CHARACTERISTICS OF MITOXANTRONE LOADING ON LIPOSOMES

The characteristics of mitoxantrone loading on liposomes was investigated. It was found that negatively charged liposomes at the ionic strength 0.154 and pH 5.7 gave a high loading efficiency. It should be noted that the surface charges of the liposomes were subject to change from negative to positive by the influence of the interacted mitoxantrone. The neutral liposomes demonstrated a profile of loading efficiency similar to that of the negatively charged liposomes against the added mitoxantrone concentration; however, they had a lower magnitude of the loading efficiency. In the positively charged liposomes the loading efficiency increased with the added mitoxantrone concentration. At a mitoxantrone concentration of 26-mu-mol/ml, the loading efficiency was similar to that of the negatively charged liposomes. The effect of galactocerebroside on the loading efficiency increased with added mitoxantrone concentration. The liposomes with 1.0 molar ratio galactocerebroside resulted in the highest loading efficiency in high concentrations of mitoxantrone. The loading efficiency had no dependence on the phospholipid concentration used for making liposomal membrane. An almost identical value of the loading efficiency was obtained when ultracentrifuge and dialysis methods were used to separate the mitoxantrone-containing liposomes from free drugs. The effect of vortexed and sonicated liposomes on the loading efficiency gave a similar result although the particle size was different.