Wool keratin-based colorimetric detection of organophosphorus pesticides via a multi-enzyme cascade reaction

A simple and sensitive colorimetric method for organophosphorus pesticides (Ops) detection was proposed via a multi-enzyme cascade reaction. The coordination compound of wool keratin and Cu (WK-Cu) was synthesized by self-assembly and used as a key catalyst in the cascade reaction. The enzymatic kinetics curve was established to explore the catalytic property, and the obtained K_m and V_max proved that WK-Cu has a good peroxidase-like activity. Ops could inhibit acetylcholinesterase activity and trigger the multienzyme cascades process, resulting in an amplified response signal. The key conditions were optimized, such as enzyme-linked reaction time and the concentration of each reactant in Ops detection. The detection range of phoxim was 10-1000 µg/L with a detection limit of 2.31 µg/L. Compared with other colorimetric detections, the proposed method exhibited a wider detection range and a relatively lower detection limit. In addition, this colorimetric method showed good universality and anti-interference ability for the analysis of phoxim in apple, cabbage and cauliflower samples. Owing to these merits, the proposed method has a good application prospect in Ops detection.