Dielectrophoresis and antibody mediated selective capture of microorganisms in micro-fluidic biochips

A dielectrophoretic (DEP) filter device was fabricated for antibody mediated specific capture of microorganisms. The device consisting of a network of fluidic inlet/outlet ports and chamber etched into silicon substrate with bonded glass on the top and interdigitated electrodes at the bottom of the chamber. The whole electrode array was covered with a thin silicon oxide layer for preventing electroosmotic currents at the electrodes. For selective capture of Listeria monocytogenes from the mixture of L. monocytogenes and Escherichia coli, the channel surface of the DEP filter device was functionalized with biotinylated BSA-streptavidin-biotinylated monoclonal antibody sandwich structure. Positive DEP (at 20V_pp and 1 MHz) was used to attract, capture and concentrate all bacteria in the sample from the fluid flow. About 8% Listeria bacteria were captured while no E. coli was captured with 40 min DEP. We demonstrated that this novel method combining dielectrophoresis, micro-fluidics, and antibody-antigen recognition can be used to selectively capture L. monocytogenes or other target bacteria in the micro-fluidic device with good efficiency and selectivity.