higher friction coefficient, more visible/wider scratches and lower elastic recovery. To improve the scratch resistance of these films, two extra processing steps were introduced: graphene oxide conversion to graphene and polymer crosslinking. These steps improved scratch resistance.
Symposium Organizers
Andreas Lendlein, Helmholtz-Zentrum Geesthacht
Kevin Cavicchi, University of Akron
LaShanda Korley, Case Western Reserve University
Bernd Rehm, Massey University
Symposium Support
MedShape, Inc.
MilliporeSigma
SM8.5/NM10.4: Joint Session: Functional Materials for Cellular and Biotechnological Applications
Session Chairs
Xiaodong Chen
Jianping Fu
Andreas Lendlein
Wednesday AM, April 19, 2017
PCC West, 100 Level, Room 102 AB
9:30 AM - SM8.5.01/NM10.01
Regulation of Mesenchymal Stem Cell Behavior and Secretion via Microscale Surface Roughness
Nan Ma 1 , Xun Xu 1 , Weiwei Wang 1 , Zhengdong Li 1 , Jie Zou 1 , Karl Kratz 1 , Andreas Lendlein 1
1 , Institute of Biomaterial Science and Berlin-Brandenburg Center for Regenerative Therapies, Helmholtz-Zentrum Geesthacht, Teltow Germany
Show AbstractMesenchymal stem cells (MSCs) are capable of differentiating into multiple lineages for cell-based regenerative therapies. Recent developments in biomaterials have indicated that the physicochemical natures of materials strongly influence self-renewal, differentiation and secretome profile of MSCs [1-2]. As a complement to traditional biochemical methods, there is a great promise to use physical approach such as roughness to instruct the behavior and paracrine capacity of MSCs to optimize their therapeutic potential. Here, as a model system, both polystyrene and poly (ether imide) surfaces with three roughness levels were fabricated: R0 (smooth), R1 (with roughness level comparable to cell size) and R2 (with roughness level greater than cell size). To ensure that the cells were only in contact to the material itself, MSCs were cultured in closed polymer cups with distinct roughness on bottom surfaces, which were processed via injection molding [3]. In this study, despite a high cell viability was shown on all polymeric substrates, the apoptotic and senescent levels were highly modulated by roughness. The apoptotic level and the ratio of senescent MSCs on R1 were lower than those on smooth R0 surface. Moreover, the secretion of pro-angiogenic factors of MSCs on R1 was remarkably upregulated compared to R0 and R2 and the enhancement of those factors could be abolished via blockage of focal adhesion associated signaling pathway. In summary, the polymeric substrates with surface roughness R1 provide more superior surface environment for MSCs cultivation in respect to apoptosis, senescence and secretion. Therefore, roughness might be an important parameter to be considered for advanced biomaterial design.
References:
[1] Phillips JE, Petrie TA, Creighton FP, García AJ. Acta Biomater. 2010, 6, 12-20.
[2] Lee J, Abdeen AA, Zhang D, Kilian KA. Biomaterials. 2013, 34, 8140-8148.
[3] B. Hiebl, K. Lutzow, M. Lange, F. Jung, B. Seifert, F. Klein, T. Weigel, K. Kratz and A. Lendlein. J Biotechnol. 2010, 148, 76-82.
9:45 AM - SM8.5.02/NM10.02
Fabrication of Crosslinked Sphere Structure of Biodegradable Polymer Nanoparticles for Efficient Controlled Drug Release
Ravichandran Honnavally Kollarigowda 1 , Anu Stella Mathews 1 , Sinoj Abraham 1 , Carlo Montemagno 1
1 Chemical and Materials Engineering, University of Alberta, Edmonton, Alberta, Canada
Show AbstractPolymeric materials producing nanomaterials in the form of nanoparticles, nanorods, nanowires, nanotubes, thin films, etc. is the key element for the success of the nanotechnology, which gives extraordinary physical and chemical properties as a result of its nanosize.1-3 There have been proposals for numeral applications in the field of biomedicine, and some of them (such as sensors of DNA, the controlled release of drugs, tumor therapy, etc.) are close to achieving a successful development.4 Drug delivery systems developed through the combination of biocompatible materials and biodegradable constitute an important area of focus in the engineering of medical devices. In view of this, we Synthesized set of cross-linked sphere biodegradable polycaprolactone (PCL) nanoparticles with and without out cross linker via oil/water solvent evaporation method. PCL was synthesized by ring opening polymerization technique using metal oxide as a catalyst and alcohol as an initiator, furthermore, they are modified with a photocrosslinking agent as the end groups. The nanoparticles (Nps) were synthesized by crosslinking the hydrophobic tail by UV light irradiation and hydrophilic drug was encapsulated by sonication method with the presence of stabilizer (polyvinyl alcohol). The crosslinked nanoparticle size was monodisperse with narrow size (~100 nm) whereas solitary PCL nanoparticles were poly disperse with higher diameter (>500nm). Transmission electron microscopy (TEM) analysis revealed that these nanoparticles are assembled with hydrophobic tail structures cross-linked tail on outer sphere. The drug encapsulation efficiency controlled release is mainly influenced by the molecular weight and outer sphere content of the nanoparticles structure. The drug encapsulated crosslinked nanoparticles exhibit a pH-dependent release behavior in vitro, within 60 hours the complete drug was released in all the three pH condition pH 4, 5 and 7.4. Importantly, this novel nanoparticles system for cytotoxicity studies were carried out with cancer cell lines and it was found that these NPs system were biocompatible. Encapsulation of drug with cross-linked NPs shows comprehensive results, justifying the potential use of drugs with greater absorption cellular, sustained release, and retard the cancer cells.
Overall, these results suggest that cross-linked outer sphere biodegradable nanoparticle system are likely to have a great potential as therapeutic agents.
References.
1. K. Avgoustakis, A. Beletsi, Z. Panagi, P. Klepetsanis, A. G. Karydas and D. S. Ithakissios, J. Control. Release, 202, 79, 123–135.
2. L. Brannon-Peppas, int. J. Pharm, 1995, 116, 1-9.
3. R. H. Kollarigowda, RSC Advances, 2015, 5, 102143-102146.
4. R. CP, N. RJ, R. AJ and V. F, Nanomedicine, 2006, 2, 8-21.
10:00 AM - SM8.5.03/NM10.03
Maintenance of Neural Progenitor Cell Stemness in 3D Hydrogels Requires Matrix Remodeling
Christopher Madl 1 , Ruby Dewi 1 , Cong Dinh 1 , Kyle Lampe 1 2 , Duong Nguyen 3 , Annika Enejder 3 , Sarah Heilshorn 1
1 , Stanford University, Stanford, California, United States, 2 , University of Virginia, Charlottesville, Virginia, United States, 3 , Chalmers University of Technology, Gothenburg Sweden
Show AbstractWhile neural progenitor cells (NPCs) hold significant therapeutic promise, the difficulty and cost of expanding a large number of stem cells remains a significant barrier to widespread clinical use. Recently, 3D hydrogels have been proposed as in vitro culture platforms for the expansion of stem cell populations to overcome the space limitations of 2D culture. However, very little is known about what 3D material properties are required to maintain NPCs in an undifferentiated state for expansion. It is well-established that matrix stiffness modulates stemness in strongly adherent stem cells, including mesenchymal stem cells and muscle satellite cells, but the impact of stiffness on stemness maintenance in non-adhesion-dependent stem cells such as NPCs is not well known. Furthermore, within 3D materials, matrix degradability is another crucial design parameter that can modulate stem cell behavior, as previous studies have shown that cells cannot spread, migrate, or proliferate without first degrading their surrounding matrix. To investigate the impact of matrix stiffness and degradability on NPC stemness, we designed a family of modular, engineered elastin-like protein (ELP) hydrogels with varying stiffness (E~0.5-50 kPa) and degradability. These ELP gels consisted of structural domains derived from elastin to provide tunable stiffness and bioactive domains to permit cell adhesion and matrix degradation. Strikingly, expression of the stem markers Nestin and Sox2 by embedded NPCs was not correlated with hydrogel stiffness over the range tested. However, expression of stem markers was strongly correlated with hydrogel degradability, with increased stem maintenance in more degradable hydrogels. NPCs cultured in high degradability hydrogels exhibited increased proliferation and enhanced differentiation potential, confirming that increased degradability was associated with maintenance of a functional stem phenotype. We identified that NPCs utilize the protease ADAM9 to regulate matrix remodeling in the ELP gels. Accordingly, knockdown of ADAM9 inhibited NPC-mediated hydrogel degradation and resulted in a loss of stemness. To confirm that ADAM9-mediated remodeling is a generalizable mechanism for maintaining NPC stemness in 3D, we designed a second hydrogel system based on peptide-crosslinked poly(ethylene glycol) with independent tuning of stiffness (E~0.5-2 kPa) and ADAM9 degradability. Consistent with our findings using the ELP gels, stemness was maintained in hydrogels susceptible to degradation by ADAM9 independent of stiffness, while non-ADAM9 degradable gels resulted in a loss of NPC stemness. Our results have identified matrix remodeling as a previously unknown requirement for maintenance of NPC stemness in 3D hydrogels and suggest that ADAM9-degradable materials may be useful for expansion of therapeutically relevant numbers of undifferentiated NPCs.
