Dielectrophoresis-based micro wire biosensor for microbial detection in protein based food system

Abstract

In this study, a rapid and accurate detection method for pathogens in food systems was developed based on a functionalized micro wire sensor combined with dielectrophoresis (DEP) technique. Attenuated Escherichia coli K-12 cultures and ground beefs inoculated with the pathogens were tested in a wide range of concentration 103-108. A gold-tungsten micro wire with a diameter of 25 μm was functionalized with anti-E. coli-antibodies on the surface to capture E. coli bacterial cells from the PBS and ground beefs. To increase the possibility to be able to capture the pathogens, DEP technique consisted of the pin type of micro wire and large size of base electrode was applied under the condition of an alternating current (AC) electric field of 10 Vpp and 3 MHz. To prevent false positive signal occurred by the non-specific binding, bovine serum albumin (BSA) was used as an agent to prevent the phenomenon that various kinds of proteins in test solutions could attach the surfaces of micro wire. The resistances increased by the pathogens were measured following to the amounts of cells captured on the wire. The results demonstrated a linear relationship with the concentrations of E. coli cells of 103-107 CFU/mL and there is no significant different with PBS and ground beef after blocking. Fluorescent intensity (FI) was also proportional to concentration of E. coli cells in ranging from 103 to 107 CFU/mL, but there was no blocking effect reducing the significant difference between PBS and ground beef. Field emission scanning electron microscopy (FESEM) images were taken to visualize the circumstances of cells captured on the micro wire with and without any non-specific binding. As the developed sensor can be developed under very low prices to compare with other commercial devices, it will have a great potential for the application in food industry.