Properties of acyclovir-containing liposomes for potential ocular delivery

Loading efficiency and release characteristics of ac iclovir-containing liposomes were investigated in this study. It was found that positively charged liposomes gave the highest loading efficiency. The neutral liposomes showed a loading efficiency in between those of the positively charged and negatively charged liposomes. Liposomes prepared with an acyclovir concentration of 5 mg/ml demonstrated a loading efficiency greater than that with an acyclovir concentration of 1 mg/ml. Liposomes prepared by the method of drug-lipid film hydration with medium presented a higher loading efficiency than that prepared by lipid rilm hydration with drug solution. For all liposomes, the release rate was faster at pH 7.4 than at pH 8.0. For positively charged liposomes, the release rate was faster at higher molar ratios of stearylamine. However, for negatively charged liposomes, the release rate with a molar ratio of dicetylphosphate at 0.15 was greater than at 0.3. Decrease of mobility was found for positively charged liposomes after loading with acyclovir, whereas, no significant change in mobility was observed for negatively charged and neutral liposomes. (C) 1998 Elsevier Science B.V.