Mannan oligosaccharide-S. typhimurium interaction mediated fluorescent-recovery of carbon dots/molybdenum disulfide probe for rapid detection.

The rapid detection of Salmonella is an essential precautionary measure to ensure food safety and prevent foodborne illness. In this study, based on the specific binding between mannan oligosaccharides (MOS) and type I fimbriae of Salmonella typhimurium (S. typhimurium), an efficient sensing strategy was developed. Obtained by enzymatic hydrolysis of konjac glucomannan, MOS were grafted to mannan-oligosaccharide modified carbon dots (g-CDs-MOS). It is worth noting that the introduction of MOS reduced the dissociation constant (KD) between fabricated g-CDs-MOS and Con A from 25.4 µM (g-CDs and ConA) to 6.22 µM. This enhanced binding affinity stem from elevated density of MOS on surface of g-CDs. Furthermore, to construct recovery-type fluorescent probe, g-CDs-MOS was bonded onto two-dimensional quencher such as 3-aminobenzeneboronic acid-functionalized graphene oxide (GO-PBA), MnO2 or MoS2. The g-CDs-MOS/MoS2 exhibited the best sensitivity due to the high electron mobility of MoS2. Its fluorescent intensity was logarithmically responsive to concentration of S. typhimurium within the range of 102-108 CFU·mL- 1, and the corresponding limit of detection was as low as 11.79 CFU·mL- 1. This fluorescent sensor shows promise for the detection of S. typhimurium in food safety.