Cell Membrane Electrical And Order Properties Under Microwaves Irradiation

Abstract

The degree of packing and mobility of phospholipidic molecules within a biological membrane are crucial for the latter to accomplish its physiological functions (e.g. transport across membrane, signaling processes etc). Consequently, any physical and/or chemical factor which affects the membrane order, may affect also its function.We studied the effect of 2.45 GHz microwaves irradiation on both biological and model membranes (dimiristoyl phosphatidyl choline liposomes), monitoring the following parameters:- membrane fluidity, by fluorescence depolarization of TMA-DPH,- membrane generalized polarization, by modifications of emission spectra of Laurdan,- membrane potential, by fluorescence quenching of DiSC3(5).The irradiation was performed directly in the spectrofluorometer, with a specially designed antenna and the temperature was continuously monitored using an optical fiber thermometer. Membrane fluidity, generalized polarization and potential were measured continuously during the irradiation.In parallel experiments the same thermal evolution of the system as in the case of microwave irradiation was simulated by means of a computer controlled Peltier thermostat.The dependency of the monitored parameters on the temperature in both cases (MW irradiation and “thermal” heating) was analyzed.In the case of liposomes we observed a rising of the transition temperature by a few degrees centigrade, depending on the applied microwaves power.The results are interpreted in terms of membrane destabilization by water penetration in the lipidic bilayer above the critical temperature, which seems to be affected by the presence of the electromagnetic field. The effects are very clear in the case of model membrane, but less evident and much more complex in the case of living cells.