Enzyme immobilization-based multilayer colorimetric probe for enhanced detection of viable foodborne pathogens

Pathogenic bacterial infections pose a significant threat to human life, health, and socioeconomic development, with those arising from Salmonella typhimurium (S. typhimurium) being particularly concerning. Herein, we developed a highly efficient catalytic material based on an ultra-stable MOF-808 core modified with an amorphous ZIF-8 layer, enabling substantial loading of horseradish peroxidase (HRP) to form MOF-808@Z-HRP. The catalytic activity of MOF-808@Z-HRP is approximately 1.65 times that of free HRP and 3.09 times that of HRP immobilized on MOF-808 without ZIF-8. Moreover, MOF-808@Z-HRP retains over 85% catalytic activity across a pH range of 5.0-7.0 and within a temperature range of 25-60 °C. Using this probe in combination with magnetic nanoparticles and phage recognition, we constructed a biosensor for ultrasensitive detection of viable S. typhimurium. The biosensor exhibits a linear detection range from 10² to 10⁷ CFU/mL with a limit of detection as low as 35.5 CFU/mL, and the entire detection process can be completed in 48 min. The proposed biosensor enables specific, sensitive, and rapid detection of viable S. typhimurium and demonstrates excellent performance in real samples. This work addresses critical challenges in food safety monitoring and offers a promising solution for rapid on-site pathogen screening.