Enhancing Electron Transfer at the Protein/Electrode Interface: Applications in Bioderived Solar Energy Conversion and Electrochemical Biosensors

Abstract

The process of photosynthesis has served as a natural solar energy conversion system in autotrophs for billions of years. This complex biological process provides inspiration and key machinery that may be utilized in developing novel, low cost solar-to-electricity platforms. Photosystem I (PSI) is a large photoactive protein that is easily extracted from green plants and interfaced with different materials to generate simple photoactive electrodes. In this dissertation, several advances were made to improve the photovoltaic performance of PSI-based devices. First, a novel conducting polymer-PSI composite was prepared through facile in situ electrochemical polymerization of aniline and PSI. These photoactive films were initially studied on gold electrodes, before later being grown on semiconducting substrates to act as the photosensitizing layer of solid-state biophotovoltaic devices. In other studies, controlling the orientation of PSI as assembled on metallic electrodes was explored. Here, a simple functionalization strategy was devised to selectively modify the protein during extraction and introduce a ligand for activated surface coupling. Self assembly of these modified PSI complexes yielded significant increases in photocurrent, derived from improved protein orientation. Additionally, a new type of low cost bioderived photovoltaic device was introduced featuring a solid-state polyviologen film that served as an electron transport layer between the PSI layer and anode. In a push to further drive down the cost of PSI-based devices, a streamlined PSI extraction procedure was developed that required minimal laboratory equipment and could be performed by a user with limited chemistry experience. Finally, enzymatic biosensors were prepared by coupling various oxidases with osmium hydrogel redox polymers. These redox active films were used to construct a multianalyte electrochemical biosensor platform capable of measuring changes in glucose, lactate, and glutamate over a high background of an electroactive interferent (i.e. acetaminophen). These biosensors represent a new system that can be interfaced online with an Organ-on-Chip system to make electrochemical measurements in real time for improved in vitro analyses.