Preparation and evaluation of mitoxantrone hydrochloride thermosensitive liposomes

Objective To prepare mitoxantrone-loaded long-circulated thermosensitive liposomes(M-LTL),establish the determination methods for the content and entrapment efficiency determination and study the thermosensitive characteristics in vitro and in vivo.Methods M-LTL were prepared by the thin film hydration method combined with pH gradient method.HPLC methods were established to determine the drug content.Liposomes and free drug were separated through Dextran G-50.Tumor-bearing mouse model was established by subcutaneous graft of H22 cancer cell.M-LTL heating-free group and mitoxantrone hydrochloride(MIT) injection group were taken as control groups,and the normal saline group as blank group.The tumor growth curve was obtained and the tumor inhibitory rate was calculated.Results M-LTL appeared uniform and mean particle size was 92nm.The average entrapment efficiency was 99.8%.The excipients and solvents did not interfere with the assay.A good linear relationship was found between peak area and the concentration of M-LTL in the range of 2-20.0 μg / ml(r = 0.9998).The in vitro release test of M-LTL demonstrated that the drug release amount was not more than 5% at 37℃ in 15 min,while about 60% of the total drug released at 42℃ in 5 min.The in vivo test demonstrated that the tumor inhibitory rate of M-LTL heating group had significant difference(P 0.05) compared with M-LTL heating-free group,injection(M-I) and normal saline groups,with tumor inhibitory rates at 81.5%,61.1% and 40.1%,respectively.Conclusion High entrapment efficiency could be attached when pH gradient method was used for M-LTL preparation.The method is simple,accurate and reliable for the determination of the content and entrapment efficiency.M-LTL has an obvious thermosensitive characteristic both in vitro and in vivo.