Portable Colorimetric Sensor Based on DNA-Ag/Pt Bimetallic Nanozyme Sensing Kit for Quantitative Detection of Staphylococcus aureus

Utilizing the high specificity of nucleic acid aptamers toward Staphylococcus aureus (S. aureus) and the peroxidase-like activity of Ag/Pt nanoclusters (Ag/Pt NCs), this study developed a portable “DNA-nanozyme” sensing kit for rapid and quantitative bacterial detection. In this strategy, S. aureus was first captured by biotinylated aptamers immobilized on a streptavidin-coated microplate and then further recognized by aptamer-functionalized Ag/Pt NCs (DNA-Ag/Pt NCs), forming a sandwich-type sensing interface. The localized nanozyme probes efficiently catalyzed the chromogenic reaction of 3,3′,5,5′-tetramethylbenzidine (TMB) in the presence of hydrogen peroxide (H2O2), enabling both visual readout and quantitative absorbance analysis. The assay exhibits a linear dynamic range from 101 to 106 CFU mL−1, with a limit of detection as low as 2.4 CFU mL−1, and shows negligible cross-reactivity with non-target bacterial strains. This platform provides a robust and field-deployable tool for point-of-care bacterial detection and on-site food safety screening.