University of Connecticut |
Polymer Program SeminarFrom Silicone Oxide Nanodots to Artificial Vocal Folds: Advanced Materials by Design M.I.T. Friday, February 11, 2005 11:00 am , IMS Room 20 Exciting opportunities exist for the development of advanced materials with nanometer scale organizations and/or desired biological functions. This talk provides an overview of my research efforts in the fabrication of nanostructured surfaces and the synthesis and evaluation of biocompatible hydrogels for vocal fold regeneration. The ability to generate surface structures at the nanometer scale in a controlled fashion is a step forward towards bottom-up nanotechnology. Controlled growth of silicon oxide (SiO2) on organosilane-modified silicon wafer templates is discussed first. Different nanoscale structures with varying roughness were fabricated by controlling the reaction kinetics. Water contact angle analysis and protein adsorption study indicate that both surface chemical functionalities and nanometer scale topography have profound effects on surface wettability and protein organization. Another type of template that has been studied is block copolymer thin film. SiO2 can be grown selectively within the ordered nanopores generated from block copolymer of polystyrene and poly(methyl methacrylate). Reactive ion etching selectively removed the organic matrix, leaving free-standing SiO2 posts on silicon wafers. Alternatively, a surface patterned on the nanometer scale, comprised of an array of hexagonally packed SiO2 dots in an organic matrix defined by block copolymer of polystyrene and poly(ethylene oxide) was generated. Such ordered SiO2 nanostructures could have widespread uses for on-chip separations as well as sensory and optoelectronic applications. The second part of the talk focuses on the current effort towards vocal fold restoration using injectable hydrogels. During normal phonation, human vocal folds sustain more than 100 collisions per second. When the pliability of this complex biomechanical system is reduced by scarring, voice quality may be compromised. Injectable hydrogels that not only mimic the biomechanical characteristics of the vocal fold tissue but also exhibit prolonged in vivo residence time are attractive candidates for vocal fold regeneration. A series of injectable hydrogels based on hyaluronic acid (HA) were synthesized and characterized. Chemical modifications of HA afforded macromolecules that can be crosslinked to form hydrogels in situ. Synthetic polymers were incorporated into the hydrogel networks by covalent grafting or copolymerization in order to fine-tune the elasticity and stability of the resulting hydrogels. Conjugation of bulky functional groups to HA backbone led to HA derivatives that are resistant to enzymatic degradation. HA-based hydrogel microspheres with protective shells have also been synthesized and characterized. Novel mechanical experiments were carried out in order to measure the viscoelastic properties of the synthetic materials and vocal fold tissue at frequency range that is relevant to human phonation. In vivo evaluation of the hydrogel biomaterials is currently in progress.
. |