Selective detection of bacteria by a dielectrophoretic impedance measurement method using an antibody-immobilized electrode chip

This paper describes a selective detection method for specific bacteria by using a dielectrophoretic impedance measurement method in conjunction with an antigen–antibody reaction. The authors have previously demonstrated a bacteria detection technique called DEPIM (dielectrophoretic impedance measurement) and EPA-DEPIM (electropermeabilization-assisted DEPIM) using a positive dielectrophoretic force to capture bacteria in suspension onto an interdigitated electrode chip. It has also been demonstrated that a selective DEPIM detection of specific bacteria could be realized by taking advantage of agglutination phenomena, which were caused by an antigen–antibody reaction. In the present study, other combinations of the antigen–antibody reaction with DEPIM or EPA-DEPIM were demonstrated. Antibody molecules were immobilized on the electrode chip before the preliminary bacteria trapping by positive dielectrophoresis (DEP). The bacteria were attracted to the electrode gap under the action of the positive DEP force and finally brought into contact with the glass surface to be bound with the immobilized antibody. By appropriately adjusting the balance between the DEP force and the drag force caused by liquid flow, the target bacteria (Escherichia coli) could be selectively retained on the chip surface avoiding undesired non-specific binding. The retained bacteria were electrically detected by EPA-DEPIM. It was also confirmed that the proposed method realized selective detection of the target bacteria from a mixed suspension with nontarget bacteria.