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 (C-60), 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/C-60 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-Ab(1)) through the covalent reaction between biotin and avidin. With surface area enhancement by C-60 and Au-SiO2, and directional immobilization by avidin biotin system, the amount of immobilized bio-Ab(1) can be enhanced obviously. For signal amplification, the glucose oxidase (GOD) loaded Pt nanochains (PtNCs) were used as tracing tag to label signal antibodies (Ab(2)). With a sandwich-type immunoreaction, the concentration volume of heat-killed E. coli O157:H7 ranged from 3.2 x 10(1) to 3.2 x 10(6) 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. (C) 2013 Elsevier B.V. All rights reserved.