Immunoanalysis of E. coli O157:H7 based on Au nanoparticles labelling antibody using SPR biosensor

The anti-E. coli O157 : H7 polyclonal antibodies (PAb) were labelled with Au nanoparticles (AuNPs), which was used as secondary antibodies. The PAb, which was used as primary antibodies, was immobilized on the sensor surface with amino coupling method. The E. coli O157 : H7 was detected using direct assay and enhancing sandwich assay based on the two channels surface plasmon resonance (SPR) biosensor. The result indicated a good linear relationship between the SPR signal and logarithmic value of E. coli O157 : H7 concentration ranging from 10(3) cfu/mL to 10(9) cfu/mL, with the limit of detection (LOD) of 10(3) cfu/mL for the direct assay. For AuNPs enhancing sandwich assay, the linear range and the limit of detection were determined to be 10-10(10) cfu/mL and 10 cfu/mL, respectively. The sensitivity is 100 times higher than that of direct detection. By introducing AuNPs-PAb compound, a wider detection range and lower detection limit could be obtained. This method is rapid, and has good selectivity and reproducibility.