Construction Of CdS-based Heterojunction Photoelectrochemical Biosensor And Detection Of Disease Markers

Some changes in the concentration of disease markers can reflect the health status of the human body,and achieving their highly sensitive detection is conducive to early diagnosis and treatment of diseases.Photoelectrochemistry(PEC)is a new detection technology based on electrochemistry,which has the advantages of high sensitivity,good selectivity,easy miniaturization,and is widely used in the detection of disease markers.However,PEC sensing still has some limitations,such as electrode materials have low photoelectric conversion efficiency,serious recombination of photogenerated carriers,and are susceptible to light corrosion.In order to solve these problems,the paper mainly works from the following three aspects:1.This work designed a novel MIP-PEC sensor based on CdS@ZnO heterostructure for detecting AFP.CdS@ZnO heterostructure were fixed on ITO electrode by electrochemical deposition and chemical deposition,respectively.The heterostructure can accelerate the spatial separation of electron-hole pairs,improve the absorption ability of visible light,and increase the photocurrent accordingly.With DA as the functional monomer and AFP as the template molecule,the MIP/CdS@ZnO/ITO can be synthesized by electropolymerization,in which MIP not only provided rich target recognition sites,but also can further enhance the system photocurrent.In addition,under the optimal experimental conditions,the sensor showed a wide linear range from 1 pg mL-1-1000 ng mL-1 and a low detection limit of 0.38 pg mL-1.The proposed MIP-PEC sensor had high sensitivity and excellent selectivity.The recovery rate of application in human serum ranged from 99.2%to 105.2%,which can be applied to early clinical diagnosis and biological analysis.2.SnO2/CdS@ZnO heterostructure was used as photoactive material,and aptamer was used as signal capture element.A labeled photoelectrochemical aptamer biosensor for quantitative detection of CEA was proposed.Because SnO2,ZnO,and CdS have a matching capable structure,and SnO2/CdS@ZnO heterostructure showed a higher photoelectric conversion efficiency.A simple unmarked aptamer PEC biosensor with high sensitivity and specificity was proposed for the quantitative detection of CEA.When the target CEA existed,the specific recognition and capture of the aptamer will lead to the increase of the spatial resistance of the photoelectrode and the quenching of the photocurrent,thus realizing the sensitive detection of CEA.Under the optimal conditions,the detection range of the PEC aptamer biosensor for CEA was 0.5 pg mL-1-100 ng mL-1,and the detection limit was 0.26 pg mL-1.The proposed PEC aptamer biosensor had good stability,sensitivity,repeatability,and can be applied to actual human serum analysis,showing a great application prospect in early clinical diagnosis.3.The photoelectrochemical/colorimetric dual-mode biosensor was constructed for thrombin detection based on CuZnS@CdS heterostructure.The matching energy levels of CuZnS and CdS can promote the separation of photogenerated electron holes,which showed good photoelectric properties.In photoelectrochemical sensing platform,the photocurrent quenching was caused by the steric hindrance of thrombin and the precipitation of 4-chloro-1-naphthol catalyzed by Hemin/G4 DNA2 mimetic enzyme.In the colorimetric sensing platform,the specific binding of thrombin to the aptamer resulted in the detachment of Hemin/G4 DNA2 mimetic enzyme.Using Hemin/G4 DNA2 simulated enzyme to catalyze the oxidation of OPD to produce DAP,it was observed that the color of the OPD solution changed from colorless to yellow.The linear relationship between thrombin concentration and absorbance was obtained through UV visible absorption spectroscopy.Using photoelectrochemistry and colorimetry to determine thrombin ensured the accuracy of results.Under optimal conditions,the linear range detected by the photoelectrochemical sensor was 1 fM to 100000 fM,with a detection limit as low as 0.36 fM.The linear range detected by the colorimetric sensor was 10 fM to 100000 fM,with a detection limit of 2.23 fM.The dual-mode sensor had been proved to be suitable for the accurate determination of thrombin in human serum.