Homogeneous photoelectrochemical biosensor for sensitive detection of omethoate via ALP-mediated pesticide assay and Bi2S3@Bi2Sn2O7 heterojunction as photoactive material

A simple homogeneous photoelectrochemical (PEC) sensing platform based on an alkaline phosphatase (ALP)–mediated pesticide assay was established for the sensitive detection of omethoate (OM). The Bi2S3@Bi2Sn2O7 heterojunction was used as a photoactive material to provide stable background photocurrent signals. The inhibition of OM on ALP and PEC determination was carried out in the homogeneous system. In the absence of OM, dephosphorylation of L-ascorbic acid 2-phosphate trisodium salt (AAP) was catalyzed by ALP to produce the enzyme-catalyzed product (L-ascorbic acid, AA). AA, as an electron donor, could capture photogenerated holes on the Bi2S3@Bi2Sn2O7 heterojunction, thus inhibiting the recombination of electron holes to achieve an increase of the photocurrent signal. When the OM was introduced, the enzyme activity of ALP was reduced due to the organophosphorus pesticides (OPs)–based enzyme inhibition, and the AA produced by catalytic hydrolysis was also reduced, thus reducing the photocurrent signal. Compared with the traditional PEC sensor for OPs, this homogeneous PEC sensor avoided immobilization procedures, covalent labeling, separation, and the steric hindrance effect caused by immobilized biomolecules, which achieved high recognition efficiency and caused a reduction in analysis time. Additionally, an ALP-mediated pesticide assay for the determination of OPs with a simplified experimental process further improved the stability and reproducibility of the PEC sensor. The PEC sensor showed high sensitivity to the target OM within a dynamic range of 0.05 ~ 500 ng mL−1, and the detection limit was 0.0146 ng mL−1. Additionally, the PEC biosensing system showed good selectivity and anti-interference ability, and exhibited a satisfactory result in spinach and mustard samples.Graphical abstractA homogeneous PEC biosensor based on ALP inhibition strategy was constructed for OM detection in vegetable samples via Bi2S3@Bi2Sn2O7 heterojunction as the photoactive substrate material