A membraneless self-powered photoelectrochemical biosensor based on Bi2S3/BiPO4 heterojunction photoanode coupling with redox cycling signal amplification strategy.

The photoelectrochemical (PEC) self-powered system has attracted great attention in disease detection. The determination of a simple and efficient approach for disease-related biomarkers is highly interesting and appealing. Herein, an ingenious visible light-induced membraneless self-powered PEC biosensing platform was constructed, integrating a signal amplification strategy for ultrasensitive split-type PEC bioanalysis. The system was comprised of a Bi2S3/BiPO4 heterojunction photoanode and a platinum (Pt) cathode in a one compartment chamber. An alkaline phosphatase (ALP)-loaded sandwich immunoassay was used to generate the signal reporter ascorbic acid (AA) in a 96-well plate, and myoglobin (Myo) was used as a model protein. In the presence of AA, ferrocene (Fc), and Tris (2-carboxyethyl) phosphine (TCEP), the chemical-chemical redox cycling scheme was operated upon the initial oxidation of Fc by the holes in the Bi2S3/BiPO4 photoelectrode, and Fc was regenerated from Fc+ by AA. Subsequently, AA was regenerated by TCEP after its oxidation, and cycling was triggered. As a result, the proposed self-powered PEC sensing exhibited excellent performance with a wide linear range from 5.0 × 10-13 to 1.0 × 10-7 g/mL, and a low detection limit of 2.0 × 10-13 g/mL for Myo. This work provided a new design of a redox cycling strategy in the self-powered PEC biosensor, and showed an effective approach for the clinical diagnosis.

Photogenerated Hole-Induced Chemical-Chemical Redox Cycling Strategy on a Direct Z-Scheme Bi2S3/Bi2MoO6 Heterostructure Photoelectrode: Toward an Ultrasensitive Photoelectrochemical Immunoassay.

To achieve high sensitivity for biomolecule detection in photoelectrochemical (PEC) bioanalysis, the ideal photoelectrode and ingenious signaling mechanism play crucial roles. Herein, the feasibility of the photogenerated hole-induced chemical-chemical redox cycling amplification strategy on a Z-scheme heterostructure photoelectrode was validated, and the strategy toward enhanced multiple signal amplification for advanced PEC immunoassay application was developed. Specifically, a direct Z-scheme Bi2S3/Bi2MoO6 heterostructure was synthesized via a classic hydrothermal method and served as a photoelectrode for the signal response. Under the illumination, the PEC chemical-chemical redox cycling (PECCC) among 4-aminophenol generated by the enzymatic catalysis from a sandwich immunoassay, ferrocene as a mediator, and tris (2-carboxyethyl) phosphine as a reducing agent was run on the Z-scheme Bi2S3/Bi2MoO6 heterostructure photoelectrode. Exemplified by interleukin-6 (IL-6) as the target, the applicability of the strategy was studied in a PEC immunoassay. Thanks to the multiple signal amplification originating from the high efficiency of the PECCC redox cycling system, the enzymatic amplification, and the fine performance of the Z-scheme Bi2S3/Bi2MoO6 heterostructure photoelectrode, the assay for IL-6 exhibits a very low detection limit of 2.0 × 10-14 g/mL with a linear range from 5.0 × 10-14 to 1.0 × 10-8 g/mL. This work first validates the feasibility of the PECCC redox cycling on the Z-scheme heterostructure photoelectrode and the good performance of the strategy in PEC bioanalysis. We envision that it would provide a new prospective for highly sensitive PEC bioanalysis on the basis of a Z-scheme heterostructure.

Chemical-chemical redox cycling amplification strategy in a self-powered photoelectrochemical system: a proof of concept for signal amplified photocathodic immunoassay.

A chemical-chemical redox cycling amplification strategy was introduced into a photocathodic immunosensing system. To prove the applicability of the method, a novel self-powered photochemical system by integrating the photoanode and photocathode was designed for protein analysis.

A potentiometric resolved photoelectrochemical system based on CdS nanowires and SnNb2O6 nanosheets: a case application for dual biomarker analysis.

A potentiometric resolved photoelectrochemical (PEC) system based on CdS nanowires and SnNb2O6 nanosheets was developed. To prove the applicability of this system in PEC multi-biomarker analysis, a label free PEC immunosensor for two cardiac biomarkers, myoglobin and cardiac troponin I, was constructed.

Ru(NH3)63+/Ru(NH3)62+-Mediated Redox Cycling: Toward Enhanced Triple Signal Amplification for Photoelectrochemical Immunoassay.

Herein we report an effective Ru(NH3)63+/Ru(NH3)62+-mediated photoelectrochemical-chemical-chemical (PECCC) redox cycling amplification (RCA) strategy toward enhanced triple signal amplification for advanced split-type PEC immunoassay application. Specifically, alkaline phosphatase (ALP) label was confined via a sandwich immunorecognition to convert 4-aminophenyl phosphate to the signal reporter 4-aminophenol (AP), which was then directed to interact with Ru(NH3)62+ as a redox mediator and tris (2-carboxyethyl) phosphine (TCEP) as reducing agent in the detection buffer. Upon illumination, the system was then operated upon the oxidation of Ru(NH3)62+ by the photogenerated holes on the Bi2S3/BiVO4 photoelectrode, starting the chain reaction in which the Ru(NH3)62+ was regenerated by Ru(NH3)63+-enabled oxidization of AP to p-quinoneimine, which was simultaneously recovered by TCEP. Exemplified by interleukin-6 (IL-6) as the analyte, the Ru(NH3)63+/Ru(NH3)62+-mediated, AP-involved PECCC RCA coupled with ALP enzymatic amplification could achieve triple signal amplification toward the ultrasensitive PEC IL-6 immunoassay. This protocol can be extended as a general basis for other numerous targets of interest. Besides, we believe this work could offer a new perspective for the further exploration of advanced RCA-based PEC bioanalysis.