10:15 AM - SM8.5.04/NM10.04
Selective Packaging of pDNA into Rod- or Toroid-Shape within Polyplex Micelles
Kensuke Osada 1 , Yanmin Li 1 , Kazunori Kataoka 2 1
1 , University of Tokyo, Tokyo Japan, 2 , Innovation Center of NanoMedicine (iCONM) , Kawasaki Japan
Show AbstractDNA undergoes large conformational transition from hydrated coil to dehydrated compact form upon polyion complexation (PIC) with polycations. The volume transition, called DNA condensation, receives remarkable attention because this is essential of the nucleosome formation and is an important part in preparation of gene delivery system. In this study, using block catiomers composed of poly(ethylene glycol) (PEG) and polycations, condensation behavior of plasmid DNA (pDNA) was investigated to accommodate a fundamental interest; how the micrometer-length pDNA changes its conformation and packaged into 100 nm-sized PIC assembly, namely polyplex micelles (PMs), within the constraint of inherent rigidity of the double-stranded DNA. Moreover, the packaged pDNA structure was attempted for control into particular ordered structures, as they are acknowledged to be relevant for eliciting biofunction of pDNA. Here, we show a success of selective packaging of pDNA into either rod-like structure or toroidal structure by modulating interactive potency between pDNA and block catiomers to form PMs, and explored potential biological activities of each structure as a gene delivery system. Interestingly, the toroid-shaped structure held intriguing biological functions; not only capable of elevating in vitro transcription efficiency but also of elevating in vivo gene transduction efficiency compared to the rod-shaped structure, which have been addressed as potent delivery system. This result demonstrated a tempting utility of the toroid structure as a novel-structured gene delivery system.
10:30 AM - *SM8.5.05/NM10.05
Metal-Organic Frameworks for Biotechnology
Paolo Falcaro 1 , Raffaele Ricco 1
1 , TuGraz, Graz Austria
Show AbstractAmong the different classes of Metal-Organic Framework (MOF) composites prepared during recent years using ceramic, metallic and polymeric nanoparticles,1,2,3,4 a new emerging type of MOF composite has been recently obtained encapsulating bio-macromolecules within MOFs.5,6,7 Thanks to different water-based synthetic approaches such as co-precipitation and biomimetic mineralization methods, different types of MOFs have been self-assembled around bio-active compounds (e.g. enzymes). These new bio-composites have shown unprecedented properties for the protection and release of proteins. This strategy enables the fast encapsulation of guests larger than micropores of MOFs. Remarkably, this novel approach overcomes the need for MOFs with pores larger than the hosted biomolecules, and enable one-pot syntheses as an alternative preparation route to post infiltration methods.8 Thus, MOFs are now considered promising materials for biotechnological applications as the encapsulation technique is inexpensive, effective and fast.6
In this presentation, an overview ranging from the exploitation of simple proteins and their constituents (amino acids)9 to complex biological systems for the formation of MOFs will be provided. The functional properties of these composites will be disclosed providing examples of other methods used for the encapsulation of proteins within MOFs, including the preparation of hollow MOF capsules.11,12 Comparison of the protective properties will be illustrated10 and the applications of proteins for the controlled localization of MOFs discussed.13 The exciting challenges and promising applications of these new MOF composites in biotechnology will be presented.
References
(1) Falcaro, Ricco, Yazdi, Imaz, Furukawa, Maspoch, Ameloot, Evans, Doonan Coord. Chem. Rev. 2016.
(2) Zhu, Xu Chem Soc Rev 2014.
(3) Doherty, Buso, Hill, Furukawa, Kitagawa, Falcaro, Acc. Chem. Res. 2014.
(4) Li, Kobayashi, Taylor, Ikeda, Kubota, Kato, Takata, Yamamoto, Toh, Matsumura, Kitagawa Nat. Mater. 2014.
(5) Lyu, Zhang, Zare, Ge, Liu, Nano Lett. 2014.
(6) Liang, Ricco, Doherty, Styles, Bell, Kirby, Mudie, Haylock, Hill, Doonan, Falcaro Nat. Commun. 2015.
(7) Shieh, Wang, Yen, Wu, Dutta, Chou, Morabito, Hu, Hsu, Wu, Tsung J. Am. Chem. Soc. 2015.
(8) Lykourinou, Chen, Wang, Meng, Hoang, Ming, Musselman, Ma J. Am. Chem. Soc. 2011.
(9) Liang, Riccò, Doherty, Styles, Falcaro CrystEngComm 2016.
(10) Liang, Coghlan, Bell, Doonan, Falcaro Chem Commun 2016.
(11) Huo, Aguilera-Sigalat, El-Hankari, Bradshaw Chem. Sci. 2014.
(12) Jeong, Ricco, Liang, Ludwig, Kim, Falcaro, Kim Chem. Mater. 2015.
(13) Liang, Carbonell, Styles, Ricco, Cui, Richardson, Maspoch, Caruso, Falcaro Adv. Mater. 2015.
11:30 AM - SM8.5.06/NM10.06
Mimicking Matrix Vesicles to Enhance Biomineralization of Osteoblast Cells
Fabian Itel 1 , Brigitte Stadler 1
1 , Aarhus University, Aarhus Denmark
Show AbstractLoad-bearing implants such as artificial hip or knee joints require a stable interface with bone tissue. Bioactive glass or bioactive ceramics as bulk implants or as surface coatings have so far proven to be the most successful concepts used in clinics due to their ability to induce osteoconduction or even osteostimulation. However, these ceramic and glass implants are difficult to fabricate and suffer from selective mechanical properties. Here, we aim to improve the osteoconduction of bone-forming osteoblast cells by providing a triggered mineralization at the bone tissue-implant interface. Specifically, we develop a kick-start for osteoblasts to produce extracellular matrix (ECM) and mineralization and, thus, provide a faster integration of implants within bone tissue. Our approach involves the assembly of artificial bone cells, which are composed of ECM components and matrix vesicles (MVs). Both components are important for the initial mechanism of bone mineralization. MVs are 100 nm-sized phosphatidylserine- (PS) and alkaline phosphatase (AP)-containing liposomes secreted by osteoblasts. Calcium phosphate (CaP) crystals are formed within MVs and adhere to the ECM of bone tissue, where further mineralization takes place on collagen fibrils. Our artificial bone cells are assembled in two different ways to form “soft” and “hard” microparticles using droplet-microfluidics to form agarose (hydrogel) microbeads and the layer-by-layer technique to assemble core-shell particles, respectively. Our key requirements are that the artificial bone cells i) have similar sizes to biological osteoblasts, ii) are composed of collagen fibers and iii) contain artificial MVs composed of PS-containing liposomes with encapsulated AP enzymes. AP cleaves phosphate ions from phosphomonoester substrates, which can be added to the cell media and induces CaP crystallization. Furthermore, the particle surface is crucial for cell adherence and cell interaction. Therefore, different surface coatings are employed including polydopamine, poly-L-lysine, collagen, and growth factors. The “soft” and the “hard” artificial bone cells are then compared by coculturing them with bone-forming Saos-2 cells (sarcoma osteogenic cells). The rate of mineralization is assessed by quantifying the produced mineral content and the number of cells in presence or absence of the artificial bone cells. We anticipate that our approach has the potential to enhance osteoblast-mediated bone formation.
