Collections > Electronic Theses and Dissertations > Designing Biomimetically Inspired Materials for Potential Orthopedic Tissue Engineering Applications

Described herein is the progress made towards modifying and improving established Hydroxyapatite-Gelatin (HAp-Gel) bioceramics. Initial attempts to improve this composite were aimed at incorporating a biomimetic polymer into the HAp-Gel matrix in order to improve long-range interactions in the system. This was done in order to address shortcomings of HAp-Gelatin composites (e.g. low toughness) without sacrificing its favorable properties. Novel degradable copolymers were used, inspired by lactide and trimethylene carbonate monomers. These copolymers demonstrated tunable properties (e.g. molecular weight, glass transition temperature) and were shown to improve fiber bridging in a composite, without sacrificing biocompatibility. Unfortunately, these composites were plagued by poor interfacial adhesion. To address this, a catecholamine based polymer, polydopamine (PD), was incorporated into this HAp-Gel ceramic matrix. This macromolecule has demonstrated excellent adhesion to numerous substrates. This PD containing composite was shown to have a strong dependence of mechanical properties on processing temperature. Specifically, it was shown that at low temperatures, PD is able to polymerize unimpeded, while the sol-gel component is hindered. The sequential PD/sol-gel polymerizations leads to a unique interpenetrated polymer network with excellent mechanical properties and good biocompatibility. Finally, studies about catecholamine adhesives were expanded in order to study the structure-property relationship which leads to their remarkable polymerizations and adhesive properties. It was found that unbound catecholamines (e.g. catechol with propylamine) behave similarly to bound catecholamines such as dopamine. This result has profound implications on the design and implementation of catecholamine based adhesives, and further tests are underway to determine their ability to replace dopamine in bioceramic composites.