Robust Amorphous MOF-Based Aerogels Digital Biosensor for Sensitive Detection of Organophosphate Pesticides

Enzyme-based point-of-care (POC) biosensors offer rapid on-site detection capabilities; however, their practical deployment is fundamentally constrained by limited sensing stability. Enzyme immobilization strategies enhance sensing stability but often compromise the catalytic activity of enzyme, thereby constraining the POC biosensor performance. In this study, a robust aerogel digital biosensor (ADB) was constructed by embedding enzyme-mediated amorphous MOFs (AChE-AMOF) into a calcium (II)/alginate aerogel system for stable and precise on-site detection of organophosphate pesticides. The enzyme-mediated process perturbs the Zn²⁺ coordination environment and disturbs the orderly MOF-74 framework, producing a porous AChE-AMOF composite that facilitates substrate accessibility and mitigates conformational changes of the immobilized enzyme. Impressively, the amorphous AChE-AMOF exhibits a 2.2-fold higher catalytic activity than AChE loaded in the crystalline MOF structure. The combination of the AMOF architecture and the aerogel's porous network confers high stability on the ADB, enabling it to retain over 98% of its enzymatic activity for 50 days. Moreover, the output signal of ADB can be converted into digital information by an image algorithm, enabling precise quantification of paraoxon at the nanogram per millilitre level. This work provides a robust tool for accurate on-site pesticide detection and offers meaningful insights into the design of high-performance enzyme-based POC biosensors.