Selected Publications

1. Z=40 Z=0 Z=40 µm Z=0 µm Z=40 µm Z=0 µm Spinal Nerve Repair Techniques Jon Nickels – BMECollaborator: Dr. W. Frey Dr. Zin Khaing – Post Doc Scott Zawko – CHE Using novel techniques to incorporate regeneration enhancing cells into natural scaffolds of acellular nerve grafts, we are implementing the latest molecular tissue engineering strategies for in vivo nerve repair. Hyaluronic Acid Biomaterials for Drug Release Applications Synthesis of Novel Conducting Degradable Biomaterials Nathalie Guimard – Chemistry Co-advisor: Dr. J. Sessler Stephanie Seidlits – BME Co-advisor: Dr. J. Shear Hyaluronic acid is a polysaccharide that can be chemically crosslinked to produce swellable hydrogels that have high water content, resist non-specific protein adsorption and cell adhesion, and can be used as delivery vehicles. In seeking to develop a biocompatible, biodegradable polymer that is also electrically conductive, we have synthesized a quaterthiophene based polymer and are currently characterizing its molecular weight, surface properties, conductivity, and cell compatibility. IPNs of Collagen and Hyaluronic Acid for Neural Tissue Engineering HA Jae Young Lee – CHE C) A) ‘Direct-Write’ of 3D Submicron Structures in Hyaluronic Acid (HA) Hydrogels Collagen Live dead stain of PC12 cells on solvent cast polymer films, 48 h after cell seeding. B) D) Crosslinks Shalu Suri – BME Su Long – BME Co-advisor: Dr. X. Zhang Photocrosslinkable Interpenetrating Polymeric Networks (IPNs) of collagen and hyaluronic acid are being developed for use as implants in peripheral nerve injury. These IPNs have advantages over the individual component gels as they retain the chemical properties of both polymers, while possessing improved mechanical properties. Combination A Physical + Chemical stimuli Three-Dimensional Conductive Scaffolds John Fonner – BME Collaborator: Dr. P. Ren 10μm Cells interact with HA through multiple receptors but they typically do not adhere to HA alone. Thus, we are expanding the potential of HA-based hydrogels by modifying them with internal, 3D-patterned, submicron protein structures through a photochemical ‘direct-write’ process based on multiphoton excitation (MPE). Molecular Imprinted Polymers (MIPs) Hyaluronic Acid (HA) Hydrogels for Angiogenesis and Wound Healing Shahana Khurshid – BME Co-advisor: Dr. N. Peppas Leandro Forciniti – CHE Co-advisor: Dr. M. Zaman B Competition Vs. Physical stimulus: grooves Chemical stimulus: NGF Effects of Electric Field (EF) on Neuronal Development We are developing three dimensional electroconductive scaffolds to integrate the effects of axonal size structure and electrical stimuli with a view to enhancing axonal development and growth. 5 μm Immobilized NGF The goal of our research is to develop a recognitive biomaterial based on hyaluronic acid for use in the CNS. Current work focuses on developing MIPs for serotonin and L-Dopa. MIPs have cavities complementary in structure and polarity to the template. Erin Moffitt – BME Microchannels Neuron Taking advantage of the unique biochemical properties of hyaluronic acid (HA) we are developing a tunable biomaterial platform to study the effects of mechanical properties, ECM protein incorporation, and vascular cell type on angiogenesis. Hieu Nyugen – BME Endogenous electric fields (EF) are developmental cues that direct cell growth in vivo. We mimic EF by applying a current across the cell substrate and study its effect on cell development. Control of EF will allow us to direct neuron growth for nerve repair. Decellularized Nerve Grafts for Nerve Tissue Regeneration Cell Behavior Using Microfluidics Modeling of Cell Mechanisms Nikhil Dube – CHE My project involves the design of decellularized nerve grafts for nerve tissue repair. After characterization of their chemical, structural and biological properties, we plan to functionalize the grafts with neurotrophic growth factors and regeneration promoting cells and assess their efficacy for nerve tissue engineering. We present novel methodology to encapsulate and culture neurons in Ca-alginate micro-gel particles within a microfluidic device. By adjusting