Integrating Bacteriophage onto the Magnetic Nanozyme for Effective Enrichment and Colorimetric Detection of in Powdered Infant Formula.

is a dangerous pathogen easily found in powdered infant formula (PIF), causing severe infections and even death in infants. Herein, a bacteriophage-immobilized magnetic nanozyme (FeO@EspYZU13) was prepared for detection. Bacteriophage EspYZU13 isolated and identified by our group exhibits specific lytic capacity. FeO@EspYZU13 possesses remarkable enrichment capacity towards , efficiently enriching different concentrations of from a mixed bacterial solution. Furthermore, FeO@EspYZU13 shows peroxidase-like activity, which can catalyze the 3,3',5,5'-tetramethylbenzidine (TMB) chromogenic reaction in the presence of HO. Upon introduction of , it can be specifically captured by FeO@EspYZU13, inhibiting its peroxidase-like activity. Based on it, ranging from 3.2 × 10 to 3.2 × 10 CFU mL can be determined, offering a detection limit (LOD) of 26 CFU mL. Moreover, this reaction system keeps high specificity towards , which can resist interferences of other possible coexisting bacteria. in the artificially contaminated PIF can be detected, offering good recoveries (96.76% to 103.13%). These results indicate that our proposed reaction system demonstrates its practical application potential for efficient enrichment of from complex samples and accurate determination of in PIF.