Controlling Naturally-Derived Polymer Enzymatic Degradation: A Plasma-Enhanced Chemical Vapor Deposition Approach

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Project Summary Biomaterial implants are natural or synthetic materials that can be placed in the body to improve human health in multiple ways, including delivering drugs to targeted regions of the body, healing wounds, and maintaining organ function. It is important that implants do not break down until they have performed their function. For example, stitches after tooth extractions can dissolve in a few weeks, but a hip replacement implant should be able to stay intact for years. When these implants degrade too quickly or not quickly enough, complications such as pain and infection can occur. The goal of our research is to address the need to develop implants for different applications by making biomaterials with a range of degradation times. The materials proposed in this research are made of silk, a naturally-derived material that interacts with the body without negative side effects. When silk is placed in the body, it is degraded by enzymes. The goal of our research is to create a range of silk materials with different degradation rates. Our approach is to control how enzymes access the silk surface by changing the atoms and molecules in the silk film surface. The method that will be used to change the chemistry of the silk surface is plasma-enhanced chemical vapor deposition (PECVD), which is a technique used to apply a thin coating to the silk with specific types of atoms. Silk film surface chemistry, wettability, and morphology will be assessed before and after PECVD to characterize any changes in the material. Following PECVD, silk films and untreated control films will be weighed and exposed to enzyme-containing solutions. Films will be removed from solution, dried, and weighed again to measure how much of the material has degraded. The specific objective of the proposed work is to use PECVD to customize the silk surface chemistry, thus controlling how the enzymes interact with the silk materials. The central hypothesis for this proposal is twofold 1) introducing a hydrophobic coating to silk films will decrease the rate of enzymatic degradation, and 2) introducing a hydrophilic coating to silk films will increase the rate of enzymatic degradation. This hypothesis is based on the ability for enzymes to adsorb to the silk film surface, which ultimately controls the enzymatic degradation of the film. This proposal is expected to result in a PECVD method to customize the degradation rate of silk through controlling the film chemistry. Our strategy is expected to inform a range of implant applications. This work will help to address our long-term research goal: to understand how tuning naturally-derived material (e.g., collagen, chitin, cellulose) surface chemistry controls susceptibility to enzymatic degradation. The proposed research will position me to be competitive for future awards (e.g., SC1, R15, R01) so that I can pursue this long-term goal. As I am in the beginning stage of my career, this proposal will provide me with the resources to establish myself as an independent researcher so that I can provide high-quality research experience to undergraduate and graduate students for many years to come.