A microfabricated biosensor for detecting foodborne bioterrorism agents

A biosensor for the detection of pathogenic bacteria was developed for biosecurity applications. The sensor was fabricated using photolithography and incorporates heterobifunctional crosslinkers and immobilized antibodies. The sensor detected the change in impedance caused by the presence of bacteria immobilized on interdigitated gold electrodes and was fabricated from (100) silicon with a 2-μm layer of thermal oxide as an insulating layer. The sensor has a large active area of 9.6 mm² and consists of two interdigital gold electrode arrays each measuring 0.8 × 6 mm. Pathogenic Escherichia coli and Salmonella infantis were tested in serially diluted pure culture. Analyte specific antibodies were immobilized to the oxide between the electrodes to create a biological sensing surface. After immersing the biosensor in solution, the impedance across the interdigital electrodes was measured. Bacteria cells present in the sample solution attached to the antibodies and became tethered to the electrode array thereby causing a change in measured impedance. The biosensor was able to discriminate between different cellular concentrations from 10⁴ - 10⁷ CFU/mL (colony-forming units per milliliter) in solution. The sample testing process, including data acquisition, required 5 min. The design, fabrication, and testing of the biosensor is discussed along with the implications of these findings toward further biosensor development.