S‐Click Reaction for Isotropic Orientation of Oxidases on Electrodes to Promote Electron Transfer at Low Potentials

Electrochemical sensors are essential for point‐of‐care testing (POCT) and wearable sensing devices. Establishing an efficient electron transfer route between redox enzymes and electrodes is key for converting enzyme‐catalyzed reactions into electrochemical signals, and for the development of robust, sensitive, and selective biosensors. We demonstrate that the site‐specific incorporation of a novel synthetic amino acid (2‐amino‐3‐(4‐mercaptophenyl)propanoic acid) into redox enzymes, followed by an S‐click reaction to wire the enzyme to the electrode, facilitates electron transfer. The fabricated biosensor demonstrated real‐time and selective monitoring of tryptophan (Trp) in blood and sweat samples, with a linear range of 0.02–0.8 mm . Further developments along this route may result in dramatic expansion of portable electrochemical sensors for diverse health‐determination molecules.     

Light‐Triggered,Spatially Localized Chemistry by Photoinduced Electron Transfer

It is of immense interest to exert spatial and temporal control of chemical reactions. It is now demonstrated that irradiation can trigger reactions specifically at the surface of a simple colloidal construct, obtained by adsorbing polyethyleneimine on fluorescent colloidal particles. Exciting the fluorescent dye in the colloid affords photoinduced electron transfer to spatially proximal amine groups on the adsorbed polymer to form free radical ions. It is demonstrated that these can be harnessed to polymerize acrylic acid monomer at the particle surface, or to break up colloidal assemblies by cleaving a cross‐linked polymer mesh. Formation of free radical ions is not a function of the size of the colloid, neither is it restricted to a specific fluorophore. Fluorophores with redox potentials that allow photoinduced electron transfer with amine groups show formation of free radical ions.     

Interprotein Electron Transfer between FeS‐Protein Nanowires and Oxygen‐Tolerant NiFe Hydrogenase

Self‐assembled redox protein nanowires have been exploited as efficient electron shuttles for an oxygen‐tolerant hydrogenase. An intra/inter‐protein electron transfer chain has been achieved between the iron‐sulfur centers of rubredoxin and the FeS cluster of [NiFe] hydrogenases. [NiFe] Hydrogenases entrapped in the intricated matrix of metalloprotein nanowires achieve a stable, mediated bioelectrocatalytic oxidation of H₂ at low‐overpotential.