Dual Functional Core-Shell Fluorescent Ag2S@Carbon Nanostructure for Selective Assay of E. coli O157:H7 and Bactericidal Treatment.

A dual functional fluorescent core-shell Ag2S@Carbon nanostructure is prepared by a hydrothermally assisted multi-amino synthesis approach with folic acid (FA), polyethylenimine (PEI), and mannoses (Mans) as carbon and nitrogen sources (FA-PEI-Mans-Ag2S nanocomposite shortly as Ag2S@C). The nanostructure exhibits strong fluorescent emission at λex/λem = 340/450 nm with a quantum yield of 12.57 ± 0.52%. Ag2S@C is bound to E. coli O157:H7 via strong interaction with the Mans moiety in Ag2S@C with FimH proteins on the fimbriae tip in E. coli O157:H7. Fluorescence emission from Ag2S@C/E. coli conjugate is closely related to the content of E. coli O157:H7. Thus, a novel procedure for fluorescence assay of E. coli O157:H7 is developed, offering a detection limit of 330 cfu mL-1. Meanwhile, the Ag2S@C nanostructure exhibits excellent antibacterial performance against E. coli O157:H7. A 99.9% sterilization rate can be readily achieved for E. coli O157:H7 at a concentration of 106-107 cfu mL-1 with 3.3 or 10 μg mL-1 of Ag2S@C with an interaction time of 5 or 0.5 min, respectively.