Colorimetric and Fluorescent Dual-Mode Detection of Multiple Pathogenic Bacteria by Horseradish Peroxidase @ Magnetic Zeolitic Imidazole Framework Biomineralization Composites

Rapid on-site pathogen detection is of paramount importance to prevent widespread bacterial infection. In this work, we successfully developed a dual-mode pathogen detection platform based on a horseradish peroxidase (HRP) @ magnetic zeolitic imidazole framework (HMZIF). By using HRP as a biotemplate and an optimal combination of ligand and salts, the HMZIF can be readily obtained through an innovative one-pot biomineralization process without incorporation of additional magnetic nanoparticles. Compared with the conventional magnetic MOF particles, HMZIFs have a smaller particle size (9.19 nm), a larger specific surface area, outstanding bacterial enrichment capability, superparamagnetic behavior, and enhanced peroxide catalysis activity. Then, a dual-mode detection platform integrating turn-off broad-spectrum colorimetric detection and a complementary turn-on specific fluorescent assay was developed by utilizing the high peroxidase activity and porous structure of the HMZIF. The presence of bacteria triggered the competitive desorption of glucose oxidase (GOD) from the HMZIF surface, thereby inhibiting the colorimetric cascade enzymatic reaction while simultaneously releasing the fluorescent dye (FAM) through aptamer-capped micropores. Under optimal conditions, the dual-mode platform exhibited detection limits of 870 and 2300 colony-forming units (CFU)/mL for Escherichia coli and Staphylococcus epidermidis in colorimetric modality and 28 and 16 CFU/mL in fluorescent modality, respectively. In practical applications, the fluorescence signal represents a specific pathogen concentration while the colorimetric signal indicates the total bacterial count. Thus, by using these two different types of detection modes, a comprehensive assessment of liquid quality safety can be conducted. This pathogen quantification platform was validated using real contaminated sewage and juice samples and provided a general technical route for detecting other pathogenetic bacteria by replacing a specific aptamer, making it a promising tool for monitoring and preventing bacterial infections in environmental and food contexts.