Study On The Preparation Of Paclitaxel Proliposomes And Its Pharmacokinetics By Oral Administration

Paclitaxel?PTX?is a natural alkaloid with a considerably wide therapeutic range against ovarian cancer,breast cancer,non-small cell lung cancer,stomach cancer,head and neck carcinomas,advanced forms of Kaposi's sarcoma and acute leukemia.PTX has a high affinity to the?-subunit of tubulin and results in the disruption of dynamic equilibrium between assembly and disassembly of microtubules,which blocks cells in the late G2 and M phases of the cell cycle.Despite its strong antitumor activity,the significant activity of PTX in clinical application is greatly restricted by its poor water solubility and low therapeutic index.Therefore,we proposed to use liposome to encapsulate paclitaxel and improve its solubility,and further designed the proliposome formulation on the basis of liposome.The pharmacokinetic characteristics and tissue distribution of the proliposomes in animals were studied,and the physicochemical properties of the proliposomes were evaluated.An oral preparation of paclitaxel was developed innovatively.The content of this paper are as follows:1.Preparation of paclitaxel liposome and determinationits encapsulation efficiencyPaclitaxel liposomes were prepared with ethanol injection method.Firstly,we established a method for determination of paclitaxel in paclitaxel liposomes.The liposomal paclitaxel were separated well from free paclitaxel by the Sephadex G-50 chromatography and was detected with RP-HPLC method.On the basis of single factor,the optimal formulation of paclitaxel liposome was optimized with orthogonal design.The morphology,size distribution and Zeta potential of the best formula liposomes,and their release behavior in vitro were investigated.The results show that the method can quickly detect the encapsulation efficiency of liposomal paclitaxel.The optimal prescription screening for phospholipid concentration is 4%,cholesterol and phospholipid ratio is 1:15,tocopherol content is 5 mg,the average entrapment rate is 92.28%,the average particle size is 491.5nm,the Zeta potential is-44.21 mV.Microscopically,the morphology of the liposome was clearly visible and showed tiny vesicles.The release kinetics of the drug was investigated in pH7.40 PBS solution of 1%Tween 80,the final release model complied to the Higuchi model.2.Preparation and characterization of paclitaxel proliposomesPaclitaxel proliposomes were prepared by vacuum drying method.With the encapsulation efficiency of reconstructed liposomes as the index,the response surface design was used to select the optimum prescription.The optimal amount of phospholipid is288.75 mg,the ratio of lipid to drug is 80:1,and the loading ratio is 1.25.The morphology of proliposomes after hydration was observed by microscopy and their particle size distribution and Zeta potential were measured.The average particle size is 312.6 nm,and the Zeta potential is-44.04 mV.Differential scanning calorimetry and infrared analysis of the liposomes revealed that paclitaxel was completely entrapped and amorphous in the proliposomes.3.Pharmacokinetics of paclitaxel proliposomes in ratsA method for determination of paclitaxel in biological samples was established.Pharmacokinetic characteristics in rat after oral administration of paclitaxel proliposomes?after hydration?and paclitaxel suspension?0.5%CMC-Na suspension?were compared.Rats were fed with the preparations according to their body mass(100 mg·kg^-1).After administration,at 10,25,45,60,120,180,240,360,480,600,720 and 1440 min respectively,rats blood were taken from the posterior venous plexus of orbital vein,and the concentration of plasma drug was determined with levonorgestrel as the internal standard,and the concentration-time curve was plotted accordingly.Pharmacokinetic parameters were obtained when analyzed with Kinetica 4.4 pharmacokinetic soltware according to a non-compartmental model.In vivo pharmacokinetic studies showed that the AUC_0-t in the PTX liposomal group?PTX proliposomes after hydration?was 2.72 times longer than that in the PTX suspension group?0.5%CMC-Na suspension?and the t_1/2 was prolonged by2.32 h.4.Investigation of tissue distribution of paclitaxel proliposomes in miceThe mice were Intragastric administration of PTX proliposomes?after hydrated?and PTX suspension?0.5%CMC-Na suspension?,respectively.The dosage for each mice was50 mg·kg^-1 of PTX.Mice were killed after administration at 15 min,30 min,1 h,2 h,5 h and 9 h.The heart,liver,spleen,lung,kidney tissue were dissected and the content of paclitaxel was measured.The results of drug distribution in mice showed that PTX proliposomes?after hydration administration?were higher in the liver,lung and spleen than other organs,especially concentrated in the spleen after 1 h.On the basis of preparing paclitaxel liposome with ethanol injection method,paclitaxel was preparaed into proliposomes,and the stability of liposome was improved.The resulst of the animal studies have shown the sustained-release and targeting effects of the paclitaxel proliposomes.