In Situ Optical Quantification of Extracellular Electron Transfer Using Plasmonic Metal Oxide Nanocrystals

• Published in: ChemElectroChem Vol. 9; no. 3
• Main Authors: Graham, Austin J., Gibbs, Stephen L., Saez Cabezas, Camila A., Wang, Yongdan, Green, Allison M., Milliron, Delia J., Keitz, Benjamin K.
• Format: Journal Article
• Language: English
• Published: United States ChemPubSoc Europe 11-11-2022
• Subjects: biosensors; colloidal semiconductor nanocrystals; electrochemistry; extracellular electron transfer; INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; localized surface plasmon resonance
• ISSN: 2196-0216; 2196-0216

Abstract
Extracellular electron transfer (EET) is a critical form of microbial metabolism that enables respiration on a variety of inorganic substrates, including metal oxides. However, quantifying current generated by electroactive bacteria has been predominately limited to biofilms formed on electrodes. To address this, we developed a platform for quantifying EET flux from cell suspensions using aqueous dispersions of infrared plasmonic tin‐doped indium oxide nanocrystals. Tracking the change in optical extinction during electron transfer enabled quantification of current generated by planktonic
Shewanella oneidensis
cultures. Using this method, we differentiated between starved and actively respiring cells, cells of varying genotype, and cells engineered to differentially express a key EET gene using an inducible genetic circuit. Overall, our results validate the utility of colloidally stable plasmonic metal oxide nanocrystals as quantitative biosensors in aqueous environments and contribute to a fundamental understanding of planktonic
S. oneidensis
electrophysiology using simple
in situ
spectroscopy.