The Preparation Of “Signal-off” Photoelectrochemical Immunosensors And The Application In Early Diagnosis Of Tumor

In recent years,due to the high incidence and high mortality of cancer,more and more attention has been paid to physical health problems.It is very important to realize the accurate and rapid qualitative and quantitative analysis of tumor biomarkers in the early diagnosis,curative effect monitoring and guiding treatment of human related diseases.Photoelectrochemical?PEC?sensors have attracted widespread attention due to their advantages of simple equipment,low cost and high sensitivity.This thesis focuses on the preparation of functional nanoparticles and the construction of a novel highly sensitive PEC sensor.It is dedicated to the sensitive detection of ovarian cancer markers CA125 and DNA methyltransferase?Dam MTase?activity.The details are summarized as follows:1.By using SiO₂@polydopamine?PDA?core-shell nanoparticles?NPs?as a quencher for a CdTe quantum dots?QDs?probe,a“signal-off”PEC immunosensor with boosted sensitivity was reported.Using the detection of CA125 as an example,the PEC immunosensor showed a detectable range of 1 mU·mL^-1 to 100 U·mL^-1 and an ultralow detection limit of 0.3 mU·mL^-1?S/N=3?,the most sensitive sensor for CA125 reported so far.The constructed PEC immunosensor also had high selectivity and good accuracy for detecting tumor markers.This work shows the great potential of SiO₂@PDA for boosting sensitivity in“signal-off”PEC clinical diagnosis.2.Similarly,a"signal-off"sandwich-type PEC immuosensor was constructed for DNA MTase activity detection based on the probe of Sb₂Se₃-graphene oxide?GO?nanocomposites and Au NPs quencher.Under the action of Dam MTase and Dpn I,the hairpin probe DNA?hDNA?was cleaved into single-stranded DNA?ssDNA?,which could be hybridized with Au NPs functionalized DNA?S1?to form an immune complex,thus significantly reducing the photocurrent.The changes of PEC signals were proportional to the amount of Dam MTase.The results showed that the constructed PEC sensor had good stability and selectivity,and provided a new technology for early warning and early diagnosis of diseases.