Ultra-sensitive and label-free detection of Escherichia coli O157:H7 using graphene-based field effect transistor modified with heat-denatured casein

Abstract

Sensitive detection of Escherichia coli O157:H7 (E. coli O157:H7) in suspected water samples is critical for containing the water-borne outbreak, which may cause acute diarrhea and intestinal bleeding. Here, we reported an improved graphene-based field effect transistor modified with heat-denatured casein (GFET) for sensitively detecting E. coli O157:H7 in real water samples. The heat-denatured casein coated on the graphene surface was served as a probe linker to bind with the specific antibody of E. coli O157:H7, and as a blocker to avoid the interference signal arising from the non-specific adsorption between the graphene surface and impurities in real water samples. The GFET biosensor provided a wide concentration range of 1–107 CFU·mL−1 for cultured E. coli O157:H7 with a detection limit of 1 CFU·mL−1. This developed GFET biosensor can also discriminate E. coli O157:H7 from other interfering substances with a high selectivity. In addition, correlation analysis of the E. coli O157:H7 in real samples using the GFET biosensor were proved the high agreement with enzyme-linked immunosorbent assay. The mass-produced GFET biosensor can achieve ultra-sensitive and label-free detection for the E. coli O157:H7 in water sample, promising prospective environmental monitoring application in the future.