11:45 AM - SM8.5.07/NM10.07
Micro-Fabricated Thermoresponsive Polymer-Grafted Surface for Producing Contractile Muscle Tissue Construct
Hironobu Takahashi 1 , Tatsuya Shimizu 1 , Masayuki Yamato 1 , Teruo Okano 1
1 , Tokyo Women's Medical University, Tokyo Japan
Show AbstractComplex structural organization in the body is a key factor to produce the appropriate tissue functionality. In mature skeletal muscle, for example, the muscle fibers are highly oriented to produce its mechanical functions. To engineer biomimetic tissues, therefore, a technique for mimicking microstructures in native tissues is required. Thermoresponsive poly(N-isopropylacrylamide) (PIPAAm)-grafted surface allows harvesting a cell monolayer as a single continuous cell sheet from the culture surface. Since cell sheets can be layered to produce 3D tissue construct, this cell sheet-based technology have been used effectively in the field of tissue engineering. In this study, a micro-fabricated thermoresponsive cell culture substrate was prepared to produce cell sheets composed of aligned cells. To control cell orientation in a cell sheet, stripe-shaped micro-patterns was fabricated on the thermoresponsive surface. Using this surface, we have engineered 3D muscle tissue having aligned orientation.
First, hydrophilic polyacrylamide (PAAm) was grafted spatio-selectively on a thermoresponsive surface through a photo-induced polymerization process. As a result, stripe patterns of PAAm-co-PIPAAm and PIPAAm regions (50 μm / 50 μm) was fabricated. Muscle progenitor cells, myoblasts, were aligned on the surface and reached to confluence by seeding onto the surface at 37 °C. Next, to produce a 3D tissue construct, multiple cell sheets were harvested from the surface and then layered using a gelatin gel-coated manipulator. Using this technique, multiple cell sheets were successfully layered while maintaining the cell orientation as designed. Interestingly, in the tissue construct, it was observed that aligned myoblasts changed their orientation by themselves. For example, when two cell sheets composed of aligned myoblasts were layered perpendicularly, all myoblasts of the bottom sheet re-oriented in the same direction of the top cell sheet. Using this unique behavior of myoblast, an aligned myotube construct was able to be produce by layering one aligned cell sheet and two random cell sheets. The randomly-oriented myoblasts were finally well aligned within the multilayer cell sheet construct through the self-organization process. Furthermore, the tissue construct was transferred onto a collagen gel and incubated in differentiation medium for 3 weeks. The resultant myotubes contracted by electrical pulse stimulation. Importantly, the muscle contraction was regulated directionally because of the aligned orientation of the construct.
In conclusion, we have developed a novel technique to create a muscle tissue construct through a cell sheet layering process. Uniquely, myoblasts self-organized their orientation within the tissue construct and showed regulated contraction by electrical stimulation. This structural design and functionalization could lead to truly biomimetic tissue generation, and development of in-vitro physiological tissue models.
12:00 PM - *SM8.5.08/NM10.08
Mechanobiology, Pluripotent Stem Cells, and Early Embryonic Development
Jianping Fu 1
1 , University of Michigan, Ann Arbor, Ann Arbor, Michigan, United States
Show AbstractResearch on human pluripotent stem cells (hPSCs) has significant promise for regenerative medicine, disease modeling, and developmental biology studies. In this talk, I will discuss our effort in leveraging the mechanobiology of hPSCs in conjunction with some synthetic biomimetic systems to recapitulate and model human early embryonic development. I will first discuss our effort in constructing microengineered stem cell models of early human neurological developmental processes. Specifically, we have utilized microengineered hPSC cultures to develop autonomously regionalized neuroectoderm tissues in vitro. Importantly, our findings have suggested that induction and regionalization of neuroectoderm tissues involve mechanically gated molecular signaling (including Wnt, Hippo, and BMP) through regulations of cell shape and cytoskeleton contractility to reinforce spatial patterning of cell fates in neuroectoderm tissues. Together, our data provide strong evidence supporting critical involvements of cellular mechanics and mechanobiology as control mechanisms in ensuing robust formation of regionalized neuroectoderm tissues. In the last part of my talk, I will describe an efficient method to generate early human amniotic tissue in vitro through self-organized development of hPSCs in a bioengineered niche that mimics the in vivo implantation environment. Biophysical signals from the implantation-like niche act as a switch to toggle hPSC self-renewal versus amniogenesis. Our study unveils a self-organizing nature of human amniogenesis and establishes the first hPSC-based model system for investigating peri-implantation human amnion development.
12:30 PM - SM8.5.09/NM10.09
Stabilization of Enzymes Using a Protein Matrix Identified from Squid Sucker Ring Teeth
Chelsea Riegel 1 2 , Patrick Dennis 1 , Marquise Crosby 1 , Matthew Dickerson 1 , Rajesh Naik 3
1 Materials and Manufacturing Directorate, Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio, United States, 2 , UES Inc, Dayton, Ohio, United States, 3 711 Human Performance Wing, Air Force Research Laboratory, Wright-Patterson Air Force Base, Ohio, United States
Show AbstractProtein entrapment has demonstrated great promise in the area of enzyme and biomolecule stabilization. Silk fibroin derived from the Bombyx mori silkworm, has been shown to stabilize a number of biomolecules including enzymes, vaccines and antibiotics. This is due to the highly repetitive amino acid structure of silk fibroin which lends the ability to self-assemble into ordered microcrystalline domains. The ordered structure of silk fibroin is hypothesized to create a “molecular crowding” regime where biomolecules and enzymes are stabilized through the prevention of unfolding. Based on the success of silk fibroin as a stabilizing excipient, we have looked at other potential protein matrices for their ability to stabilize labile biomolecules. The protein, suckerin-12 (S12), derived from the sucker ring teeth of the Humboldt squid, offers unique properties and potential advantages over silk fibroin, including a greatly reduced monomeric molecular weight, a more defined repeat structure and the ability to express large amounts of the protein recombinantly. Recently, S12 based hydrogels have been investigated for their shape changing properties, where under certain buffer conditions, they are induced to condense into a dehydrated state, reversibly. The potential for tunable molecular crowding led us to investigate whether S12 based hydrogels have the ability to protect labile enzymes from environmental insults. Here we present the effects of enzyme adsorption into S12 hydrogels in terms of heat stability and the ability to withstand a number of chemical insults. In this study, the ability of S12 hydrogels to protect enzymes from damage is compared to that of silk fibroin.
