Mahmoud Almasri
University of Missouri, USA
Title: An impedance biosensor for accurate and rapid detection of foodborne
Biography
Biography: Mahmoud Almasri
Abstract
An impedance biosensor for rapid detection of low concentration Escherichia coli O157:H7 was designed, fabricated and tested. The biosensor has the following innovative features: (1) a focusing region consisting of ramped down vertical (electroplated) gold electrode pair made along with 45o tilted thin film finger pairs. This configuration generates p-DEP force to concentrate the bacteria into the center of the microchannel, and direct them toward the sensing microchannel which has a diameter smaller than one-third of the first channel. The bulk fluid flows into the outer channel towards the waste outlets. (2) Bacteria sensing region consists of three interdigitated electrode arrays (IDEA) with varying number of fingers (30, 20 and 10 pairs respectively) coated with anti-E.coli antibody. As E.coli reaches the sensing region it binds to the antibody on IDEA surface, and results in impedance change. This has enabled detection of a very low concentration of bacteria with a very high sensitivity and rapidly. Fabrication of the biosensor was performed on a glass substrate using SU8 negative photoresist to form the microchannel, gold electroplating to form the vertical focusing electrode pair, thin gold film to form the detection electrode, the finger electrodes, traces and bonding pads, and PDMS to seal the device. Various low concentration E.coli samples were tested to determine the sensitivity of the biosensor and the lowest detection limit of the biosensor was found to be 14 CFU/ml. The total turnaround time, from antibody immobilization to pathogen detection was about 2 hours.