Photoelectrochemical biosensing of disease marker on p-type Cu-doped ZnCdS based on RCA and exonuclease III amplification.

In this work, a new "signal-on" split-type photoelectrochemical (PEC) sensing platform for prostate-specific antigen (PSA) detection was successfully constructed using p-type Cu-doped ZnCdS as the photosensitive semiconductor material and target-triggered rolling circle amplification (RCA) for signal amplification. The signal derived from Cu-doped ZnCdS was amplified by hemin/G-quadruplex. Upon target PSA introduction, the aptamer-primer probe (apt-pri) was captured by capture antibody-conjugated magnetic bead (MB-mAb) to form the sandwiched MB-mAb/PSA/apt-pri. The complex could initiate the RCA reaction to produce a long single-stranded DNA that provided binding sites for G-rich DNA and to form long single-stranded DNA/G-quadruplex/hemin. Upon the addition of exonuclease III (Exo III), the hemin/G-quadruplex immobilized on the RCA long product could be released by the digestion of Exo III. The hemin/G-quadruplex complexes in this study were used as efficient electron acceptors to neutralize the photoelectrons generated from the semiconductor and hindered the recombination of charges, thus enhancing the photocurrent. Under the optimum conditions, the developed sensing system displayed a good analytical performance with a linear range of 0.05-40 ng mL PSA and a detection limit of 16.3 pg mL. Furthermore, good selectivity, high anti-interference ability, satisfactory reproducibility, and good accuracy were also achieved. These prominent analytical properties revealed that our strategy might be a potential and reliable tool for the detection of PSA.