Photoelectrochemical Biosensing Analysis Based On Bismuth-Based Compounds

Photoelectrochemical?PEC?analysis,which is an analytical method based on the direct or indirect interaction between irradiated photoactive materials and analytes to cause changes in photocurrent signals.PEC analysis adopts excitation and detection signals of different energy forms,and has the advantages of high sensitivity,fast response,and low cost.The combination of PEC technology and biomolecular recognition process has great potential and practical value in biomolecule detection in the future,and has attracted the attention of many researchers.Photoactive materials are the key element to photocurrent generation and signal change in PEC analysis.Bismuth based compound materials as photoactive materials which have recently appeared and have good performance have attracted wide attention,and the anode bismuth based compound PEC sensor has developed rapidly.However,the PEC anode analysis mode can easily be interrupted by reducing substances in the system,which limits its wide application in biological detection.In contrast,the PEC cathodic analysis mode has the outstanding advantage of anti-interference capability from reductive agents.In this paper,the prospects of bismuth based compounds for PEC biosensor construction are discussed,and three types of bismuth based compound PEC cathodic sensor were developed to detect multiple targets.The major research contents are described as follows:1.Novel “label-free”photoelectrochemical ochratoxin A sensor based on target cyclic signal amplification strategyBased on the increase of the photocurrent of BiOI by potassium ferricyanide as an electron acceptor,a PEC cathode sensor for detecting ochratoxin A?OTA?was established.The double-stranded DNA?dsDNA?modified on the electrode surface produces steric hindrance and electrostatic repulsion at the interface,which reduces the flux of potassium ferricyanide on the electrode surface and reduces the photocurrent.In the presence of OTA,the recognition of aptamers in dsDNA and OTA results in the dissociation of dsDNA and further digestion by RecJ_f exonuclease on the electrode surface.OTA after exfoliation can re-integrate with dsDNA to achieve circular signal amplification.Eventually,the dsDNA on the electrode surface leaves the electrode,the flux of potassium ferricyanide increases,and the cathode photocurrent increases.In addition to the advantages of simple operation,good stability and high selectivity,this“signal-on”and“label-free”detection may be easily extended as a general basis for addressing numerous other targets of interest.2.High-throughput photoelectrochemical immunosensor constructed by electrode surface reaction enhanced cathode photocurrentCatechol?CA?can bind to Bi³⁺on the surface of BiOI to form the Bi-CA complex,which enhances the cathode photocurrent.In addition,tyrosinase?TYR?can catalyze the oxidation of phenol to generate CA in the presence of NADH.Based on this,a split-type cathode PEC sensor was designed for the determination of TYR activity,and TYR was used as a signal marker tracer to further establish an immunoassay system to achieve detection of E.coli O157:H7.This detection system effectively separates the biological reaction from the PEC detection,which not only avoids the influence of the immobilized biomolecule on the PEC signal transmission,but also improves the flux of the sensor and realizes more effective detection.3.Split-type photoelectrochemical sensor detection of glucose-6-phosphate and glucose-6-phosphate dehydrogenase based on surface-forming complexesGlucose-6-phosphate dehydrogenase?G6PD?catalyzes the dehydrogenation of the substrate glucose-6-phosphate?G-6-P?to generate NADPH.In the presence of NADPH,p-hydroxybenzoic acid hydroxylase?PHBH?can catalyze the oxygenation reaction of the substrate p-hydroxybenzoic acid?PHBA?to generate protocatechuic acid?PCA?.And the PCA can enhance the cathode photocurrent of the Bi₂O₃ electrode.Based on this phenomenon,the catalytic dehydrogenation reaction of G6PD was combined with the catalytic oxygenation reaction of PHBH to achieve sensitive detection of G-6-P and G6PD.This sensor has the advantages of convenient operation,good specificity and high sensitivity.The detection limits of G-6-P and G6PD are 2.0×10^-9 M and 2.5×10^-5 U/mL,respectively.