Photoelectrochemical-Chemical-Chemical Redox Cycling for Advanced Signal Amplification: Proof-of-Concept Toward Ultrasensitive Photoelectrochemical Bioanalysis.

Signal amplification is essential for ultrasensitive photoelectrochemical (PEC) bioanalysis. Exploration of the facile and efficient route for multiple signal amplification is highly appealing. Herein, we present the concept of photoelectrochemical-chemical-chemical (PECCC) redox cycling as an advanced signal amplification route and a proof-of-concept toward ultrasensitive PEC bioanalysis. The system operated upon the bridging between the enzymatic generation of signaling species ascorbic acid (AA) from a sandwich immunoassay and the PECCC redox cycling among the ferrocenecarboxylic acid as redox mediator, the AA, and the tris(2-carboxyethyl)phosphine as reducing agent at the Bi2S3/Bi2WO6 photoelectrode. Exemplified by myoglobin (Myo) as target, the proposed system achieved efficient regeneration of AA and thus signal amplification toward the ultrasensitive split-type PEC immunoassay. This work first exploited the PECCC redox cycling, and we believe it will attract more interest in the research of PEC bioassays on the basis of advanced redox cycling.