Effect of microwave radiation on permeability of liposomes. Evidence against non-thermal leakage.

Bergqvist B, Arvidsson L, Pettersson E, Galt S, Saalman E, Hamnerius Y, Norden B,

Biochim Biophys Acta 1201(1):51-54, 1994

The effect of 2.45 GHz microwave radiation on the permeability of unilamellar phosphatidylcholine liposomes has been studied. Leakage of 5(6)-carboxyfluorescein from the liposomes was measured using spectrofluorimetry after exposure to either microwaves or thermal heating for 5-20 min intervals. The exposure temperature, 37.6 +/- 0.5 degrees C, was well above the phase transition temperature of the lipid membrane.

The microwave exposure did not result in any non-thermal increase in permeability above that produced by thermal heating. This study refutes the results reported by Saalman et al. in which an increased liposome permeability due to microwave exposure was reported.

The refined analysis in the present study shows that this increased liposome permeability was not a non-thermal microwave effect.