| Photoelectrochemical(PEC)bioanalysis is a new method for biomolecule detection,which combined the advantages of photoelectrochemical process and biometric identification process.The direct electron transfer between the target and the photoactive material is used to generate the change of photocurrent signal,and realize the quantitative detection of the target.With the increasing demand for sensitive in biological analysis,high photoelectric conversion efficiency and effective signal amplification strategy are particularly important for PEC immunoanalysis.Therefore,looking for highly efficient photoactive materials,introducing simple and efficient signal amplification strategy,and exploring new sensor recognition system will always be the research focus of biological analysis of PEC.In this paper,bismuth sulfide nanometer heterojunction materials with excellent photoelectric properties were synthesized.Combined with enzyme-assisted redox cycle signal amplification strategy,photoelectric chemical immunesensing platform and self-powered photoelectric chemical immunesensing platform were constructed for the analysis and detection of disease-related biomarkers.The main innovations and research contents are as follows:1.A novel photoelectrochemical(PEC)immunoassay for ultrasensitive detection of Interleukin-6(IL-6)were designed based on a direct Z-scheme Bi2S3/Bi2MoO6heterojunction,intergating with the photogenerated hole-induced chemical redox cycling amplification(RCA)strategy.Firstly,the Z-scheme heterostructure materials with biomimetic structure were constructed via a classic hydrothermal method,and then modified on the ITO electrode.The Z-scheme heterojunction can greatly improve the spatial separation of photogenerated charge carriers,and increases light harvesting,and then generate higher photocurrent signals.At the same time,the enzyme-catalyzed redox cycling was found to enhance the PEC signal,thus multiple-enhanced photoanodic PEC bioassay was realized.Moreover,the designed immunosensor was successfully applied for IL-6 determination in human serums with a wide liner range from 5.0×10-14 to 1.0×10-8 g/mL,and a detection limit of 2.0×10-14 g/mL(S/N=3).The immunosensor was applied to the detection of IL-6 in human serum samples,and the recovery was between 90.0%–110.0%.2.Herein,an ingenious visible light-induced membraneless self-powered PEC biosensing platform was constructed,integrating a signal amplification strategy for ultrasensitive split-type myoglobin(Myo).The system was comprised of a Bi2S3/BiPO4heterojunction photoanode and Pt cathode in a one compartment chamber,which Myo was used as the target protein.Firstly,a model protein an alkaline phosphatase(ALP)-loaded sandwich immunoassay to generated the signal reporter ascorbic acid(AA)in a 96-well plate.Secondly,the chemical-chemical redox cycling scheme was operated upon the initial oxidation of Fc by the holes in the Bi2S3/BiPO4 photoelectrode,Fc could be regenerated from Fc+by the AA.Subsequently,AA could be regenerated by TCEP after its oxidation,the cycling was triggered.Then the enzymatic generation of AA was transferred into the solution containing ferrocene(Fc)and Tris(2-carboxyethyl)phosphine(TCEP)for PEC detection.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.In addition,the designed method was applied to the determination of Myo in human serum samples.The results were nearly consistent with the reference values of Xinyang Central Hospital.The recoveries of 89.0%to 110.0%,and the RSDs were no more than 5.6%.This work provides light on the design of redox cycling strategy in the self-powered PEC biosensor,and also provides an effective approach for clinical diagnosis of disease.3.The feasibility of chemical-chemical redox cycling on the photocathode was explored,and a self-powered PEC biosensors was constructed by separating the photoanode from biometric events,and the sensor has demonstrated excellent sensitivity and resistance to interference by reducing substances.The system was consisted of a Bi2S3/Bi3TaO7 heterojunction photoanode and a CuInS2 microflowers photocathode in separated chambers.Using Interleukin-6(IL-6)as a model protein,the signal reporter4-aminophenol(AP)was generated by the alkaline phosphatase(ALP)label of a sandwich immunoreaction.Upon the generated AP was transferred into the solution containing Ag+and?-nicotinamide adenine dinucleotide reduced dipotassium(NADH)on the surface of CuInS2 microflowers photocathode,the chemical-chemical redox cycling was triggered.Meanwhile,due to large amount of Ag deposition on the photocathode,the photocurrent response was enhanced for the self-powered system.The combination of the chemical-chemical redox cycling on the photocathode with the enzymatic amplification endowed the PEC biosensing system with high selectivity and sensitivity for IL-6 detection.The immunoassay exhibited a low detection limit of 2.0×10-14 g/mL with a wide linear range of 5.0×10-14–1.0×10-8 g/mL.In addition,the method was employed to quantify the IL-6 content in human serum samples,the recoveries range from 86.0%to 110%,and the RSDs were no more than 7.9%.This work provided a new perspective for the design of advanced PEC biosensors and the application of chemical-chemical redox cycling amplification in PEC bioanalysis.4.An ingenious strategy of chemical redox cycle signal amplification was proposed,to amplify the signal,and a self-powered photochemical(PEC)sensing platform with photoanode and biometric event separation was contructed for colorimetric detection for heat shock protein 90a(HSP90a).The sensors system consists of a Z-Scheme Bi2S3/Bi2O3 photoanode and a NiO electrode.Under the visible light excitation,the photoelectrons generated by the photoanode will be transferred to the photocathode through the external circuit.In the presence of Hsp90a,the transfer rates of photoelectrons are slow due to steric hindrance,resulting in the different color rendering degree of Fe(BPT)32+.Enzyme-catalyzed chemical redox cycle system not only realizes colorimetric analysis,but makes the colorimetric signal significantly amplified.Moreover,the color intensity of Fe(BPT)32+was proportional to the concentration of Hsp90a,so we can carry out quantitative detection of Hsp90aaccording to the color intensity.The immunoassay exhibited a low detection limit of 1.0×10-14 g/mL with a wide linear range of 4.0×10-14–1.0×10-8 g/mL.The proposed method could provide a rapid and intuitive method for the detection of biological samples,which has great application prospects in the diagnosis of tumor markers. |
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