12:45 PM - SM8.5.10/NM10.10
Systemic Administration of Enzyme-Responsive Nanocapsules for Promoting Bone Repair
Hongzhao Qi 1 , Xiaolei Sun 2 , Xue Li 3 , Zhaoyang Li 1 , Jin Zhao 1 , Xin Hou 1 , Xubo Yuan 1 , Yunde Liu 3 , Zhenduo Cui 1 , Yunfeng Lu 4 , Xianjin Yang 1
1 Tianjin Key Laboratory of Composite and Functional Materials, School of Materials Science and Engineering, Tianjin University, Tianjin China, 2 , Department of Orthopedics, Tianjin Hospital, Tianjin China, 3 Department of Clinical Microbiology, School of Laboratory Medicine, Tianjin Medical University, Tianjin China, 4 Department of Chemical and Biomolecular Engineering, University of California, Los Angeles, California, United States
Show AbstractAccelerating the healing of fractures and bone defects by local delivery of growth factors possessing osteoinductive activity has been extensively demonstrated. Unfortunately, fractures, such as osteoporotic vertebral compression fracture, are incapable of adopting such strategy because of the difficulty of surgery or in situ injection. Systemic administration of growth factors is considered to be the appropriate solution for these diseases. But the therapy was hampered by the poor in vivo stability of growth factors, inefficient distribution in fracture site and the potential side effects such as ectopic osteogenesis. To address this challenge, we here conceived a growth factor systemic delivery platform based on nanocapsules possessing bone fracture-targeting ability and enzyme-responsive releasing ability, taking the advantages of the unique physiological character of bone fracture, i.e., the rupture and leakage of blood vessels and the over-expression of matrix metalloproteinases (MMP). Bone morphogenetic protein-2 (BMP-2), 2-(methacryloyloxy)ethyl phosphorylcholine (MPC) and MMP-degradable peptide were chosen as the model growth factor, monomer and crosslinker, respectively. Electrostatic and hydrogen bonding interactions enriched the monomers and crosslinkers around BMP-2 molecules and in situ free radical polymerization formed a thin polymer layer around BMP-2s, forming the nanocapsules with controlled composition. These nanocapsules are of uniform small size (~30 nm) possessing long circulation time (half-life is ~40 h) and can be passively targeted to fracture site through the ruptured and leaked blood vessels after systemic administration. Once accumulated in fracture site, the shells of nanocapsules could be degraded by MMP and thus BMP-2s were released. Animal experiments prove BMP-2 nanocapsules show better bone repair ability than native BMP-2. Furthermore, owe to the improvement of biodistribution of BMP-2 and the enzyme-responsive releasing characteristic, systemic administration of BMP-2 nanocapsules didn’t cause obvious ectopic osteogenesis. The results of this study demonstrate nanocapsules can enhance the in vivo stability and fracture sites delivery efficiency of growth factors and avoid their ectopic osteogenesis potential, realizing the repair of bone fracture by systemic administration of growth factors.
SM8.6: Bioinspired Materials
Session Chairs
Wednesday PM, April 19, 2017
PCC North, 100 Level, Room 124 A
2:30 PM - SM8.6.01
Effect of Drug-Polymer Interaction on Mechanical and Release Behavior of Drug-Eluting Fibers
Shih-Feng Chou 1 2 , Kim Woodrow 2
1 Mechanical Engineering, University of Texas at Tyler, Tyler, Texas, United States, 2 Bioengineering, University of Washington, Seattle, Washington, United States
Show AbstractElectrospun drug-eluting fibers have demonstrated advantages in loading efficiency and ability to tune release profiles compared to other therapeutic carriers used for implantable medical devices. In such instance, the mechanical performance of fibers may be significantly affected by the high drug loading. However the effect of drug loading on the mechanical integrity and release behavior of the delivery system has not been fully investigated but is integral for function. Here, we measure bulk mechanical properties of blend fibers made from polycaprolactone (PCL) and poly(D,L-lactic-co-glycolic) acid (PLGA) at various weight ratios and combined with up to 40 wt% of a small molecule water-soluble drug (tenofovir, TFV) to inform drug-polymer interactions at the molecular level. Dogbone specimens were prepared by punching the electrospun fiber mats from a stainless steel die for tensile testing on an Instron. Young’s moduli were used for the development of a Voigt model to estimate drug partition in the blend fibers. HPLC analysis was used to quantify drug concentration in the release media for up to 10 days.
Uniaxial tensile tests performed on electrospun fibers made with various PCL/PLGA ratios and drug loadings revealed drug-polymer interactions. Average Young’s moduli and tensile strength of blank PCL/PLGA fibers gradually increased with increasing PLGA contents in the blend fibers. However, TFV loaded fibers suggested a different trend of mechanical properties from blank fibers, indicating the effect of drug-polymer interactions. In addition, increasing drug loading to 40 wt% decreased the mechanical properties of PCL/PLGA 20:80 fibers due to a strong plasticizing effect from the drug, and consequently led to a burst release at higher drug loading. Results on fiber mechanical properties suggested a strong drug-polymer interaction, which mediates drug release rates. Dogbone samples collected from the release media at predetermined time points showed significant decreases in average Young’s modulus and tensile strength as compared to the blank fibers. The additional loss in mechanical properties was associated with drug release behaviors. Our results showed the dependence of fiber mechanical properties on drug release rates and biodegradation as a result of drug loading. Interestingly, TFV release rates increased in pre-stretched fibers. Mechanical assessment on drug partition in PCL/PLGA fibers suggested a higher drug content in the PCL phase than in the PLGA phase. This study contributes significantly to the understanding of drug-polymer interactions in electrospun drug-eluting fibers and provides important property information for implantable therapeutic carriers in future clinical applications.
2:45 PM - SM8.6.02
pH-Responsive, Lysine-Based, Hyperbranched Polymers Mimicking Cell-Penetrating Peptides for Efficient Intracellular Delivery
Shiqi Wang 1 , Rongjun Chen 1
1 , Imperial College London, London United Kingdom
Show AbstractThe insufficient delivery of biomacromolecular therapeutic agents into the cytoplasm of mammalian cells remains a major barrier to their pharmaceutical applications. Cell-penetrating peptides (CPPs) are considered as potential carriers for intracellular delivery of macromolecular drugs. However, due to the positive charge of most CPPs, strong non-specific cell membrane bindings may lead to relatively high toxicity. Herein, we report a series of anionic, cell-penetrating peptide-mimicking, lysine-based hyperbranched polymers, which were membrane-lytic at late endosomal pH while inactive at physiological pH. The polymers with different branching degrees were prepared by a facile one-pot synthetic strategy. To our knowledge, it is the first report of anionic, hyperbranched, CPP-mimicking polymers. The pH-responsive conformational alterations and the multivalency effect of the hyperbranched structures were demonstrated to effectively facilitate the interactions between the polymers and cell membranes, thus leading to significantly enhanced membrane-lytic activity compared with linear ones. The unique structures and pH-responsive cell-penetrating abilities make these polymers promising candidates for intracellular delivery and endosome release of biomacromolecular payloads.
3:00 PM - SM8.6.03
Fluorescent Molecular Force Probe that Operates in Soft Materials
Shohei Saito 1 , Hiroshi Yabu 2
1 , Kyoto University, Kyoto Japan, 2 , Tohoku University, Sendai Japan
Show AbstractForce mapping at molecular scale is an important technology in rheology and mechanobiology. Flexible and aromatic photoresponsive (FLAP) system has been developed as fluorescent molecular force probe, which shows force-responsive conformational change with fluorescence color conversion in a real-time and reversible manner. The FLAP molecules are useful for visualizing the stress concentration in polymer films and understanding the force transduction in biological systems.
Here we report the preparation of the FLAP-doped luminescent elastomer film that shows the reversible response to the mechanical stress, in which the flexible FLAP fluorophore is stretched to exhibit a different emission color. The unique dynamic fluorophore with single-component RGB luminescent properties has been synthesized based on the molecular design of rigid-flexible hybridization. In general, the conformational flexibility is key to switching fluorescence properties, while some planar, rigid structures are favorable for producing strong luminescent properties. To combine the advantages of flexibility and rigidity, we have designed and synthesized a hybrid pi system that consists of a flexible cyclooctatetraene (COT) core and anthraceneimide wings [1-3]. This hybrid pi system exhibits a conformation-dependent emission from a single component fluorophore. That is to say, the pi system gives rise to a blue emission from the V-shaped structure doped in a elastomer film, while a green emission was observed from the planar geometry which should be produced in the stretched elastomers. This result demonstrates that the FLAP molecule actually works as fluorescent force probe even in the condensed materials [4].
[1] S. Saito* et al., J. Am. Chem. Soc. 2013, 135, 8842−8845 (Highlighted in C&EN).
[2] S. Saito* et al., Chem. Eur. J. 2014, 20, 2193–2200 (Inside Cover).
[3] S. Saito* et al., Nature Commun. 2016, 7, 12094.
[4] S. Saito* and H. Yabu* et al., to be submitted.