flow rate, pressure, and solution components, the encapsulated cells can be cultured in a simulated in vivo environment. We are using a two fold strategy – integrating both modeling and experimental techniques – to investigate and characterize neuronal axon formation on biomaterials containing different stimuli. Molecular Tissue Engineering Christine E. Schmidt, Ph.D.Laurence E. McMakin, Jr. Professor of Biomedical Engineering and Chemical Engineering Tel. 512-471-1690 schmidt@che.utexas.edu Combining insight into fundamental cell mechanisms, natural materials, and bioactive synthetic materials, our goal is to develop therapeutic devices to aid in nerve regeneration and communication with the nervous system. http://www.bme.utexas.edu/faculty/schmidt/ Electroactive Biomaterials Natural Materials Natural materials, such as hyaluronan and decellularized nerve grafts, offer advantages for the repair of damaged tissue as they inherently have many physical, chemical, and biological properties suited to wound healing environments. Hyaluronan can be chemically crosslinked to produce tissue engineered scaffolds that facilitate cell migration, wound healing and angiogenesis. Another focus is on the development of new techniques for nerve repair using engineered nerve fragments as graft materials for regeneration after spinal cord injury. Synthetic polymers are a versatile tissue engineering platform that can deliver localized physical, chemical, and electrical cues that are tailored to specific applications. In particular, electrical stimuli have been shown to promote wound healing. By customizing and characterizing degradation rates, surface properties, and structural conformations, electrically conductive polymers such as polypyrrole and polythiophene can provide a readily available, “off the shelf” scaffold for nerve regeneration and guided tissue growth. Polypyrrole (PPy) Functionalization SEM images of PPy film surface and cross section We use a novel binding peptide as a surface modification strategy for the conducting polymer, polypyrrole. I am experimentally determining the binding strength and mechanism for this interaction.  This is an important step toward applying this technology to problems of tissue engineering and biomaterial design. Modeling Polymer Surface Interactions By leveraging modern computational simulation methods, we can characterize the interaction between polypyrrole and binding peptides to better refine surface functionalization. Cell Mechanisms The cell mechanism group is optimizing conditions for neuronal cell regeneration. In particular, we are independently and simultaneously presenting physical and chemical cues to nerve cells using multidisciplinary techniques such as cell physiological modeling and microfluidic devices. Selected Publications Zawko, S.A., Q. Truong, C.E. Schmidt (in press). Drug Binding Hydrogels of Hyaluronic Acid Functionalized with Alpha-Cyclodextrin.Journal of Biomedical Materials Research. Deister, C., S. Aljabari, C.E. Schmidt (2007). Effects of collagen 1, fibronectin, laminin 1, and hyaluronic acid concentration on neurite extension.Journal of Biomaterials Science, Polymer Edition. 18(8):983-97. Guimard, N., N. Gomez, C.E. Schmidt (2007). Conducting Polymers in Biomedical Applications. Progress in Polymer Science. 32: 876, 92. (invited review) Gomez, N., J.Y. Lee, J.D. Nickels, C.E. Schmidt (2007). Micropatterned Polypyrrole: Combination of Electrical Stimulation and Contact Guidance of Neurons. Advanced Functional Materials. Gomez, N., S. Chen, C.E. Schmidt (2007). Polarization of Hippocampal Neurons with Competitive Surface Stimuli: Contact Guidance Cues are Preferred over Chemical Ligands.J. Royal Society Interface. 4(13): 223-233. Gomez, N., C.E. Schmidt (2007). Nerve Growth Factor-Immobilized Polypyrrole: Bioactive Electrically Conducting Polymer for Enhanced Neurite Extension. Journal of Biomedical Materials Research. 81A: 135-149. Gomez, N., Y. Lu, S. Chen, C.E. Schmidt (2007). Immobilized Nerve Growth Factor and Microtopography Have Distinct Effects on Polarization Versus Axon Elongation in Hippocampal Cells in Culture. Biomaterials. 28: 271-284.