non-uniform alternating electric field
V.M. Generalov, M.V. Kruchinina, A.G. Durumanov, S.A. Kurilovich, A.А. Gromov, A.S. Kozlov, S.B. Malyshkin
The review article presents materials reflecting the current state of dielectrophoresis method as well as the prospects of its application in biology, medicine, virology, microbiology, biotechnology, nanotechnology, etc. The method is based on the phenomenon of polarization of electric charges within the volume of biological particles (cells, bacteria, viruses, etc.) under the influence of external nonuniform alternating electric field (NAEF). The main interrelations in the theory of dielectrophoresis determining the magnitude of force affecting a biological particle in NAEF as well as the polarizability within a wide frequency range are described. The main effects of the cell behavior in NAEF are listed. The relations between the cell structure, function and polarizability are justified logically on the basis of literature data.
It has been found out that bacteria, fungi, viruses, DNA and any other biological particles become polarized in electric field. Intact cells are characterized by a high polarization degree, which changes considerably in response to the effects of various external factors including ionic force, ph, ambient temperature and the presence of toxins and viruses in the environment. These factors have a considerable impact on the cell metabolism, shape, size, chemical composition and ultimately its polarizability level. Dielectrophoresis method was used to study different changes in the characteristics of cells in response to the effects of external factors, for example, viruses, antibiotics, ionizing radiation, chemical components and ionic force of an electrolyte. The polarizability level reflects the degree of biological activity of the cell i.e. its ability to perform its function. Polarizability of a destructed cell loses any sense.
This method is most successfully used in medicine for noninvasive diagnostics of liver fibrosis based on the analysis of erythrocyte characteristics. A functional scheme of an automated plant for investigation of the properties of biological particles with dielectrophoresis method for medical purposes is presented. It is used to determine the following main parameters of erythrocytes: deformation amplitude [m]; αc is polarizability [m3]; с is the cell hardness [N/m]; ηc is the cell viscosity [Pas*s]; d is the cell dipole moment [C*m]; q is induced charge [C]; Cm is the membrane capacity. The above parameters of erythrocytes allow us to elucidate pathogenetic mechanisms at liver pathology and to place accents in therapy.