Polydopamine nanospheres loaded with l-cysteine-coated cadmium sulfide quantum dots as photoelectrochemical signal amplifier for PSA detection

A sandwich-type photoelectrochemical (PEC) immunosensor was constructed for sensitive detection of prostate specific antigen (PSA). It was based on electrochemically reduced graphene oxide-TiO 2 (ERGO-TiO 2 ) as photoelectrochemical platform to immobilize capture antibody (Ab 1 ). Then, quinone-rich polydopamine nanospheres (PDANS) loaded detection antibody (Ab 2 ) and photocurrent signal label, l -cysteine-coated cadmium sulfide quantum dots (CdSQDs). ERGO-TiO 2 displayed greatly improved photocurrent response to white light. CdSQDs conjugated with PDANS further amplified photocurrent signal because of the good conductivity of PDANS and ERGO. The increased photocurrent showed a linear correlation with PSA in the concentration range from 0.02 pg mL −1 to 200 ng mL −1 with the detection limit of 6.8 fg mL −1 . It also revealed high selectivity and good stability.