Drug release, stability and efficiency of vitamin e loaded in liposomes for bovine sperm protection in cryopreservation medium.

BACKGROUND:It is known that a considerable number of drugs in clinical use or under development are water-insoluble drugs with poor bioavailability. The liposomal delivery system has drawn attention as one of the noteworthy approaches to increase both dissolution and absorption because of its biocompatibility and ability to encapsulate hydrophobic molecules in the lipid domain. However, several drawbacks have been reported, the most common is liposome structural instability. OBJECTIVE:To encapsulate alpha tocopherol into liposomes, to determine the new formulation stability and to study the drug-release of alpha tocopherol into the sperm cryopreservation medium. MATERIALS AND METHODS:The liposomes prepared by an ethanol injection method were characterized for size stability, alpha tocopherol release and sperm motility tests. RESULTS:The prepared unilamellar vesicles had both narrow size distribution (around 99 nm) and a good physical and chemical stability at 4°C during 12 months. The liposomes did not release the vitamin E immediately, but retained the protectant for 24 hours, probably due to the rigidity of the liposomal fence which was reinforced by adding cholesterol. Then, all vitamin E molecules were released by 48 hours. Release was potentially by Fickian diffusion probably by the creation of mini-ducts due to both agitation and fence hydration. Moreover, semen motility treated with vitamin E liposome preparations was significantly improved compared to all other treatments (including commonly used sperm conservation media). CONCLUSION:The stable vitamin E liposomes formulated in this work are a promising alternative for semen cryopreservation protection.