Effect of low frequency, low amplitude magnetic fields on the permeabilityof cationic liposomes entrapping carbonic anhydrase I. Evidence for charged lipid involvement

The influence of low frequency (4-16 Hz), low amplitude (25-75 mu T) magnet ic fields on the diffusion processes in enzyme-loaded unilamellar liposomes as bioreactors was studied. Cationic liposomes containing dipalmitoylphosp hatidylcholine, cholesterol, and charged lipid stearylamine (SA) at differe nt molar ratios (6:3:1 or 5:3:2) were used. Previous kinetic experiments sh owed a very low self-diffusion rate of the substrate p-nitrophenyl acetate (p-NPA) across intact Liposome bilayer. After 60 min of exposure to 7 Hz si nusoidal (50 mu T peak) and parallel static (50 mu T) magnetic fields the e nzyme activity, as a function of increased diffusion rate of p-NPA, rose fr om 17 +/- 3% to 80 +/- 9% (P < .0005, n = 15) in the 5:3:2 liposomes. This effect was dependent on the SA concentration in the liposomes. Only the pre sence of combined sinusoidal (AC) and static (DC) magnetic fields affected the p-NPA diffusion rates. No enzyme leakage was observed. Such studies sug gest a plausible link between the action of extremely low frequency magneti c field on charged lipids and a change of membrane permeability. (C) 2000 W iley-Liss, Inc.