Effects of Dielectrophoresis on Growth, Viability and Immuno-reactivity of Listeria monocytogenes
1 Biomanufacturing Research Institute and Technology Enterprise (BRITE), and Department of Pharmaceutical Sciences, North Carolina Central University, Durham, NC 27707, USA
2 Molecular Food Microbiology Laboratory, Department of Food Science, Purdue University, West Lafayette, IN 47907, USA
3 Birck Nanotechnology Center, School of Electrical and Computer Engineering, Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907, USA
4 Now at Center for infectious diseases, Department of Medicine, New Jersey Medical school-UMDNJ, 185 S. Orange Ave, Newark, NJ 07130, USA
5 Now at Department of Electrical and Computer Engineering and Department of Bioengineering, Micro & Nanotechnology Laboratories, University of Illinois, Urbana-Champaign, Urbana, IL 61801, USA
Journal of Biological Engineering 2008, 2:6 doi:10.1186/1754-1611-2-6Published: 16 April 2008
Dielectrophoresis (DEP) has been regarded as a useful tool for manipulating biological cells prior to the detection of cells. Since DEP uses high AC electrical fields, it is important to examine whether these electrical fields in any way damage cells or affect their characteristics in subsequent analytical procedures. In this study, we investigated the effects of DEP manipulation on the characteristics of Listeria monocytogenes cells, including the immuno-reactivity to several Listeria-specific antibodies, the cell growth profile in liquid medium, and the cell viability on selective agar plates. It was found that a 1-h DEP treatment increased the cell immuno-reactivity to the commercial Listeria species-specific polyclonal antibodies (from KPL) by ~31.8% and to the C11E9 monoclonal antibodies by ~82.9%, whereas no significant changes were observed with either anti-InlB or anti-ActA antibodies. A 1-h DEP treatment did not cause any change in the growth profile of Listeria in the low conductive growth medium (LCGM); however, prolonged treatments (4 h or greater) caused significant delays in cell growth. The results of plating methods showed that a 4-h DEP treatment (5 MHz, 20 Vpp) reduced the viable cell numbers by 56.8–89.7 %. These results indicated that DEP manipulation may or may not affect the final detection signal in immuno-based detection depending on the type of antigen-antibody reaction involved. However, prolonged DEP treatment for manipulating bacterial cells could produce negative effects on the cell detection by growth-based methods. Careful selection of DEP operation conditions could avoid or minimize negative effects on subsequent cell detection performance.