A facile and feasible photoelectrochemical (PEC) immunoassay based on plasmon-enhanced energy transfer between gold nanoparticles (AuNPs) and CdS quantum dots (QDs)/g-C3N4 nanosheets was developed for the ultrasensitive detection of lipoprotein-associated phospholipase A2 (Lp-PLA2). To construct such a sensing platform, the immunosensor was prepared by immobilizing Lp-PLA2 on a CdS QDs/g-C3N4-modified electrode. A competitive-type immunoreaction was utilized for Lp-PLA2 detection, with AuNP-labeled anti-Lp-PLA2 antibody used as the competitor. Introducing AuNPs with the specific antibody for the antigen target Lp-PLA2 led to heavy quenching of the photocurrent of CdS QDs/g-C3N4 due to the plasmon-enhanced energy transfer between AuNPs and CdS QDs. The quenching efficiency decreased with increasing target Lp-PLA2 concentration. Under optimal conditions, the PEC immunosensor presented a good photocurrent response to the target Lp-PLA2 in the dynamic linear range of 0.01-300 ng mL-1, with a low detection limit of 5.3 pg mL-1. Other biomarkers and natural enzymes did not interfere with response of this system. The reproducibility and accuracy of this method for the analysis of human serum specimens were evaluated, and the results given by the method developed here were found to closely correspond to the results obtained with commercial Lp-PLA2 ELISA kits. Importantly, this protocol offers promise for the development of exciton-plasmon interaction-based PEC detection systems. Graphical abstract ᅟ.
Keywords: CdS quantum dots/g-C3N4; Exciton–plasmon interaction; Gold nanoparticles; Lipoprotein-associated phospholipase A2; Photoelectrochemical immunosensor.