Selective detection of specific bacteria using dielectrophoretic impedance measurement method combined with an antigen–antibody reaction

This paper describes a new selective detection method for specific bacteria by using a dielectrophoretic impedance measurement method combined with an antigen–antibody reaction. The authors have previously proposed a bacteria detection technique called dielectrophoretic impedance measurement (DEPIM) using positive dielectrophoretic force to capture bacteria in suspension onto an interdigitated microelectrode array. In this paper, the authors propose a selective bacteria detection method using DEPIM combined with an antigen–antibody reaction. A suspension containing Escherichia coli (E. coli) and Serratia marcescens (Serratia) was tested as a sample specimen. Those two bacteria were captured onto a microelectrode by positive dielectrophoresis in almost equal amounts. Agglutination of target bacteria caused by an antigen–antibody reaction was combined with conventional DEPIM in two different ways. As a result of agglutination, target bacteria became larger than nontarget ones and could experience higher dielectrophoretic force. In one method, E. coli and Serratia were trapped together under positive dielectrophoresis and then agglutinated E. coli was selectively left in the electrode gap by washing process. In the other method, agglutination products, which had been produced in advance, were selectively trapped and detected by DEPIM. It was experimentally confirmed that proposed two methods could selectively detect E. coli from the mix suspension as long as E. coli population was more than that of Serratia.