Liposome: A model for probing the interaction of Electrmagnetic Fields and biosystems.

Liposomes are very useful model membrane systems: Although they are unable to mimic all the complexity of a cell membrane, they have a well-defined chemical composition, the capacity to arrange themselves in bilayers, selectivity to ionic species and molecules, and many other useful features. Interactions can take place between this model system and electromagnetic fields (EMFs) at different frequencies, from extremely low frequency up to microwave and THz range, so that, a comparative evaluation of the observed effects with different EMF components is allowed. In this context we used cationic Carbonic Anhydrase (CA)-loaded liposomes. The CA was entrapped into these liposomes and the hydrolysis rate of substrate p-nitrophenyl acetate (p-NPA) added in the bulk aqueous phase was adopted as the index of membrane permeability changes. In fact previous kinetic experiments showed a very self-diffusion rate of p-NPA across intact liposome bilayer. Observations reported by our group evidenced that combined 7 Hz sinusoidal (Bacpeak = 50mT) and parallel static (Bdc = 50mT) magnetic fields can induce permeability changes in these liposomes. Further, we reported on the effects of 2.45 GHz microwave exposure (6 mW/g) on the permeability of these cationic liposomes. Finally, we report on the effects of 130 GHz radiation modulated at low frequency of 5, 7 and 10 Hz on the permeability of these cationic liposomes. The enzyme activity, as function of increased diffusion of p-NPA, rises from 23% to 61% over 3 min of 130 GHz radiation modulated at 7 Hz, at incident intensity of 10.5 mW/cm2, and a peak electric field of 2.6 kV/cm. The increase of the incident intensity up to 17 mW/cm2 did not further increase the enzyme activity. This biological model demonstrates an extraordinary sensibility in revealing the influence of EMFs on the lipid bilayer permeability and allowed an interaction mechanism with an ELF magnetic field to be derived.