A multicolor sensing system for simultaneous detection of four foodborne pathogenic bacteria based on FeO/MnO nanocomposites and the etching of gold nanorods.

Food safety problems attributed to foodborne pathogenic bacteria seriously endanger human health and cause substantial economic losses. Novel assays for rapid and sensitive identification of foodborne pathogenic bacteria are highly desired. In this study, a multicolor sensing system has been established for simultaneous determination of four foodborne bacteria by exploiting oxidase mimicking activity of aptamer-functionalized manganese dioxide-coated ferriferrous oxide (apt-FeO/MnO) nanocomposites and oxTMB etching of gold nanorods (AuNRs). Apt-FeO/MnO nanocomposites were used as capture probes to recognize and capture specific bacteria. The captured bacteria blocked the catalytic sites of the magnetic conjugate, which inhibited the catalyzation of oxTMB and further reduced the etching of AuNRs. Consequently, the longitudinal shift of AuNRs decreased linearly with the increase of the concentration of bacteria ranging from 10 to 10 CFU mL. Instrumental detection limits for S. aureus, L. monocytogenes, E. coli O157:H7 and V. parahaemolyticus reached down to 1.3 CFU mL, 1.2 CFU mL, 1.3 CFU mL and 1.4 CFU mL, respectively. And their visual detection limit was as low as 10 CFU mL. The whole detection process only needs 40 min, suggesting that this method is promising in on-site detection of bacteria.