Research Polymyxin E Sulfate Liposomes More

The objective of this study is to develop a good and stable Polymymix E Sulfate liposomes. Polymyxin E(also known as colistin) is an antibiotic produced by Bacillus polymyxa subsp. colistinus and its sulfate salt is widely used.Polymymix E Sulfate has antibacterial activity against Gram-negative organisms which can neutralize the endotoxin which is produced by Gram-negative bacteria and it is difficult to have drug resistance. But colistin has nephrotoxicity, hepatotoxicity, neurotoxicity and strong local-stimulus,which limit the use of its injection. In order to reduce its adverse reaction,the researcher considered to prepare Polymymix E Sulfate liposomes with high EE% and little leakage by various kinds of preparative methods.Considering its properties and requests for therapy, liposome dispersion was prepared using film-dispersion and reverse phase evaporation(REV) with freezing-thawing. Single factor test had been done and the orthogonal design was adopted to obtain the optimized prescription. REV was the last choice, the better prescription was that concentration of Polymymix E Sulfate was 6mg/ml, content of Phospholipid was 60mg/ml, the ratio of Phospholipid and cholest was 6:1, the ratio of oil phase and aqueous phase was 3:1 and the EE% could exceed 45 % after three freezing thaw.Dialysis filtration was adopted to separate free drug from Polymymix E Sulfate liposomes . The concentration of Polymymix E Sulfate in liposomes was determined. The EE% was calculated. The result was verified by ultrafiltration.To resolve the instability problem of liposome dispersion, freeze-drying (lyophilization) technique was utilized to prepare freeze-dried proliposome. Its main advantage is high stability because of solid form during preservation. It can readily and quickly be reconstituted by adding water and simple shaking before use. Inspect physico-chemical properties of liposomes before and after freeze-drying,including distribution of particle diameter, EE%,pH and so on,it was seen that freeze-drying products can keep original characters and raise the stability of liposomes.However, freeze-drying process can induce serious and irreversible damage to liposomes, including size increasing, membrane rupture, liposome infusion, membrane infolding, and the drug leakage etc. So it’s of great importance to investigate each freeze-drying process and cryoprotectant formulation which can preserve the vesicles stable in freeze-drying. Screening from various cryoprotectants, sucrose and mannitol were ensured to protect Polymymix E Sulfate liposomes during freeze-drying, the ratio of Phospholipid, mannitol and sucrose was 1:0.8:0.6. The toxicity comparision between Polymymix E Sulfate and its liposomes were carried out to investigate that liposome can decrease the local-irritation and toxicity of Polymymix E Sulfate injection or not. The result of test indicated that Polymymix E Sulfate liposomes cut down the toxicity and improve the toleration.