Use of Protein Engineering to Elucidate Electron Transfer Pathways between Proteins and Electrodes

Peroxidase-like Nanoparticles of Noble Metals Stimulate Increasing Sensitivity of Flavocytochrome b2-Based L-Lactate Biosensors

We report the development of amperometric biosensors (ABSs) employing flavocytochrome b2 (Fcb2) coupled with nanoparticles (NPs) of noble metals on graphite electrode (GE) surfaces. Each NPs/GE configuration was evaluated for its ability to decompose hydrogen peroxide (H2O2), mimicking peroxidase (PO) activity. The most effective nanoPO (nPO) was selected for developing ABSs targeting L-lactate. Consequently, several Fcb2/nPO-based ABSs with enhanced sensitivity to L-lactate were developed, demonstrating mediated ET between Fcb2 and the GE surface. The positive effect of noble metal NPs on Fcb2-based sensor sensitivity may be explained by the synergy between their dual roles as both PO mimetics and electron transfer mediators. Furthermore, our findings provide preliminary data that may prompt a re-evaluation of the mechanism of L-lactate oxidation in Fcb2-mediated catalysis. Previously, it was believed that L-lactate oxidation via Fcb2 catalysis did not produce H2O2, unlike catalysis via L-lactate oxidase. Our initial research revealed that the inclusion of nPO in Fcb2-based ABSs significantly increased their sensitivity. Employing other PO mimetics in ABSs for L-lactate yielded similar results, reinforcing our hypothesis that trace amounts of H2O2 may be generated as a transient intermediate in this reaction. The presence of nPO enhances the L-lactate oxidation rate through H2O2 utilization, leading to signal amplification and heightened bioelectrode sensitivity. The proposed ABSs have been successfully tested on blood serum and fermented food samples, showing their promise for L-lactate monitoring in medicine and the food industry.

Expanding the Genetic Code of Bioelectrocatalysis and Biomaterials

Genetic code expansion is a promising genetic engineering technology that incorporates noncanonical amino acids into proteins alongside the natural set of 20 amino acids. This enables the precise encoding of non-natural chemical groups in proteins. This review focuses on the applications of genetic code expansion in bioelectrocatalysis and biomaterials. In bioelectrocatalysis, this technique enhances the efficiency and selectivity of bioelectrocatalysts for use in sensors, biofuel cells, and enzymatic electrodes. In biomaterials, incorporating non-natural chemical groups into protein-based polymers facilitates the modification, fine-tuning, or the engineering of new biomaterial properties. The review provides an overview of relevant technologies, discusses applications, and highlights achievements, challenges, and prospects in these fields.

Living electronics: A catalogue of engineered living electronic components

Biology leverages a range of electrical phenomena to extract and store energy, control molecular reactions and enable multicellular communication. Microbes, in particular, have evolved genetically encoded machinery enabling them to utilize the abundant redox-active molecules and minerals available on Earth, which in turn drive global-scale biogeochemical cycles. Recently, the microbial machinery enabling these redox reactions have been leveraged for interfacing cells and biomolecules with electrical circuits for biotechnological applications. Synthetic biology is allowing for the use of these machinery as components of engineered living materials with tuneable electrical properties. Herein, we review the state of such living electronic components including wires, capacitors, transistors, diodes, optoelectronic components, spin filters, sensors, logic processors, bioactuators, information storage media and methods for assembling these components into living electronic circuits.

Enzymatic and Microbial Electrochemistry: Approaches and Methods

The coupling of enzymes and/or intact bacteria with electrodes has been vastly investigated due to the wide range of existing applications. These span from biomedical and biosensing to energy production purposes and bioelectrosynthesis, whether for theoretical research or pure applied industrial processes. Both enzymes and bacteria offer a potential biotechnological alternative to noble/rare metal-dependent catalytic processes. However, when developing these biohybrid electrochemical systems, it is of the utmost importance to investigate how the approaches utilized to couple biocatalysts and electrodes influence the resulting bioelectrocatalytic response. Accordingly, this tutorial review starts by recalling some basic principles and applications of bioelectrochemistry, presenting the electrode and/or biocatalyst modifications that facilitate the interaction between the biotic and abiotic components of bioelectrochemical systems. Focus is then directed toward the methods used to evaluate the effectiveness of enzyme/bacteria-electrode interaction and the insights that they provide. The basic concepts of electrochemical methods widely employed in enzymatic and microbial electrochemistry, such as amperometry and voltammetry, are initially presented to later focus on various complementary methods such as spectroelectrochemistry, fluorescence spectroscopy and microscopy, and surface analytical/characterization techniques such as quartz crystal microbalance and atomic force microscopy. The tutorial review is thus aimed at students and graduate students approaching the field of enzymatic and microbial electrochemistry, while also providing a critical and up-to-date reference for senior researchers working in the field.

Electrodetection of Small Molecules by Conformation-Mediated Signal Enhancement

Electrochemical biosensors allow the rapid, selective, and sensitive transduction of critical biological parameters into measurable signals. However, current electrochemical biosensors often fail to selectively and sensitively detect small molecules because of their small size and low molecular complexity. We have developed an electrochemical biosensing platform that harnesses the analyte-dependent conformational change of highly selective solute-binding proteins to amplify the redox signal generated by analyte binding. Using this platform, we constructed and characterized two biosensors that can sense leucine and glycine, respectively. We show that these biosensors can selectively and sensitively detect their targets over a wide range of concentrations-up to 7 orders of magnitude-and that the selectivity of these sensors can be readily altered by switching the bioreceptor's binding domain. Our work represents a new paradigm for the design of a family of modular electrochemical biosensors, where access to electrode surfaces can be controlled by protein conformational changes.

Protein engineering for electrochemical biosensors

The development of electrochemical biosensors has gained tremendous attention. Protein engineering has been applied for enhancing properties of native redox enzymes, such as selectivity, sensitivity, and stability required for applicable biosensors. This review highlights recent advances of protein engineering to improve enzymatic catalysis of biosensors, facilitate electron transfer and enzyme immobilization, and construct allosteric protein biosensors. The pros and cons of different protein engineering strategies are briefly discussed, and perspectives are further provided.