| A biosensor for bacterial detection was developed based on microelectromechanical systems (MEMS), heterobifunctional crosslinkers and immobilized antibodies. The sensor detected the change in impedance caused by the presence of bacteria immobilized on interdigitated gold electrodes. Fabricated from (100) silicon with a 2mum layer of thermal oxide as an insulating layer, the sensor active area was 9.6mm2 and consisted of two interdigital gold electrode arrays each measuring 0.8mm x 6mm. Escherichia coli specific antibodies were immobilized to the silicon oxide between the electrodes to create a biological sensing surface. The electrical impedance across the interdigital electrodes was measured at frequencies between 100Hz to 10MHz after immersing the biosensor in a neutral buffer. Bacterial cells present in the sample solution attached to the antibodies and became tethered to the sensor surface thereby causing a change in measured impedance. The biosensor was tested using pathogenic and non-pathogenic E. coli strains and was able to discriminate between different cellular concentrations from 105--107 CFU/mL (colony-forming units per milliliter) in pure culture. The design, fabrication and testing of the biosensor is discussed along with the implications of these findings towards developing a biosensor for the detection of foodborne pathogens. |
