UC Berkeley

The focus of this dissertation is on the development of a modular approach toward protein-based nanomaterials. Over the past billion years, nature has optimized proteins to sustain the complexities of life. The efficiency, reproducibility, and diversity of functions that proteins poses is unmatched by any biomimetic product. Successful integration of active proteins with synthetic polymers has the potential to combine the advantages of both the biological as well as the synthetic world. Proteins would provide materials with chemical heterogeneity, structural precision, catalytic activity, and system dynamics not offered by manmade materials, and polymers would provide a platform that is chemically diverse, processable, and robust. Protein-functionalized materials can clearly open a viable approach to improving current technologies and will positively impact the current paradigm of materials science and device engineering.

However, most proteins reside in aqueous media and the majority of their uses are for biomedical applications. Their insolubility and inability to remain functional in non-aqueous solvents as well as their susceptibility to high temperatures are major barriers preventing their general usage toward biofunctional hybrid materials. In order to make proteins viable building blocks in the materials community, proteins must be processable, their structure must remain stable during processing, and their function must be preserved post-fabrication. Reverse micelles have been shown to successfully encapsulate a variety of proteins and make them processable. Using common small molecules surfactants, protein-based materials can indeed be created without modification of the protein itself, but surfactants were observed to only meet the criteria for processability and lent itself to protein denaturation during and after processing.

Many non-covalent interactions of similar energy scales underlie protein folding, polymer chain conformation, protein-polymer interactions, polymer-solvent interactions, and solvent-protein interactions. The delicate balance of the various energetic contributions must be understood in order to manipulate these interactions without interfering with a protein’s structure and built-in functionality. Using a rational approach, statistically random heteropolymers were developed that provided increase stability of proteins in organic solvent and elevated temperatures without interfering with both protein folding as well as material fabrication. This rational approach limited the parameter workspace and provided boundaries in which polymers were synthesized. A mixture of structural characterization of protein-polymer complexes and spectroscopic analysis of protein-polymer interactions were used to identify polymers that optimized preservation of protein activity.

This development of statistically random heteropolymers provides a path toward protein-based materials. By mixing proteins, statistically random heteropolymers, and commercially available polymers, protein patterning and devices for catalysis were generated. This work demonstrates the potential of statistically random heteropolymers as a vehicle toward functional materials, opening up a wide range of possible applications, from sensors to catalysis to energy.