Effects of 2.45‐GHz microwave and 100‐MHz radiofrequency radiation on liposome permeability at the phase transition temperature

Abstract

Large unilamellar dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphos-phatidylglycerol (DPPG) liposomes loaded with an aqueous chemotherapeutic drug, cytosine arabinofuranoside (ARA-C), were exposed for 30 min to 60 W/kg continuous-wave (CW) 100-MHz or 2.45-GHz radiation in vitro at temperatures between 37 °C and 43 °C. Liposomes were exposed in HEPES buffer or in HEPES buffer supplemented with 44% by volume fetal calf serum (FCS). Characteristic phase transition responses were detected in the range of 39 °C to 40 °C with the presence of FCS, increasing maximum % release of ³H-ARA-C by 20% relative to HEPES suspension. Neither frequency of electromagnetic radiation had any detectable effect on liposome permeability or the location of the phase transition in the presence or absence of FCS.