Enzyme Inhibition-Mediated Distance-Based Paper Biosensor for Organophosphate Pesticide Detection in Food Samples

Organophosphate pesticides (OPs) enter the environment through various avenues, posing significant health risks. This highlights the need to monitor OPs in food and environmental samples. This study introduces an enzyme inhibition-mediated distance-based paper (EIDP) biosensor designed for naked-eye visual detection of OPs in food samples. We synthesized a copper alginate (Cu-Alg) hydrogel that traps water within the gel and restricts water flow on pH paper. When incubated with acetylcholinesterase (AChE) and acetylthiocholine (ATCh), the enzyme activity of AChE on ATCh generates thiocholine, which interacts with the Cu2+ ions in the gel. This interaction alters the gel’s 3D structure, releasing the trapped water onto the pH paper. Conversely, when AChE is exposed to OPs, its activity is inhibited, limiting the water flow from the gel. As a result, OPs are quantified by measuring the reduction in water flow distance within a linear range of 18 to 105 ng/mL, with a lower detection limit of 18 ng/mL. The EIDP biosensor exhibits high selectivity for OP detection and successfully analyzes OPs in pumpkin and rice samples, achieving percent recoveries ranging from 93% to 103%. This method offers a straightforward, portable, instrument-free, and cost-effective solution for detecting OPs in food samples.