MOF-Integrated Single-Enzymatic Colorimetric Paper-Based Biosensor for Point-of-Care Testing of Organophosphorus Pesticides

Organophosphorus pesticides (OPs), which are widely applied in agriculture, raise significant environmental and health concerns due to their neurotoxic inhibition of acetylcholinesterase (AChE). Conventional point-of-care testing (POCT) methods for OPs, which are essential for food and environmental safety, commonly rely on multiple enzymes to generate a colorimetric signal. By integrating AChE and a colorimetric reagent into a metal-organic framework (MOF)-based paper chip (AA@ZIF@Paper) and simplifying the detection mechanism to a single enzymatic reaction with peroxidase-like acetylcholine (ATCI, the substrate of AChE), a highly sensitive, selective, and stable paper chip for POCT of OPs was developed. AA@ZIF@Paper demonstrated a linear range of 0.5-50 μg/L for the detection of dichlorvos within 20 min, with a low limit of detection (LOD) of 0.29 μg/L (S/N = 3). The encapsulation of AChE by MOF improved pH, temperature, and long-term storage stability, and the innovative utilization of peroxidase-like ATCI eliminated the use of multiple enzymes that may complicate detection and hinder reproducibility. Furthermore, a 3D-printed device and a smartphone application were developed to further enhance convenience and accuracy. This MOF-integrated single-enzymatic paper chip achieved instrument-free, portable, and convenient POCT for OPs, providing a promising platform for food safety control as well as environmental monitoring.