Sandwich-based Photoelectrochemical Bioassays Based On Low-toxicity Inorganic Semiconductor Complexes

Photoelectrochemical(PEC)bioanalysis was a novel analytical technique which developed based on combining photoelectrochemical(PEC)process and biological recognition.The absolute separation of the excitation source and detection signal can greatly reduce the background signals,wonderfully improving the sensitivity.In addition,compared with some traditional methods of bioanalysis,such as electrochemical measurement,fluoremetry,electrochemiluminescent detection,PEC bioanalysis has obvious merits of high sensitivity,low over-potential,simple equipment,easy operation,or convenient micromation and integration.The detection of disease markers(tumor markers such as CEA,human T cell lymphoblastic virus type II,etc.)is of great significance for clinical diagnosis.In addition,semiconductor materials have been widely used in the construction of biosensors due to their excellent optical and electrical properties and good biocompatibility.In this paper,we designed three types of sandwich photoelectrochemical bioanalytical platforms,which were based on the use of low toxicity inorganic semiconductor composites as photoelectrochemical active materials in collaboration with semiconductor tag to amplify photoelectric response.1.An innovative and ultrasensitive photoelectrochemical(PEC)bioanalysis strategy was designed based on the significantly enhanced photocathodic signal of bismuth oxyiodine microspheres/graphitic carbon nitride(BiOI/g-C3N4)composites.The cascade band-edge levels between g-C3N4 and BiOI microspheres promoted absorbance of visible light and accelerated efficient transfer of photoinduced electrons.Moreover,hypotoxic BiOI/g-C3N4 composites as photoelectrochemical active species could generate more effective electron-hole pairs than g-C3N4 or BiOI microspheres alone,leading to much improving PEC response for enhancing detection sensitivity.H2O2 acted as an electron acceptor,which inhibited photocorrosion of B1OI/g-C3N4 composites and recombination of electron-hole pairs in BiOI/g-C3N4 composites,resulting in further wonderful enhancement of PEC response and amplification of detection signal.After copper sulfide(CuS)nanoparticles(NPs)that could consume electron acceptors and hinder photogenerated hole and electron acceptor transfer were introduced to labeled signal antibodies,the variation of signal was amplified before and after addition of analyte,leading to ulteriorly promotion of detection sensitivity.Using carcinoembryonic antigen(CEA)as a model analyte,a novel PEC strategy for sandwich-type assay of tumor maker at-0.05 V under visible light excitation was developed,which exhibited a wide linear range from 10 fg·mL-1 to 10 ng·mL-1,low limit of detection of 5.3 fg·mL-1 and excellent specificity.Furthermore,the proposed method was successfully analyzed the level of CEA in human serum,indicating satisfactory accuracy and validating the feasibility.This work would not only extend the application of BiOI and g-C3N4 in PEC devices,but also have prospect in clinical diagnoses.2.In this work,a new PEC sandwich immunoassay was fabricated,which was based on hypotoxic BiOI/BiOCl composites coupled with signal amplification of AgI conjugated signal antibodies(Ab2-AgI).Specifically,the hypotoxic inorganic semiconductor BiOI/BiOCl was fitst utilized in PEC bioanalysis.Due to the matched energy levels between BiOI and BiOCl,the photoelectric response was more excellent than BiOI or BiOCl alone.Moreover,the Ab2-AgI conjugates were used as signal amplification elements via the specific antibody-antigen immunoreaction.In the presence of target Ag,on the one hand,the immobilized Ab2-AgI conjugates could evidently increase the steric hindrance of the sensing electrode and effectively obstruct the transfer of the photo-induced holes,on the other hand,AgI could competitively absorb exciting light and consume electron acceptors.Using carcinoembryonic antigen(CEA)as a model analyte,a novel PEC immunosensing platform for tumor maker at 0 V under visible light excitation was developed,which exhibited a low limit of detection of 4.9 fg·mL-1.Meanwhile,it also presented good specificity and stability and might open a new promising platform for the detection of other important biomarkers.3.A novel "signal-on" photoelectrochemical(PEC)biosensor for sensitive detection of DNA was constructed on the basis of the hypotoxic Fe2O3/g-C3N4 magnetic material and the amplification strategy of AgI-cDNA composites.In this protocol,construction process could be carried out in solution by the magnetic properties of the Fe2O3/g-C3N4 composites,it made the biometric process more complete,which not only improved the detection sensitivity,but also simplifed the process of biosensor.In addition,the matched bandgap between AgI and Fe2O3/g-C3N4 complexes facilitated electron transfer and enhanced the photoelectric response.This work uses the HTLV-? as a detection model,with a linear range of 50 fM-50 pM and a detection limit of 4.0 fM,demonstrating high sensitivity.Moreover,this biosensor also has good reproducibility and selectivity,which would provide a simple PEC biosensing platform for DNA detection.