A surface plasmon resonance enhanced photoelectrochemical immunoassay based on perovskite metal oxide@gold nanoparticle heterostructures.

An innovative visible light-driven photoelectrochemical (PEC) immunosensing system was reasonably established for the sensitive detection of prostate-specific antigen (PSA) by using perovskite metal oxide@gold nanoparticle heterostructures (BaTiO3/Au) as the photoactive materials. When plasmonic Au nanoparticles were directly decorated on BaTiO3, a several times surface plasmon resonance (SPR) enhancement of photocurrent density was induced via the injection of hot electrons from visible light-excited Au nanoparticles into the conduction band of BaTiO3, and the combination of BaTiO3 and Au nanoparticles was employed as a promising platform for developing a photoelectrochemical bioanalysis. As a proof of concept, PSA had been detected by the BaTiO3/Au nanocomposite-based PEC sensor. To design such an immunoassay protocol, a monoclonal anti-PSA capture antibody (cAb)-coated microplate and glucose oxidase/polyclonal anti-PSA detection antibody-modified gold nanoparticles (GOx-Au NP-dAb) were used as the immunoreaction platform and signal probe, respectively. Upon the addition of target PSA, a sandwiched immunocomplex was formed accompanying the immuno-recognition between the antigen and antibody, and then the carried GOx could oxidize glucose to produce H2O2. The photocurrent of the BaTiO3/Au nanocomposite-functionalized electrode amplified with increasing H2O2 concentration since H2O2 is considered as a good hole scavenger. On the basis of the above-mentioned mechanisms and the optimized conditions, the assembled PEC immunosensor was linear with the logarithm of the PSA concentration in the range of 0.01-40 ng mL-1 with a detection limit of 4.2 pg mL-1. It afforded rapid response, good precision, and high stability and specificity, implying its great promise in photoelectrochemical immunoassays. More generally, this system sets up an ideal PEC immunosensing system based on the BaTiO3/Au nanocomposites and represents an innovative and low-cost "signal-on" assay scheme for the practical quantitative screening of low-abundance proteins.