MOF-818 nanozyme-based biosensor for specific point-of-care testing of Bacillus subtilis in complex agricultural soil

Bacillus subtilis (BS) effectively suppresses soilborne pathogens and enhances crop resistance through various mechanisms. However, its efficacy is significantly influenced by effective inter-root colonization rates, among other factors, necessitating precise quantitative monitoring for optimal application. Conventional detection methods are often time-consuming and technically demanding, limiting their application in the field. To address this challenge, we developed a dual-recognition biosensing platform. Specifically, tridentate-functionalized aptamer was utilized for rapid BS enrichment and secondary recognition achieved using fragment crystallizable mannose-binding lectin (FcMBL)-modified nanozyme (MOF-818). The rigid scaffold of MOF-818 ensured superior catechol oxidase activity and environmental stability, facilitating sensitive and robust online quantification of BS in complex soil matrices. The linear detection range of the platform was 10²-10⁷ CFU/mL, and the detection limit was 12 CFU/mL. This work provides a reliable tool for real-time monitoring of BS in agricultural systems, facilitating its efficient use in biocontrol and soil health management.