A Smartphone-Enabled Colorimetric Platform Based on Enzyme Cascade Amplification Strategy for Detection of Staphylococcus aureus in Milk

Staphylococcus aureus (S. 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 cascade bio-nanozyme formed by immobilized glucose oxidase (GOx) on the 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. S. aureus detection could be performed through naked-eye observation and smartphone measurement, 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.