Oligonucleotide-mediated the oxidase-mimicking activity of Mn3O4 nanoparticles as a novel colorimetric aptasensor for ultrasensitive and selective detection of Staphylococcus aureus in food

Colorimetric detection of pathogenic bacteria in food still faces many challenges. Herein, a novel label-free and ultrasensitive colorimetric aptasensor was firstly established for the detection of food-borne pathogenic like Staphylococcus aureus ( S. aureus ) based on oligonucleotide-mediated the oxidase-mimicking activity of octahedral Mn 3 O 4 nanoparticles (NPs). The study confirmed that the common oligonucleotide such as SA31 aptamer can adsorb on the surface of octahedral Mn 3 O 4 NPs, and significantly inhibit the oxidase-mimicking activity by blocking their electron transfer to 3,3′,5,5′-tetramethylbenzidine. In the presence of S. aureus , aptamers will preferentially bind to bacterial cell, resulting in the recovery of oxidase-mimicking activity. The naked eye can easily recognize the color change from green to yellow, with the increase concentration of S. aureus from 10 CFU·mL −1 to 2 × 10 5 CFU·mL −1 . The colorimetric aptasensor shows a low detection limit of 3 CFU·mL −1 (S/N = 3). This strategy has excellent selectivity whether the presence of other competitive bacteria, and has been successfully applied to the non-enrichment detection of S. aureus in milk and pork samples.