FREQUENCY-DOMAIN ELECTRICAL-CONDUCTIVITY MEASUREMENTS OF THE PASSIVE ELECTRICAL-PROPERTIES OF HUMAN-LYMPHOCYTES

An extensive set of electrical conductivity measurements of human lymp hocyte suspensions has been carried out in the frequency range from 1 kHz to 100 MHz, where the surface polarization due to the Maxwell-Wagn er effect occurs. The data have been analyzed according to well-establ ished heterogeneous system theories and the passive electrical paramet ers of both the cytoplasmic and nuclear membranes have been obtained. Moreover, a further analysis to take into account the roughness of the membrane surface on the basis of a fractal model yields new estimates for the membrane conductivity and the membrane permittivity, independ ently of the surface architecture of the cell. These findings are conf irmed by measurements carried out at higher frequencies, in the range from 1 MHz to 1 GHz, on lymphocytes dispersed in both hyperosmotic and hypoosmotic media, that influence the surface complexity of the membr ane due to the microvillous protusions. The surface roughness of the c ell is described by a macroscopic parameter (the fractal dimension) wh ose variations are associated to the progressive swelling of the cell, as the osmolality of the solution is changed.