Toward the Design of Novel Biodegradable Materials by Engineering the Protein-Colloid Interface

This dissertation focuses on development of protein-derived materials, with the goal of incorporation into biodegradable devices such as enzymatic fuel cells or light emitting diodes (LEDs). Proteins are the key building blocks, for their inherent functions, hierarchical 3D structures, diversity of functional groups, and natural biodegradability. The interfaces between proteins and colloidal materials were exploited in the rational design of these materials. First, enzyme-poly(acrylic acid) (PAA) conjugates with enhanced stability and catalytic efficiency were explored. Conjugation of cytochrome c (cyt c) to PAA dramatically improved cyt c peroxidase activity, achieving 34-fold enhancement in kcat. Here, polyanionic PAA controlled the pH microenvironment and suppressed wasteful reaction intermediates. Next, we conjugated brush-like poly(norbornene)-graft-poly(acrylic acid) (PNPAA) to cyt c, and found that conjugates retained their structure under denaturing conditions. We also produced a white emitting hydrogel from crosslinked bovine serum albumin (BSA) with fluorescent dyes incorporated. We explored the applications of this hydrogel in LED coating and pH biosensing. Additionally, we demonstrated enzymatic glucose detection by incorporation of the enzymes glucose oxidase and peroxidase into the gel. Finally, we demonstrated that cationic silica nanoparticles can regulate the aggregation behavior of poly-L-(glutamate) (PLG). In the early stages, increased PLG concentration at the NP surface increased the nucleation rate. As fiber growth proceeded, NP binding to the growing fiber slowed the growth rate. These effects were controlled by manipulating the PLG-nanoparticle binding affinity, such as by increasing the temperature. Together, these examples provide useful insights into the design of robust, protein-derived materials