An electrochemical immunosensor for sensitive detection of Escherichia coli O157:H7 using C60 based biocompatible platform and enzyme functionalized Pt nanochains tracing tag

A sensitive and efficient electrochemical immunosensor was designed for amperometric detection of heat-killed Escherichia coli O157:H7 (E. coli O157:H7). The immunosensing platform was first composed of fullerene (C60), ferrocene (Fc) and thiolated chitosan (CHI-SH) composite nano-layer which could offer rich -SH functional groups and maintain good biocompatibility. Then the Au nanoparticles coated SiO2 nanocomposites (Au-SiO2) were assembled on the CHI-SH/Fc/C60 composite. Next, the large amount of avidin (SA) was coated on the Au-SiO2 surface, which was used to immobilize biotinylated capture antibodies of E. coli O157:H7 (bio-Ab1) through the covalent reaction between biotin and avidin. With surface area enhancement by C60 and Au-SiO2, and directional immobilization by avidin-biotin system, the amount of immobilized bio-Ab1 can be enhanced obviously. For signal amplification, the glucose oxidase (GOD) loaded Pt nanochains (PtNCs) were used as tracing tag to label signal antibodies (Ab2). With a sandwich-type immunoreaction, the concentration volume of heat-killed E. coli O157:H7 ranged from 3.2×101 to 3.2×106 CFU/mL with a limit of detection down to 15 CFU/mL (S/N=3), which could be well accepted for early clinical detection. The studied system provides new opportunities, and might speed up disease diagnosis, treatment and prevention with pathogen.