3:15 PM - SM8.6.04
Rapid Electro-Formation of Robust and Transparent Biopolymer Gels in Prescribed 3D Shapes
Ankit Gargava 1 , Srinivasa Raghavan 1
1 , University of Maryland College Park, College Park, Maryland, United States
Show AbstractGels of biopolymers such as alginate are routinely used to encapsulate biological cells and proteins for applications in drug delivery and tissue engineering. These gels are created by combining sodium alginate with a source of divalent ions like Ca2+. Recently, researchers have demonstrated the ability to deposit alginate gels using electric fields. For example, these gels can be deposited at the anode of an electrochemical cell where the local pH is considerably more acidic than in the bulk solution. However, these processes are limited to generating 2-D films of alginate, and the need for strong pH gradients hampers the inclusion of pH-sensitive species within the films. Here, we present an alternative approach for rapidly forming 3-D alginate gels upon application of an electric field. In this approach, a molded 3-D gel of gelatin with dissolved CaCl2 is placed in a beaker containing a sodium alginate solution. These are connected to a DC power source, and when a voltage is applied, an alginate/Ca2+ gel is formed around the gelatin in a shape that is the inverse replica of the original mold. The alginate gels are transparent and robust, and the process is mild and compatible with pH-sensitive materials. Gels in several 3-D architectures can be formed by this method that cannot be achieved through conventional methods.
4:30 PM - SM8.6.05
Self-Assembly of Repeat Polypeptides
Isaac Weitzhandler 1 , Ingo Hoffmann 2 , Sylvain Prevost 3 , Jonathan McDaniel 4 , Michael Dzuricky 1 , Michael Gradzielski 5 , Ashutosh Chilkoti 1
1 Biomedical Engineering, Duke University, Durham, North Carolina, United States, 2 , Institut Laue Langevin, Grenoble France, 3 , European Synchrotron Radiation Facility, Grenoble France, 4 Chemical Engineering, University of Texas at Austin, Austin, Texas, United States, 5 Physical Chemisry, Technische Universitat Berlin, Berlin Germany
Show AbstractIn recent decades, block copolymers have been studied extensively. When the blocks have different solubilities, block copolymers can self-assemble into a range of structures including micelles, vesicles, lamellae, and liquid crystals. In recent years, recombinant DNA techniques have allowed for the development of repeat polypeptides such as elastin-like, resilin-like, and silk-like polypeptides. One considerable advantage of recombinant block copolypeptides is that because they are synthesized by a host organism from a specific DNA template, they are perfectly sequence-defined and monodisperse.
For synthetic block copolymers, the relationship between hydrophilic weight fraction, polymer hydrophobicity, charge, and self-assembly has been characterized theoretically, computationally, and experimentally. In the case of recombinant block copolypeptides however, despite the number of different sequences and self-assembled structures reported, there exists only a limited understanding of the relationship between polypeptide sequence and self-assembled morphology. The present work aims to address this shortcoming of the literature through the synthesis and characterization of systematically designed families of recombinant repeat block copolypeptides, thus revealing the “rules” governing their self-assembly.
The first set of repeat block copolypeptides consists of a high molecular weight, hydrophilic elastin-like polypeptide fused to a short hydrophobic block consisting of aromatic amino acids and glycine spacers. Despite their high hydrophilic weight fraction (in excess of 90%), these block copolypeptides self-assemble into cylindrical micelles, rather than the expected star-like morphology.
The second set of repeat block copolypeptides are resilin-like/elastin-like block copolypeptides wherein the molecular weight of the hydrophobic resilin-like block and the hydrophilicity of the hydrophilic elastin-like block are varied systematically. The self-assembly of these block copolypeptides obeys a number of simple rules from polymer physics relating to the hydrophobic weight fraction, the hydrophilicity of the corona-forming block, the morphology of the self-assembled micelles, and the polypeptide chain conformations.
The bulk phase, liquid crystalline self-assembly of repeat polypeptides was also characterized. Repeat polypeptides form highly ordered liquid crystalline phases such as hexagonally oriented cylinders and lamellae. The feature sizes are responsive to molecular weight and temperature. Upon the phase transition of one block, block copolypeptides exhibit both order-order and order-disorder transitions. These highly ordered bulk phases can be deposited on surfaces to form highly regular, biologically patterned surfaces, which enable many biomedical applications.
4:45 PM - SM8.6.06
Artificially Engineered Protein Polymer Materials for Selective Biomolecular Separation
Minkyu Kim 1 2 3 , Bradley Olsen 3
1 Department of Materials Science and Engineering, The University of Arizona, Tucson, Arizona, United States, 2 Department of Biomedical Engineering, The University of Arizona, Tucson, Arizona, United States, 3 Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, United States
Show AbstractUnderstanding the function of biological systems can provide inspiration to develop new functional materials, such as mussel byssus mimicking adhesives, muscle-inspired energy dissipative materials, and thermo-responsive elastin-based drug delivery vehicles. One of the interesting studied biological functions is the selective filtration through pores on the nuclear membrane. Traditional separation membranes nonspecifically filter small particles by decreasing membrane mesh sizes, which also reduces filtering rates. Alternatively, the nuclear membrane pores specifically filter only a small group of selected molecules, independent of size, at a very high rate between the cell cytoplasm and the nucleus while rejecting the passage of undesired molecules into the nucleus. The pore is filled with the gel network, composed of nucleoporins, proteins containing Phe-Gly (FG) repeat sequences that contribute to specific binding to nuclear transport receptors (NTRs). The selectivity of target molecules is achieved via complexation with NTRs that facilitate transport of the targets into the nucleoporin gel network. This fast, specific selectivity of biological filters, unprecedented in synthetic polymer membrane filters, makes them of interest scientifically as materials with a potential for broad impact in advanced separation technologies.
Inspired by the selective filtration by the nuclear membrane, a biopolymer system that can separate target biomolecules using a facilitated diffusion-based mechanism has been developed. The system includes two components: engineered NTRs fused with a peptide tag that can "catch" target biomolecules and a recently developed nucleoporin-like protein (NLP) polymer hydrogel that can selectively "trap" target molecule-NTR complexes via a similar selective filtering mechanism as the biological membrane. The NLP hydrogel is shown to effectively capture target molecule-NTR complexes present at single nanomolar concentrations in the environment. An 11-fold enrichment of target molecules to unselected environmental biomolecules is observed in the NLP gel compared to control gels, which do not contain FG repeats in the protein polymer network. We found that the high selectivity requires both moderate interactions between the hydrogel and the target-NTR complex as well as high gel concentration to reduce the hydrogel pore size. As a proof of concept of "catch-and-trap", a partial green fluorescent protein sequence and staphylococcal enterotoxin B toxoid, related to toxic shock syndrome, are both separated from biomolecule mixtures using NLP hydrogels and engineered NTRs that contain binding tags for the corresponding target molecules. This represents a versatile system for fusing NTRs with diverse peptide tags and enabling the selective binding and separation of a wide variety of biomolecules, such as high value antibodies and biological toxins, for biomedical, food toxicology and defense applications.
5:00 PM - *SM8.6.07
Protein-Engineered, Self-Assembling Bio-Inks for Cell-Based 3D Printing
Sarah Heilshorn 1
1 , Stanford University, Stanford, California, United States
Show AbstractDespite the rise of 3D printing of thermoplastics both in industry and the general public, a key limitation preventing the widespread use of cell-based 3D printing is the lack of suitable bio-inks that are cell-compatible and have the required properties for printing. Current commonly used biomaterials have distinct limitations when used as a bio-ink including difficulty maintaining a homogeneous cell suspension, avoiding cell damage during extrusion, customizing the printed matrix properties to facilitate cell-matrix interactions, and printing within a bath to prevent cell dehydration while preserving high print resolution. We have designed a new family of tunable biomaterials specifically designed for cell-based 3D printing. These hydrogel-based bio-inks are produced from blends of engineered recombinant proteins and peptide-modified, naturally occurring biopolymers such as alginate and hyaluronic acid. These materials undergo two-stages of crosslinking: (i) weak, peptide-based, self-assembly to homogeneously encapsulate cells in a shear-thinning hydrogel within the ink cartridge and (ii) stimuli-responsive crosslinking post-printing to rapidly stabilize the construct. Benefits of this two-stage crosslinking strategy include the prevention of cell sedimentation within the ink cartridge, mechanical shielding of the cell membrane from damaging extrusion forces during printing, rapid post-print self-assembly within an aqueous bath that prevents cell dehydration, and fine-tuning of the printed scaffold mechanical properties for optimal cell-matrix interactions.
