Phytosterol Instead Of Cholesterol Research On The Stability Of Liposomes

Liposome is a type of ball shape drug carrier which was formed under the interaction of hydrophilic and hydrophobic groups of phospholipids, Liposome often used as a model of cell membrane and drug delivery carrier in the pharmaceutical and biological fields because of its good biocompatibility and safety. Liposomes have nontoxicity and immunogenicity and it is prone to biological degradation in vivo,Liposomes can also improve the stability of materials by wrapping them up, and control the drug release, make the drug targeting to increase the index of treatment, reduce the dose and side effects. Anyhow, liposomes possesses the unparalleled advantages of other drug delivery systems.Take PC and cholesterol as liposome membrane materials, construct blank liposomes by the reverse evaporation method, according to the analysis results of dynamic light scattering and atomic force microscope, when the ultrasonic time is 1 min, the average particle size of Liposome is epigranular and distributes at about 200 nm,its dispersion is good with regular spherical particles. The laetrile liposome best coating conditions were : lipid ratio of 3.9:1, laetrile quality percentage 5%, buffer pH 7.2, organic facies water phase ratio of 3.3:1 according to the principle of Box- Behnken center combination experiment design, analyzing by the response surface method.The liposome envelopment rate was 45.21%, the average grain size of 196 nm under the most optimal condition. All above provided theoretical reference for further research of water-soluble oral drug delivery system and increasing the oral absorption.Based on PC and cholesterol liposome as membrane materials, and construct liposomes by combining the reverse evaporation method- freezing and thawing method, look for new methods to avoid or reduce the contaction between drug and ultrasonic processing or organic solvent during the construction of liposomes. The best preparation conditions of liposomes were obtained through the single factor experiment and the center of the Box-Behnken combination experiment design principle, and the response surface analysis: hydration size 32 ml, ultrasonic time is 2.5 min, freezing and thawing twice. Under this condition, the liposome envelopment rate was 32.04%, the average particle size is 239 nm. The liposome system could be used to provide the theoretical reference to further study on coating of water-soluble drug system.Take phytosterol instead of cholesterol in preparation of liposomes to reduce the amount of the human body cholesterol intake and the risk of suffering cardiovascular disease. Prepare liposome in phosphatidyl choline, cholesterol and phytosterol(mixed phytosterols, beta sitosterol, stigmasterol) as the membrane material respectively, then change the component content of cholesterol and phytosterol. Measure particle size and distribution of liposomes by atomic force microscopy and dynamic light scattering instrument and found the size of liposome was bigger, and the Polydispersity Index increased. The liposome envelopment rates after replacement were compared by the ultrafiltration centrifugal- HPLC method and found the drug carring effection of liposomes constructed by phytosterol and Cholesterol were better than the only Cholesterol one,when mixed phytosterol accounted for 60%, beta sitosterol,accounted for 40% and stigmasterol account for 60% of the amount of cholesterol.Liposome constructed by Sterol were kept away from light at room temperature for 30 d, make a evalutinn of liposome every 5 d, measure and compare the leakage rate, particle size with cholesterol lipsome. it was found that cholesterol liposome emulsion after 30 d there is still not obvious floc, size change slightly, leakage rate change less, the high concentration of phytosterol liposome after replacing cholesterol appears obvious stratification and precipitation around 10 d and cannot recover to a uniform and stable emulsion after shaking. In the 5th d, the envelopment rate of liposomes constructed by Beta sitosterol(40%) is still greater than cholesterol liposomes. the oxidation resistance of beta sitosterol liposome membrane is the best, the mixed phytosterols took second place, stigmasterol liposome membrane oxidation resistance is the worst. Factors that influence the stability of liposomes are rather complicated. A small amount of beta sitosterol replace cholesterol can make liposome envelopment rate increase and antioxidant ability enhance. This topic established the feasibility of liposome preparation method about replacing cholesterol with phytosterol, study the changes of structure and properties of the liposome after replacement of phytosterols, provided a theoretical reference for phytosterols application in liposomes preparation as membrane material.