Release of 5-fluorouracil from thermosensitive magnetoliposomes induced by an electromagnetic field

Abstract

Thermosensitive magnetoliposomes (TMs) have been proposed by the authors as a new drug carrier for magnetic targeting (Viroonchatapan et al., Pharm. Res. 12 (1995) 1176–1183; Viroonchatapan et al., Life Sci. 58 (1996) 2251–2261). The present study was carried out to investigate the properties of selective heating and thermosensitive drug release of TMs caused by an electromagnetic field. TMs containing 5-fluorouracil (5-FU) were prepared by reverse-phase evaporation. They were selectively heated by a 500-kHz electromagnetic field in a temperature-controlling unit kept at 37°C, and the properties of single and multiple release of 5-FU from TMs were examined. The results showed that the temperature of TMs could be effectively elevated to 42°C and maintained at this temperature against a cooling effect of the temperature-controlling unit, which mimics an in vivo situation where temperature rise in the site of TM delivery would be hindered by blood flow and surrounding tissues. The release of 5-FU from TMs in response to electromagnetic field-generated heat was accomplished. Moreover, the drug release could be executed several times by multiple exposure to the field. In conclusion, this paper presents for the first time a demonstration of both single and multiple thermosensitive drug release from TMs, induced by an electromagnetic field. It is suggested that TMs would be useful in future cancer treatment by magnetic targeting combined with drug release in response to electromagnetic induced hyperthermia.