5:30 PM - SM8.6.08
Materials Construction through Peptide Design and Solution Assembly into 1D or 2D Physical Polymers
Darrin Pochan 1
1 , University of Delaware, Newark, Delaware, United States
Show AbstractSelf-assembly of molecules is an attractive materials construction strategy due to its simplicity in application. By considering peptidic molecules in the bottom-up materials self-assembly design process, one can take advantage of inherently biomolecular attributes; intramolecular folding events, secondary structure, and electrostatic interactions; in addition to more traditional self-assembling molecular attributes such as amphiphilicty, to define hierarchical material structure and consequent properties. These self-assembled materials range from hydrogels for biomaterials to nanostructures with defined morphology and chemistry display for inorganic materials templating. The local nano- and overall network structure, and resultant viscoelastic and cell-level biological properties, of hydrogels that are formed via beta-hairpin self-assembly will be presented. Importantly, the hydrogels do not form until individual peptide molecules intramolecularly fold into a beta-hairpin conformation in response to specific solution stimuli. Subsequently, specific, intermolecular assembly occurs into a branched nanofibrillar network. These peptide hydrogels are potentially excellent scaffolds for tissue repair and regeneration due to inherent cytocompatibility, porous morphology, and shear-thinning but instant recovery viscoelastic properties. Slight design variations of the peptide sequence allow for tunability of the self-assembly/hydrogelation kinetics as well as the tunability of the local peptide nanostructure and hierarchical network structure. In turn, by controlling hydrogel self-assembly kinetics, one dictates the ultimate stiffness of the resultant network and the kinetics through which gelation occurs. During assembly and gelation, desired components can be encapsulated within the hydrogel network such as drug compounds and/or living cells to make composite systems. The system can shear thin but immediately reheal to preshear stiffness on the cessation of the shear stress. By using the shear-thinning, rehealing behavior, one can perform multiple injections to produce layered hydrogels, channels of hydrogel in a hydrogel matrix and domains of one hydrogel within another matrix. These composite constructs are critical for the mimicking of in vivo, multi-cell environments in the cerebellum in order to study the fundamental biology and disease states of the brain. Additionally, a new system comprised of coiled coil motifs designed theoretically to assemble into two-dimensional nanostructures not observed in nature will be introduced. The molecules and nanostructures are not natural sequences and provide opportunity for arbitrary nanostructure creation with peptides.
SM8.7: Poster Session II: Advanced Polymers
Session Chairs
LaShanda Korley
Muhammad Yasar Razzaq
Wednesday PM, April 19, 2017
Sheraton, Third Level, Phoenix Ballroom
9:00 PM - SM8.7.01
Laser Writing Assembly of Block Copolymer on Chemically Modified Graphene
Hyeong Min Jin 1 2 , Joonwon Lim 1 2 , Kyung Eun Lee 1 2 , Sang Ouk Kim 1 2
1 , KAIST, Daegeon Korea (the Republic of), 2 , National Creative Research Initiative Center for Multi-Dimensional Directed Nanoscale Assembly, Daejeon Korea (the Republic of)
Show AbstractPolymer self-assembly commonly suffers from retarded equilibrium structure formation arising from the large diffusion barrier of long chain molecules. We introduce low energy laser photothermal treatment to effectively promote the polymer self-assembly and achieve highly aligned 10-nm-scale patterned structures on arbitrary substrates. Weak intensity Infrared or visible laser beam is directly radiated at block copolymer thin films in an ambient condition for area-selective ultrafast self-assembly within several seconds. In-plane scanning of the laser beam induces directional self-assembly of laterally ordered vertical lamellar or cylinder nanodomains from quasi static order/disorder boundary. Solution processing of chemically modified graphene film is employed as flexible and conformal light absorbing layer to facilitate the laser writing self-assembly on transparent, nonplanar, and mechanically flexible surface geometry.
9:00 PM - SM8.7.02
Amyloid Structures Produced from Recombinant Gas Vesicle Proteins
Joseph Tang 1 2 , Claretta Sullivan 1 , Joseph Slocik 1 2 , Patrick Dennis 1 , Wendy Goodson 1
1 , Air Force Research Laboratory, Wright-Patterson AFB, Ohio, United States, 2 , UES, Inc., Dayton, Ohio, United States
Show AbstractBacterial micro-compartments (BMCs) are structures that perform unique biological functions in microorganisms. A notable trait of BMCs is their selective permeability to certain chemical species. For example, the carboxysome is permeable to HCO3–, but not CO2 and O2. Bacterial gas vesicles (GVs) are intracellular structures that play a role in the regulation of cellular buoyancy in response to light intensity. Like the BMCs, these structures consist of a protein shell that is permeable to various gas molecules, but not water or ions. Genes encoding GV associated proteins from cyanobacteria and halobacteria have been identified, but the biochemical and biophysical properties of these proteins as well as their ability to self-assemble into functional structures are not yet fully understood. In an effort to employ GVs for biomaterials and bioengineering applications, we have developed a methodology for the production and purification of recombinant GV components. Under the proper conditions, these components self-assemble into amyloid-like structures that demonstrate buoyant behavior in aqueous solution. The characterization of these amyloid-like structures is presented here.
9:00 PM - SM8.7.03
Study of Protein-Carbohydrate Covalent Linkage in Gelling Arabinoxlyans
Mayra Mendez-Encinas 1 , Elizabeth Carvajal-Millan 1 , Ciria Figueroa-Soto 1 , Elisa Valenzuela-Soto 1 , Madhav Yadav 2 , Agustin Rascon Chu 1 , Yolanda Lopez-Franco 1 , Jaime Lizardi-Mendoza 1 , Alberto Nunez 2
1 , CIAD, Hermosillo, Sonora, Mexico, 2 , USDA, Wyndmoor, Pennsylvania, United States
Show AbstractArabinoxylans (AX) are polysaccharides from cereal grains. AX can form gels through covalent cross-linking of ferulic acid. The properties of AX gels depend on the structural characteristics such as protein content. The objective of the present study was to investigate the nature of protein-carbohydrate covalent linkage in gelling AX. The protein associated to AX was studied by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and showed a molecular weight range from 6 up to 14 kDa. The matrix-assisted laser desorption/ionization with automated tandem time-of-flight mass spectrometry of the protein produced an amino acid partial sequence: alanine, threonine, tryptophan, glutamic acid, glycine, glutamic acid and arginine. The most abundant amino acids in protein were histidine, aspartic acid and threonine. The protein fraction attached to AX was removed using the enzyme O-glycosidase, suggesting an O-glycosidic covalent linkage between AX and the protein through serine and/or threonine.
9:00 PM - SM8.7.04
Polymer–Industrial Waste Fly Ash Cenosphere (FAC) Composite Film for Electromagnetic Interference Shielding
Pritom Bora 1 , K Vinoy 1 , . Kishore 1 , Praveen Ramamurthy 1
1 , Indian Institute of Science, Bangalore India
Show AbstractFly ash cenosphere (FAC), an industrial waste product rich in alumina (Al2O3) and silica (SiO2) (typically hollow microsphere), with an average size ~ 50 µm was cleaned by acid-base treatment followed by vacuum drying. The NiO is coated over FAC through chemical heterogeneous precipitation and thermal reduction (at 700 oC) method. The coating thickness was observed to be ~ 800 nm under optimal conditions. The oxidative polymerization of aniline on NiO-FAC composites were carried out under nitrogen at -30±2 oC and PANI-NiO-FAC composite was synthesized. Thus, obtained PANI-NiO-FAC composites were solution processed using DMPU followed by acid vapour treatment and also used as filler in weather resistive polyvinylbutyral (PVB) to get free standing flexible films. The surface morphology of the prepared films were studied along with elemental mapping. The electromagnetic interference shielding effectiveness (EMI SE) of as prepared composite films were investigated in J-band (5.8-8.2 GHz), X-band (8.2-12.4 GHz) and Ku-band (12.4-18 GHz) by using a vector network analyzer (complete two port thru-reflect-line calibration was performed in all the frequency bands before measurements). The most effective average EMI SE ~ 23 dB (20 dB EMI SE corresponds to 99 % shielding) was observed for PANI-NiO-FAC composite film (81±2 µm) whereas PANI-FAC composite film (80±2 µm) shows ~ 17 dB EMI SE. The optimally prepared flexible PVB-PANI-NiO-FAC composite film (279±2 µm) shows ~ 22 dB average EMI SE, comparatively higher EMI SE than PVB-PANI-FAC composite film (285±2 µm, ~17 dB). The EMI shielding due to absorption (SEA) was found to be intrinsically dominant for each composite film. Further, enhancement of microwave conductivity, total dielectric loss, EM attenuation constant with frequency indicates excellent EMI SE (SEA) of these composite films. These films can be coated over any substrate and a potential candidate to protect against EMI for modern communication devices, unmanned vehicles, robotics as well as microwave engineering.
