Peptide-mediated binding of gold nanoparticles to E. coli for enhanced microbial fuel cell power generation
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Research Letter
Peptide-mediated binding of gold nanoparticles to E. coli for enhanced microbial fuel cell power generation Justin P. Jahnke, Hong Dong, Deborah A. Sarkes, James J. Sumner, Dimitra N. Stratis-Cullum, and Margaret M. Hurley, Army Research Laboratory, 2800 Powder Mill Road, Adelphi, MD 20783, USA Address all correspondence to Justin P. Jahnke at [email protected] (Received 28 February 2019; accepted 6 June 2019)
Abstract The authors demonstrate that gold-binding peptides displayed on the outer membrane of Escherichia coli enhance bioelectrochemical charge transfer by binding gold nanoparticles. Microbial fuel cells were run with different gold-binding peptides displayed and with different nanoparticle sizes, and the results were correlated with transmission electron microscopy (TEM) imaging of nanoparticle binding. When a goldbinding peptide is displayed and 5 nm gold nanoparticles are present, up to 4× power generation over E. coli not displaying a gold-binding peptide is observed. While an enhanced current is observed using the previously published M6G9, the largest enhancement is observed when a new longer peptide named M9G18 is used.
There has been considerable interest in facilitating electron transfer between electrodes and microorganisms to create bioelectrochemical systems. Such electron transfer can be used to break down organic matter in streams such as waste water to generate power,[1,2] to synthesize biologic molecules from inorganic carbon,[3] and to transmit signals between microorganisms and electrodes, both for sensing and for triggering cell responses.[4,5] While some organisms have intrinsic electron transfer capabilities, many organisms have only limited capabilities and, in general, intrinsic electron transfer rates are slow, which have led to employing material science and chemistry approaches to alter either microorganisms or electrode properties to enhance this transfer. Chemical approaches include the addition of membrane-permeabilizing stains[6,7] and the use of soluble redox mediators.[8] The electrode can also be modified to promote charge transfer, either by attaching functional groups[9] or by structuring it through the immobilization of, for example, nanoparticles on its surface.[10,11] Nanoparticles can also be attached to the microbes rather than the electrode.[12,13] High enough densities of nanoparticles may provide conduction paths for cells distant from the electrodes, but even lower densities of nanoparticles can serve to permeabilize the cell membrane, and the release of additional redox active molecules promotes charge transfer.[14] Nanoparticle interactions can be controlled in many ways. Many nanoparticle functionalizations exist to have either nonspecific (e.g., electrostatic)[15] or specific interactions (e.g., ligand binding).[16] Alternatively, the microbe can be engineered to controllably display moieties to bind the nanoparticles. A number of intrinsic mechanisms can be modified to control adhesion, including membrane-embedded proteins,
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