Impedimetric Biosensor for the Rapid Detection of Escherichia coli O157:H7

Abstract

A biosensor for E. coli O157:H7 detection was developed which detected the change inimpedance caused by the presence of cells immobilized on interdigitated gold electrodes. Thesensor was fabricated from a 100 Silicon wafer with a 2m layer of SiO2 as an insulating layer. Thesensor active area contained interdigital gold electrodes deposited over the SiO2 usingphotolithographic processing methods. Analyte specific antibodies were immobilized to the SiO2 inbetween the electrodes creating a biological sensing surface. Using impedance spectroscopy, theimpedance across the interdigital electrodes was measured after immersing the biosensor insolution. Bacteria cells present in solution attached to antibodies and became tethered to the sensorsurface. Immobilized bacteria cells changed the dielectric constant of the media between theelectrodes thereby causing a change in measured impedance. The biosensor was able todiscriminate between different cellular concentrations from 102 - 107 CFU/mL in pure culture with adetection time of 5 minutes. The design, modeling, fabrication and testing of the biosensor isdiscussed along with the implications of these findings towards further biosensor development.