Stepwise surface regeneration of electrochemical immunosensors working on biocatalyzed precipitation, Analyst 127

A new strategy of stepwise surface regeneration for electrochemical immunosensors, working on a biocatalyzed precipitation reaction, has been developed. The strategy is based on the combination of deposited product thin-film dissolution and bound-protein displacement reactions from the modified sensor surfaces. As a model system, surfaces functionalized with biotin groups and their affinity recognition/ displacement reactions with antibiotin antibody molecules were chosen and investigated for affinity-sensing and stepwise regeneration reactions

RhCu 3D Nanoframe as a Highly Active Electrocatalyst for Oxygen Evolution Reaction under Alkaline Condition

One pot synthesis of RhCu alloy truncated octahedral nanoframes, Cu@Rh core–shell nanoparticles, and a bundle of five RhCu nanowires is demonstrated. The RhCu alloy 3D nanoframe, in particular, exhibits excellent catalytic activity toward the oxygen evolution reaction under alkaline conditions. © 2015 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim113131sciescopu

Glucose-Oxidase Label-Based Redox Cycling for an Incubation Period-Free Electrochemical Immunosensor

Catalytic reactions of enzyme labels in enzyme-linked immunosorbent assays require a long incubation period to obtain high signal amplification. We present herein a simple immunosensing scheme in which the incubation period is minimized without a large increase in the detection limit. This scheme is based on electrochemical-enzymatic (EN) redox cycling using glucose oxidase (GOx) as an enzyme label, Ru­(NH₃)₆³⁺ as a redox mediator, and glucose as an enzyme substrate. Fast electron mediation of Ru­(NH₃)₆³⁺ between the electrode and the GOx label attached to the electrode allows high signal amplification. The acquisition of chronocoulometric charges at a potential in the mass transfer-controlled region excludes the influence of the kinetics of Ru­(NH₃)₆²⁺ electrooxidation and also facilitates high signal-to-background ratios. The reaction between reduced GOx and Ru­(NH₃)₆³⁺ is rapid even in air-saturated Tris buffer, where the faster competitive reaction between reduced GOx and dissolved oxygen also occurs. The direct electrooxidation of glucose at the electrode and the direct electron transfer between glucose and Ru­(NH₃)₆³⁺ that undesirably increase background levels occur relatively slowly. The detection limit for the EN redox cycling-based detection of cancer antigen 125 (CA-125) in human serum is slightly higher than 0.1 U/mL for the incubation period of 0 min, and the detection limits for the incubation periods of 5 and 10 min are slightly lower than 0.1 U/mL, indicating that the detection limits are almost similar irrespective of the incubation period and that the immunosensor is highly sensitive