Browsing by Author "Campbell, Ian"

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    Solution-Deposited and Patternable Conductive Polymer Thin-Film Electrodes for Microbial Bioelectronics
    (Wiley, 2022) Tseng, Chia-Ping; Liu, Fangxin; Zhang, Xu; Huang, Po-Chun; Campbell, Ian; Li, Yilin; Atkinson, Joshua T.; Terlier, Tanguy; Ajo-Franklin, Caroline M.; Silberg, Jonathan J.; Verduzco, Rafael
    Microbial bioelectronic devices integrate naturally occurring or synthetically engineered electroactive microbes with microelectronics. These devices have a broad range of potential applications, but engineering the biotic–abiotic interface for biocompatibility, adhesion, electron transfer, and maximum surface area remains a challenge. Prior approaches to interface modification lack simple processability, the ability to pattern the materials, and/or a significant enhancement in currents. Here, a novel conductive polymer coating that significantly enhances current densities relative to unmodified electrodes in microbial bioelectronics is reported. The coating is based on a blend of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) crosslinked with poly(2-hydroxyethylacrylate) (PHEA) along with a thin polydopamine (PDA) layer for adhesion to an underlying indium tin oxide (ITO) electrode. When used as an interface layer with the current-producing bacterium Shewanella oneidensis MR-1, this material produces a 178-fold increase in the current density compared to unmodified electrodes, a current gain that is higher than previously reported thin-film 2D coatings and 3D conductive polymer coatings. The chemistry, morphology, and electronic properties of the coatings are characterized and the implementation of these coated electrodes for use in microbial fuel cells, multiplexed bioelectronic devices, and organic electrochemical transistor based microbial sensors are demonstrated. It is envisioned that this simple coating will advance the development of microbial bioelectronic devices.
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    Understanding and modulating electron transfer through ferredoxins
    (2020-04-23) Campbell, Ian; Silberg, Jonathon; Bennett, George
    Ferredoxins are a ubiquitous family of protein electron carriers that support electron transfer in a massive number of pathways across the tree of life. As central and ancient distributors of redox equivalents, they are advantageous targets for controlling electron flow and for studying the evolution of electron flux in cells. Herein, I describe my efforts to catalogue ferredoxins and their natural substitute, flavodoxins, from over 7000 organisms to understand the usage of protein electron carriers throughout the three domains. I apply my findings to study the distribution of cyanophage ferredoxins, focusing on the ferredoxin from a phage that infects the world’s most abundant phototroph. I demonstrate this viral Fd is unusually unstable yet presents a midpoint potential similar to bacterial homologs and can transfer electron to host oxidoreductases. When this viral Fd is recombined with a thermostable homolog, I am able to generate chimeric Fds with variable heat tolerances and potentials shifted by up to 50 mV that are capable of conducting electron transfer in vivo. Additionally, I will describe my efforts to reconstruct missing links in the evolution of [4Fe-4S] ferredoxins, demonstrating that symmetric ferredoxins and fragmented ferredoxins are capable of supporting electron transfer. These results expand our knowledge of natural ferredoxins and elucidate the design rules we might use to make synthetic variants.