A novel visible-light driven photoelectrochemical immunosensor based on multi-amplification strategy for ultrasensitive detection of microcystin-LR.

An ultrasensitive photoelectrochemical (PEC) immunoassay based on multiple signal amplification strategy was fabricated for the detection of microcystin-LR (MC-LR). The CdS/TiO nanorod arrays (CdS/TiO NRAs) modified FTO electrode, which can weaken the self-oxidation by photogenerated holes of CdS nanoparticles, and limit the recombination of electron-hole pairs and broaden optical absorption of TiO NRAs, was used as a visible-light driven material to immobilize antigens. Then, FeO nanoparticles/polydopamine (FeO@PDA) was used as the carrier to load secondary antibody (Ab) and horseradish peroxidase (HRP), where FeO nanoparticles and HRP can synergistically accelerate the oxidation of 4-chloro-1-naphthol (4-CN) by HO to produce biocatalytic precipitation (BCP) on the surface of modified electrode. Due to the catalytic activity of FeO nanoparticles and HRP, the nonproductive absorption of HRP and the steric hindrance by BCP, the photocurrent change was amplified. The proposed PEC immunosensor can detect MC-LR in a range of 0.005-500 μg/L with a detection limit of 0.001 μg/L. Meanwhile, the PEC immunosensor exhibited high sensitivity, good stability, acceptable selectivity and reproducibility, indicating its potential application in environmental monitoring.