A smartphone-enabled colorimetric platform based on enzyme cascade amplification strategy for detection of...

Staphylococcus aureus is a pathogenic bacterium contaminating milk and dairy foods causing food poisoning and foodborne pathogens. In this work, a smartphone-enabled enzyme cascade-triggered colorimetric platform was constructed using a cascade bio-nanozyme formed by immobilized glucose oxidase (GOx) on Fe₃O₄@Ag for rapid detection of S. aureus. Benefiting from reasonable experimental design, a bio-nanozyme cascade-triggered reaction was achieved through H₂O₂ produced by GOx oxidation of glucose, followed by in situ catalysis of 3,3',5,5'-tetramethylbenzidine (TMB) by the inherent peroxidase-like activity of Fe₃O₄@Ag to produce color signals. Staphylococcus aureus detection could be performed through naked-eye observation and smartphone measurement, and the developed assay can achieve quantitative and qualitative detection of S. aureus. The on-site nanoplatform had satisfactory specificity and sensitivity with a low detection limit of 6.9 cfu·mL^-1 in 50 min. Moreover, the nanoplatform has good practicality in the detection of S. aureus in milk samples. Therefore, the assay has potential application prospects in food safety inspection.