9:00 PM - SM8.7.05
Syneresis in Arabinoxylan Gels—Rheology and Microstructure
Ana Maria Morales-Burgos 1 , Elizabeth Carvajal-Millan 1 , Norberto Sotelo-Cruz 2 , Agustin Rascon Chu 1 , Yolanda Lopez-Franco 1 , Jaime Lizardi-Mendoza 1
1 , CIAD, Hermosillo Mexico, 2 , Universidad de Sonora, Hermosillo Mexico
Show AbstractArabinoxylans (AX) gels have been studied as delivery matrices and could have potential applications for colon-specific drug delivery due to their porous structure, stability under changes in pH and temperature as well as their specific degradation by colonic microbiota. AX gels have been described as gels that present no syneresis, however, in the current investigation a maize bran AX containing a high amount of ferulic acid (7 µg/mg AX) presented this phenomenon. The kinetics of gelation of AX solutions at 1% and 2% (w/v) was rheologically monitored by small amplitude oscillatory shear following the storage (G’) and loss (G”) modulus over time. Maximum G’ values were 655 Pa and 889 Pa for AX at 1% and 2% (w/v), respectively. Covalent cross-linking structures (dimers and trimers of ferulic acid) content in AX gels at 1 and 2 % (w/v) increased after syneresis. The syneresis ratio (% Rs) of gels describes the amount of solvent released from the gel network. In the present work increasing AX concentration decreases % Rs value from 80 to 70 as result of the corresponding G’ increase. Scanning electron microscopy images of AX gels showed that after syneresis the microstructure of the gel was more compact and still heterogeneous. Syneresis effect was assumed to be result of the polymer network contraction by a slow further crosslinking of the chains due to further oxidation of ferulic acid.
9:00 PM - SM8.7.06
Molecular Identity and Viscoelastic Properties of Gelling Arabinoxylans Isolated by a Semi-Pilot Scale Procedure
Jose Fierro-Islas 1 , Elizabeth Carvajal-Millan 1 , Rafael Canett-Romero 2 , Agustin Rascon Chu 1 , Marcel Martinez-Porchas 1 , Jorge Marquez-Escalante 1 , Alma Campa-Mada 1
1 , CIAD, Hermosillo Mexico, 2 , Universidad de Sonora, Hermosillo Mexico
Show AbstractArabinoxylans (AX) are polysaccharides of cereal grains. Maize is the main source for bioethanol production in some countries. The dry milling of maize produces several co-products and bran represents the major fraction, which usually ends up in the distillers dried grain with solubles (DDGS). The development of high added-value products from DDGS has increased and could be used as a source for the potential extraction of AX. This polysaccharide is constituted of a linear backbone of xylose to which arabinose substituents are attached. Some of the arabinose residues are ester linked to ferulic acid. The presence of ferulic acid gives AX the ability to form covalent gels. In recent years, the interest in AX and AX gels has increased since several studies have reported that this biomaterial present prebiotic, antioxidant, antitumoral and immunomodulatory activity. In addition, AX gels could have potential applications on microencapsulation of macromolecules. The objective of this research was to extract AX from DDGS at a semi-pilot scale and determine their molecular identity and viscoelastic properties. The yield of AX was 4.2 % (w/w dry basis). Extracted AX were analyzed by Fourier Transform Infra-Red Spectroscopy (FT-IR) and small amplitude oscillatory shear. The spectral FT-IR pattern in region of 1200-850 cm-1 was characteristic of AX. The maximum absorption band (1035 cm-1) was assigned to C-OH bending and the signals at 1070 and 898 cm-1 were related to the antisymmetric C-O-C stretching mode of the glycosidic link and β(1-4) linkages between the sugar units. Gels at 2% in AX (w/v) presented an elasticity (G’) value of 77 Pa.
9:00 PM - SM8.7.07
Photocrosslinking of Methacrylated Pectin—pH Stability and Gelling Capability
Yaeel Cornejo-Ramirez 1 , Elizabeth Carvajal-Millan 1 , Francisco Brown-Bojorquez 2 , Alison Dominguez-Chavez 1 , Agustin Rascon Chu 1
1 CTAOV, Centro de Investigacion en Alimentacion, Hermosillo, Sonora, Mexico, 2 Polimeros, Universidad de Sonora, Hermosillo, Sonora, Mexico
Show AbstractThe pharmaceutical industry uses controlled release matrices for drug delivery in the human body. An important factor in oral administration is the pH stability of such matrices. Pectins have long been used as excipient for its suitable properties; however, pH sensibility of pectin gels is a major drawback for controlled delivery matrices. In this regard, the aim of this research was to determine the effect of methacrylic anhydride addition to low methoxy citrus pectin, on its physicochemical properties and gelling ability by photocrosslinking. First, the citrus pectin was chemically modified; 1% (w/v) pectin in phosphate buffer (pH 7) was mixed with methacrylic anhydride at 1:1, 1:2 and 1:3 proportions. The derivatization at 1:2 (pectin solution: methacrylic anhydride) ratio showed peaks by FT-IR at 949 cm-1, 1737 cm-1 and 1616 cm-1 wave number, which suggest the presence of the vinylidene group, the C=O and C=C bond, respectively in the structure of pectin. The HPLC chromatogram showed that the neutral sugars profile was not affected. Photocrosslinking was done for a 3% (w/v) pectin solution with 10% (v/v) 2-Hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone solution as a photoinitiator at 265 nm during 5 min. The modified pectin gel presented a strength of 0.022±0.003N/ mm; 1.55 times lower than unmodified citrus pectin ionic hydrogels. Interestingly, the photocrosslinked hydrogel was stable at acidic and basic pH, but not at neutral pH. Photocrosslinked hydrogel have enough firmness to remain intact through the digestive tract conditions; in theory, the gels could be disintegrated by pH in the colon. Further research is required to fully assess the potential of photocrosslinked pectin hydrogels for design of controlled/ target delivery matrices.
9:00 PM - SM8.7.08
Sugary Interfaces Mitigate Contact Damage Where Stiff Meets Soft
Sangchul Rho 1 , Hee Young Yoo 1 , Sangsik Kim 1 , Dong Soo Hwang 1
1 , POSTECH, Pohang Korea (the Republic of)
Show AbstractThe byssal threads of the fan shell Atrina pectinata are non-living functional materials intimately associated with living tissue, which provide an intriguing paradigm of bionic interface for robust load-bearing device. An interfacial load-bearing protein (A. pectinata foot protein-1, apfp-1) with L-3,4-dihydroxyphenylalanine (DOPA)-containing and mannosebinding domains has been characterized from Atrina’s foot. apfp-1 was localized at the interface between stiff byssus and the soft tissue by immunochemical staining and confocal Raman imaging, implying that apfp-1 is an interfacial linker between the byssus and soft tissue, that is, the DOPA-containing domain interacts with itself and other byssal proteins via Fe3+–DOPA complexes, and the mannose-binding domain interacts with the soft tissue and cell membranes. Both DOPA- and sugar mediated bindings are reversible and robust under wet conditions. This work shows the combination of DOPA and sugar chemistry at asymmetric interfaces is unprecedented and highly relevant to bionic interface design for tissue engineering and bionic devices.
