Aptamer-Driven Assembly of Enzyme Immobilization on Ag-HMPB@UiO-66 MOF-on-MOF Nanostructures for High-sensitivity Electrochemical Biosensing of Trichlorfon

Combining high-electroactive nanomaterial with enzyme immobilization, the development of the electrochemical biosensor is a frontier approach to improve the sensitivity and selectivity for the detection of organophosphorus pesticides (OPs). In this study, a core–shell nanostructure (Ag-HMPB@UiO-66) was prepared with the Ag-HMPB as a core and a UiO-66 forming the shell as an advanced platform for acetylcholinesterase (AChE) immobilization. The innovation lies in the synergistic integration of the excellent electron transfer capability of Ag-HMPB with the good structural stability of UiO-66. Based on Lewis acid–base theory, the form of Zr─O─P coordination bond could improve the efficiency of aptamer (Apt) immobilization (131.65 nM mg −1 ) compared with physical adsorption. Electrochemical analysis revealed that the as-prepared biosensor exhibited exceptional substrate affinity, with a low K m of 0.234 mM. Under optimized conditions, the biosensor exhibited sensitive detection of trichlorfon over a wide range (1 × 10 −13 to 2.5 × 10 −9 g L −1 ), with a low LOD of 0.44 pg L −1 (3σ/slope). Additionally, the biosensor can also be applied to the cucumber with good recovery (97.34% to 103.35%), as well as good storage stability and reproducibility. This provides a reliable and powerful tool for the trace detection of OPs in complex agricultural products.