The Comparison Of In Vitro And Vivo Properties Between Paclitaxel Saturated And Unsaturated Fatty Acid Ester Liposomes

Fatty acids which can be uptaken by cells as bioprecursor or energy has a relatively complete pathway of absorption and metabolism,so it is widely used in the design of prodrugs.Recently,there have been large amounts of reports on antitumor prodrugs which were mostly modified with?-3 polyunsaturated fatty acids,such as DHA,?-Linolenic acid,conjugated linoleic acid,etc,but relatively few studies on prodrugs modified with long-chain saturated fatty acid.In this study,we choosed paclitaxel?PTX?,which was a frequently used clinical anti-tumor drug,as a model drug,and selected long-chain saturated fatty acids:palmitate acid?PA?and stearate acid?SA?and?-3 polyunsaturated fatty acids:linolenate acid?LNA?and docosahexaenoic acid?DHA?as ligends to synthesize four paclitaxel fatty acid derivatives.On this basis,the in vitro and vivo properties were studied to compare the differences of antitumor effect between saturated and unsaturated fatty acid prodrugs and to screen out a prodrug with low toxicity and high antitumor efficiency.Firstly,PTX-PA,PTX-SA,PTX-LNA and PTX-DHA were synthesized by esterification of PTX with fatty acids and confirmed by ESI-MS and ¹H NMR.The oil-water partition coefficients of the PTX derivatives determined by shake-flask method showed that the lipid solubility of four derivatives had improved in different degrees.Then,the thin-film dispersion method was used to prepare the PTX-derivative liposomes.Physical appearance,particle size and encapsulation efficiency were taken as factors to screen a better prescription and preparation process.In the end,the formulation and preparation process were determined as follows:the ration of phospholipid and drug was 25:1?w/w?,the ration of phospholipid and cholesterol was 25:1?w/w?,the content of DSPE-PEG₂₀₀₀ was 0.4%,the thin film was prepared at 45?and 90s was used to conduct miniprobe sonography.It was verified that PTX-PA,PTX-SA was more advantageous in druggability.The vitro assays proved that all the four PTX-derivative liposomes can slowly release active pharmaceutical ingredient PTX in rat plasma.After 30h,degradation ratio of PTX-PA-L,PTX-SA-L,PTX-LNA-L and PTX-DHA-L was 3.49%,6.74%,8.55%and10.26%respectively.CCK-8 assey was used to examine the cytotoxicity of PTX-injection,PTX-PA-L,PTX-SA-L,PTX-LNA-L and PTX-DHA-L.The result indicated that PTX-PA-L and PTX-SA-L,which had slower rate of drug conversion,showed slightly less cytotoxicity.The in vivo pharmacokinetic and tissue distribution studies were conducted to evaluate the release,metabolism and distribution characteristics of PTX-injection,PTX-PA-L,PTX-SA-L,PTX-LNA-L and PTX-DHA-L.The results showed that PTX-PA and PTX-SA with relatively small plasma clearance?Cl?could slowly metabolize PTX and significantly improve the AUC,T_1/2 and MRT of PTX.Eventually,the AUC and T_1/2 of PTX converted from paclitaxel saturated fatty acid ester liposomes was twice and five times more than that of PTX-injection.PTX converted from PTX-LNA and PTX-DHA with faster Cl and slower T_1/2 don't have advantages over PTX-injection.Tissue distribution studies showed that AUC_Tumor?56.08?g/g*h?of PTX converted from PTX-PA-L was significantly higher than that of PTX converted from PTX-LNA-L?28.82?g/g*h?,which proved that PTX-PA-L can be more transformed into PTX,increasing its accumulation in tumor.Finally,the anti-tumor effects and bone marrow suppression of PTX-Injection,PTX-PA-L and PTX-LNA-L were investigated on S180 tumor-bearing mice model.The results showed that the anti-tumor effect of PTX-PA-L?paclitaxel saturated fatty acid ester?was about 1.23 times better than that of PTX-LNA-L?paclitaxel unsaturated fatty acid ester?under equimolar administration,indicating that PTX-PA-L can more significantly enhance the anti-tumor activity in vivo.Blood routine examination results showed that PTX-PA-L,compared with the other two groups,had higher hemocyte levels,that is,less cytotoxic PTX-PA-L also has less bone marrow suppression toxicity.