Study On Multivesicular Liposomes Of Oleanolic Acid

Objective:Oleanolic acid(referred to as OA)belongs to pentacyclic triterpene compounds,being used to treat acute icteric hepatitis and chronic poisoning in the clinical application.At present,the related preparation of oleanolic acid in clinical use is mainly tablets,but oleanolic acid as the fat-soluble,possesses significant first pass effect of hepar and low dissolution in gastrointestinal tract,which leads to its poor bioavailability.Therefore,the objective of this study is to prepare oleanolic acid multivesicular liposomes in order to avoid the first pass effect of liver,reduce its stimulation,maintain the therapeutic drug levels in the blood for a long time,reduce the frequency of administration and therefore enhance the patient compliance.Methods:1.OA-MVLs were prepared by double emulsion process,and the formulation was optimized by central composite design.2.The morphological characteristics,encapsulation efficiency,size distribution,and in vitro release of OA-MVLs in PBS(pH7.4)were studied.3.Further,we used MTT experiment and DAPI dying method to study the OA-MVLs inhibition and apoptosis of HepG2 cells,and further detected the uptake of OA-MVLs into the cell by the laser confocal measurement.Then we measured intracellular and extracellular OA.4.At last,the pharmacokinetics in Sprague-Dawley rats injected with OA-MVLs was studied by comparison with OA solution.Results:1.OA-MVLs was neat form and their particle sizes were accorded with normal distribution with the encapsulation efficiency of 82.3±0.61%.2.In terms of the in vitro release,the results show that there's no burst effectand 80.56±1.27%of the drug was released within 120 h approximately.These data confirmed of the sustained release pattern of OA-MVLs.The results in vitro was subject to Ritger-Peppas equation.The mechanism of release of OA-MVLs may possibly be abided by Fick diffusion.3.The results show that OA-MVLs has obvious inhibitory effect on the HepG2 cells,and can cause the apoptosis of HepG2 cells.OA-MVLs distributed on the cell membrane and nucleus after being uptaken.We also measured the change of the concentration of OA inside and outside of the HepG2 cells after the treatment.As the effect of OA-MVLs on HepG2 cells increased with time going,the OA concentration inside the cells increased gradually and the extracellular concentration changed little.With the increase of concentration of OA-MVLs,OA concentration inside and outside cells also gradually increased.4.Significant prolonged drug release of OA from MVLs could be observed in OA-MVLs groups and t1/2 of OA-MVLs was extended from 4.38±4.34 h to 48.14±27.67 h,AUC(0-t)of OA was increased from 5007.51±1346.55 ng/mL·h to 24530.94±1293.42 ng/mL.MRT was extended from 6.30±3.63 h to 56.84±28.99 h.The plasma concentration of oleanolic acid maintained above quantitative limitation at 96 h after administration of OA-MVLs.