9:00 PM - SM8.7.10
Functionalization of Carbon Particles by Atom Transfer Radical Polymerization
Nurettin Sahiner 1 , Sultan B Sengel 1
1 , Canakkale Onsekiz Mart Univ, Canakkale Turkey
Show AbstractSpherical carbon particles (CPs) with controllable sizes and surfaces were prepared hydrothermal treatment using sucrose as precursor. The CP preparation was accomplished in two steps; firstly, dewatering of sucrose at low temperatures, and secondly carbonization at high temperatures. The micro/nano sized CPs were functionalized by N-isopropylacrylamide (NIPAM), 2-Acrylamido-2-methylpropane sulfonic acid (AMPS), (3-Acrylamidopropyl)-trimethylammonium chloride (APTMACI) to have the corresponding polymers on CPs. The monomers were grafted onto the CPs’ surface via atom transfer radical polymerization (ATRP). The grafting process was accomplished by oxidation of CPs to -OH groups, and then attaching macro initiator on the surfaces.
The size of polymers that were grown from the surface of CPs can be controlled by feed ratio of the used monomers. CPs with various functional group polymers on the surfaces were functionalized and characterized via FT-IR, NMR, SEM, TEM and TG analysis. Moreover, copolymerization of these monomer with different hydrophobic monomer to induce additional properties will be discussed. The responsive behaviors of CP-p(NIPAM), CP-p(AMPS) and CP-(APTMACl) composite in various solutions against environmental stimuli such as temperature, pH and ionic strength were investigated. These novel CPs-based micro/nanomaterials with tailoring structure, architecture, and properties are promising candidates for various biomedical, energy and environmental applications.
9:00 PM - SM8.7.11
Microgels Derived from Different Forms of Carrageenans, Kappa, Iota, and Lambda for Biomedical Applications
Nurettin Sahiner 1 , Selin Sagbas 1 , Selehattin Yilmaz 1
1 , Canakkale Onsekiz Mart University, Canakkale Turkey
Show AbstractPoly(Carrageenan) microgels were synthesized by three main types of carrageenan such as kappa (κ), iota (ι), and lambda (λ) by using divinyl sulfone or epoxy group containing crosslinkers via microemulsion technique. These natural based κ-, ι-, and λ-carrageenan microgels were chemically modified by various cationic and anionic agents such as 3-chloro2-hydroxy propyl ammonium chloride (3-CHPACl), diethylenetriamine (DETA), and Taurine (TA). Optical microscope, scanning electron microscope (SEM), dynamic light scattering (DLS), zeta potential measurements and FT-IR spectroscopy were used for the characterization of the particles. Antimicrobial properties of the poly(Carrageenan) microgels were determined against common bacteria such as against gram negative Escherichia coli ATCC 8739 and Pseudomonas aeruginosa ATCC 10145, and gram positive Staphylococcus aureus ATCC 6538 and Bacillus subtilis ATCC 6633 bacteria strains. Blood compatibility of the microgels was determined by protein adsorption, hemolysis and blood clotting tests. Furthermore, the microgels and their modified forms were also investigated for potential drug delivery vehicles in physiological conditions at pH 7.4, 37.5 oC.
9:00 PM - SM8.7.12
Copper-Chitosan Transparent Antimicrobial Coatings
Debirupa Mitra 1 , En-Tang Kang 1 , Ramanathan Kollengode 1 , Matthew Cove 1 , Koon Gee Neoh 1
1 , NUS, Singapore Singapore
Show AbstractHealth-care associated infections (HCAIs) cause considerable mortality and morbidity, and inanimate environmental surfaces in hospitals can act as pathogen reservoirs wherein pathogens are inadvertently transferred to patients via hands or gloves of healthcare workers. In our project, we seek to develop antimicrobial surface coatings which can reduce bacterial burden on hospital inanimate objects such as equipment panels and touchscreens. Our focus is on chitosan derivatives since chitosan is an inexpensive, nontoxic and a naturally derived polysaccharide which is known to possess broad antimicrobial activity. The quaternization of chitosan greatly increases its solubility in water as well as its antimicrobial efficacy. Quaternized chitosan (QCS) prepared with acrylate groups can be readily grafted on polymer films under UV irradiation to give highly stable, non-cytotoxic QCS coatings. These coatings can kill about 90% of bacterial cells, when placed in contact with contaminated droplets for 2 h. To further increase the bacterial killing efficacy, copper was introduced onto the QCS-grafted films via palladium-free electroless deposition process. The positively charged quaternary ammonium groups of QCS promote deposition of copper on the surface without any catalytic pre-treatment. The copper content of these modified films was determined to be ~ 4 µg/cm2 and both Cu(0) and Cu(II) states of copper were present on the surface. These coatings can reduce bacterial count by 95% and 100%, when placed in contact with contaminated droplets for 1 h and 1.5 h respectively. Additionally, the copper-containing films were found to have no significant cytotoxic effects on fibroblast cells placed in contact with these films. Thus, these transparent copper-containing films with high antibacterial efficacy can potentially be used over high-touch areas in hospitals to prevent pathogen transmission.
9:00 PM - SM8.7.13
Poly(lactic acid)/Cellulose Nanofibril/Epoxidized Soybean Oil Ternary System towards Tougher and Stiffer Nanocomposites
Xiangtao Meng 1 , Halil Tekinalp 1 , Soydan Ozcan 1
1 Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee, United States
Show AbstractPoly(lactic acid) (PLA) as a promising renewable and biodegradable thermoplastic polymer has received tremendous attentions in applications such as medical devices, packaging, and additive manufacturing. The broader application potentials, however, have been restricted largely by the inherent brittleness of PLA. While most of previous approaches, such as the use of plasticizers, were able to increase the ductility, the stiffness and strength of the composites were usually sacrificed. In the current study, cellulose nanofibril (CNF) as nanofiller and epoxidized soybean oil (ESO) as coupling agent were utilized in the PLA-CNF-ESO ternary composite system. Mechanical performances of the composites including stiffness, ductility, and toughness were significantly improved, comparing with those of pristine PLA, CNF-PLA, and ESO-PLA systems. For example, the ternary composites are 10-fold tougher than pristine PLA or PLA composites enhanced only with CNF. In the meantime, Young’s moduli and tensile strengths of the ternary composites are 20-44 % and 8-58 % higher than those of PLA-ESO binary composites. Interfacial interactions in CNF-ESO, CNF-PLA, and ESO-PLA interfaces were investigated by thermal analysis, spectroscopic and microscopic approaches. Possible mechanisms on how the ternary system enhances mechanical performances will also be discussed.
9:00 PM - SM8.7.14
Ratiometric Fluorescent Microspheres for Sensing Oxygen
Gang Li 1 , LanFeng Liang 2 , Chengzhu Liao 1 , Jiapei Jiang 1 , Yanqing Tian 1
1 Department of Materials Science and Engineering, Southern University of Science and Technology, Shenzhen, Guangdong, China, 2 , Southern University of Science and Technology, Shenzhen, Guangdong, China
Show AbstractPolymer microspheres have received much attention because of their superior thermal and solvent resistance, mechanical strength, surface activity and adsorption properties. In our research, monodisperse polystyrene microspheres with controlled diameters ranging from 600 nm to 2 mm have been prepared through dispersion polymerization. In order to maintain a narrow particle size distribution and achieve the controllable particle diameters, we adopted two-stage polymerization proposed by Mitchell A. Winnik[1]. We extended our research for mono-dispersed polystyrene-based oxygen sensors and expected the porous and well aligned structures of the microspheres can achieve high sensitivity and stability by adjusting oxygen permeability. For sensing oxygen accurately in complicated biological environment, our microsphere-based sensors were designed as ratiometric fluorescent sensors[2] in which an platinum octaethylporphyrin (PtOEP) fluorophore as an oxygen probe and rhodamibe B (Rhod) derivative fluorophore as an oxygen-insensitive internal reference were enwrapped. We called the modified microspheres “PR-PSMs” for short. Through the two-stage polymerization, core-shell structures were prepared with the properties of mono-dispersity and smooth surface. Under an excitation at 540 nm, two emission peaks at 580 nm and 650 nm were observed, in