Evaluation of process-induced dimensional changes in the membrane structure of biological cells using impedance measurement

摘要

The impact of high intensity electric field pulses,high hydrostatic pressure,and freezing-thawing on local structural changes of the membrane was determined for potato,sugar beet tissue,and yeast suspensions.On the basis of the electrophysical model of cell systems inbiological tissues and suspensions,a method was derived for determining the extentof local damae of cell membranes.The method was characterized byan accurate and rapid on-line deermination of frequency-dependent electrical conductivity properties from which information on microscopic events on cellular level may be deduced.Evaluation was based on the measurement of the relative change in the sample's impedance at characteristically low (f_1)and high (f_n) frequencies within the #beta#-dispersion range.For plant and animal cells the characteristic frequencies were f_1approx=5 kHz and f_h>5 MHz and for yeast cells in the range f_1approx=5 kHz and f_h>25 MHz.The observed consideration of the time-dependent nature of the procesing effects and stress reactions of the biological systems,whichranged from seconds to severalhours.A very low but significantly detecta le membrane damage (0.004%% of the total area)are found after high hydrostatic rpessure treatemnt of potato tissue at 200 MPa.The membrane rupture inplant tissue cells was higher after freezing and subsequent thawing (0.9% of total area for potatocells and 0.05-0.07% for sugar beet cells determined immediately after thawing),which increased substantially during the next 2h.