Photoelectrochemical Immunoassay Of Car-cinoembryonic Antigen Based On Chemical Etching And Surface Charge Regulation Of Photoactive Materials

Malignant tumors are one of the major diseases endangering human life and health.As a broad-spectrum tumor marker,carcinoembryonic an-tigen（CEA）can be used as an important indicator for screening and diag-nosing malignant tumors.Accurate and fast detection of CEA is of great significance in medical research and clinical applications.Photoelectro-chemical analysis as a newly developed method based on photoelectric conversion has a low background signal and high sensitivity.It is important to develop efficient analysis strategies for expanding the application of PEC analysis.In this thesis,two new analytical strategies,including chem-ical etching of active materials V₂O₅ nanosheets by small biomolecules ascorbic acid（AA）and surface charge regulation of active materials Cd S quantum dots（QDs）by metal ions Ca²⁺,have been developed,and sensi-tive PEC detection to CEA was achieved.The main contents are as follows:（1）Ultrathin V₂O₅ nanosheets were obtained by ultrasonic peeling method,and Cd S QDs were loaded on the surface of V₂O₅ nanosheets to form Cd S/V₂O₅ nanocomposites.Cd S/V₂O₅ as a new photoelectric mate-rial can show superior photocurrent to V₂O₅ nanosheets and Cd S QDs un-der visible-light irradiation because of the promoted photogenerated elec-tron-hole separation and the increased visible-light absorption.V₂O₅nanosheets can be etched by AA because of the reduction of V₂O₅ to V⁴⁺,and the photocurrent of Cd S/V₂O₅ modified photoelectrode decreases sig-nificantly after being etched by AA.Inspired by this phenomenon,a PEC immunoassay platform is constructed for CEA detection by using Cd S/V₂O₅ nanocomposite as the photoelectric material and AA-encapsulated liposome immunonanocapsules as labels.The linear detec-tion range for detecting CEA is from 0.5 pg m L^-1 to 1 ng m L^-1,with a detection limit of 0.1 pg m L^-1.（2）Hexametaphosphate ions（HMP）capped CdS QDs were prepared and used as photoelectric material.The photocurrent of Cd S@HMP QDs modified photoelectrode in Na₂SO₃ solution is significantly enhanced after the incubation of Cd S@HMP QDs with Ca²⁺.It is found that the negative charges on the surface of Cd S QDs decrease due to the complexation be-tween HMP and Ca²⁺,thereby weakening the electrostatic repulsion be-tween Cd S QDs and the hole scavancer(SO₃^2-)accordingly,resulting in a promoted electron-hole separation efficiency.Based on the PEC response of Cd S@HMP QDs modified photoelectrode to Ca²⁺,a photoelectrochem-ical immunoassay platform for the detection of CEA was constructed by using Ca CO₃ nanoparticles as labels.The linear detection range for detect-ing CEA is 0.005-50 ng m L^-1,with a detection limit of 0.001 ng m L^-1.