Self-assembled monolayers-based immunosensor for detection of Escherichia coli using electrochemical impedance spectroscopy

An electrochemical impedance immunosensor for the detection of Escherichia coli was developed by immobilizing anti-E. coli antibodies at n Au electrode. The immobilization of antibodies at the Au electrode was carried out through a stable acyl amino ester intermediate generated y 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) and N-hydrosuccinimide (NHS), which could condense antibodies reproducibly and ensely on the self-assembled monolayer (SAM). The surface characteristics of the immunosensor before and after the binding reaction of ntibodies with E. coli were characterized by atomic force microscopy (AFM). The immobilization of antibodies and the binding of E. coli cells o the electrode could increase the electro-transfer resistance, which was directly detected by electrochemical impedance spectroscopy (EIS) in he presence of Fe(CN)63−/Fe(CN)64− as a redox probe. A linear relationship between the electron-transfer resistance and the logarithmic value of . coli concentration was found in the range of E. coli cells from 3.0× 103 to 3.0× 107 cfu mL−1 with the detection limit of 1.0× 103 cfu mL−1. ith preconcentration and pre-enrichment steps, it was possible to detect E. coli concentration as low as 50 cfu/mL in river water samples. 2008 Elsevier Ltd. All rights reserved.