Development of Bacteria sensor using Dielectrophoresis and Electropermeabilization

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Electropermeabilization (EP) was successfully incorporated with DEPIM in order to achieve higher sensitivity for bacteria detection. Contamination of metallic ions released from electrodes, which masks subtle conductance increase caused by the released intracellular ions, was successfully suppressed by improving the pulse waveform for EP. E. coli was quantitatively detected in 3 h at 10^2 CFU/ml, which was improved by two orders of magnitude relative to the conventional DEPIM without EP. The proposed technique is promising as a fast and sensitive bacteria inspection method and may be easily incorporated into Bio-MEMS or μ-TAS devices.In order to add selectivity to DEPIM or EPA-DEPIM inspection of bacteria, new inspection protocols were demonstrated using an electrode chip on which a target bacteria-specific antibody was immobilized in advance. In the first method, all bacteria were first trapped onto the electrode chip by strong positive DEP. In order to selectively retain the target bacteria, which could bind with the immobilized antigen, the hydrodynamic drag force was exerted by washing liquid flow. Although the number of retained target bacteria increased by using the antibody-modified chip, undesired non-specific binding to the unmodified chip also took place. The second method utilized lower DEP force so that trapping and washing processes could be simultaneously accomplished. A smaller number of retained bacteria under decreased DEP force was surely detected by EPA-DEPIM, which was more sensitive than the conventional DEPIM. It was found that this protocol could also suppress the non-specific bacteria binding and greatly improve the selectivity for the target bacteria.