Characterisation of a colourimetric biosensor SapYZUM13@Mn3O4-NH2 reveals the mechanisms underlying its rapid and sensitive detection of viable Staphylococcus aureus in food

In this study, a colourimetric biosensor based on bacteriophage SapYZUM13 and an aminated Mn 3 O 4 (Mn 3 O 4 -NH 2 ) nanozyme was constructed and evaluated for its ability to detect Staphylococcus aureus in food. The biosensor had a detection time of 20 min, with a detection limit of 2 × 10 1  CFU/mL and recovery rate of 92.42–106.96%, indicating its high reliability and accuracy in detecting the food pathogen . Mechanistically, SapYZUM13@Mn 3 O 4 -NH 2 exhibited oxidase-mimicking capability, producing O 2 •– free radicals which oxidise 3,3′,5,5′-tetramethylbenzidine (TMB) to yield blue-coloured oxTMB. In the presence of S. aureus , the oxidase activity decreased remarkably owing to shielding of the nanozyme active sites. Moreover, SapYZUM13@Mn 3 O 4 -NH 2 could detect viable S. aureus from various sources, likely because of the special receptor-binding proteins of SapYZUM13 adsorbing to the wall teichoic acids on the S. aureus cell surface. Thus, SapYZUM13@Mn 3 O 4 -NH 2 has broad application prospects for the detection of viable S. aureus in various foods.