Study On Copolymers Containing Poly (D, L-lactide-b-glycolide) As Targeted Drug Carriers

In the field of biomedicine,polymersomes can selectively load the hydrophilic drug Doxorubicin(DOX)and the hydrophobic drug Paclitaxel(PTX)due to its unique hydrophilic core and hydrophobic bilayer.It is especially important in drug delivery systems.As a novel kind of nano-drug carrier,polymersomes have the characteristics of biodegradability,stability,biocompatibility and modifiable multi-functionalization and so on.By changing the type of polymers and the ratio of the hydrophilic block to hydrophobic block,polymersomes having different morphology and film properties can be prepared.The modified polymersomes can be functional,therby achieving the ability of controlling release and deliverying drug targetedly.In this thesis,Pluronic F127,D,L-LA,and GA with biodegradability and biocompatibility were selected as raw materials to successfully synthesize non-targeted and folic acid-targeted polymer materials,named PDLLAGAF127-PDLLAGA and FA-F127-PDLLAGA.After preparing two kinds of nanoparticles by using the nanoprecipitation method,the particle size distribution and internal morphology of the two nanoparticles were observed by laser particle size analyzer and transmission electron microscopy.It was found that the particle size of the two nanoparticles was between 20 nm and 100 nm,and the morphology of both nanoparticles is vesicle.In vitro release behavior study demonstrated that drug-loaded polymersomes have a certain controlled release effect on drug molecules.And both PTX and DOX showed initial burst release and subsequent slow release,which might contribute to prolong the effect time of drugs and increase their bioavailability.Human ovarian cancer cell OVCAR-3 overexpressing folate receptor was selected as a cell model to explore the cell cytotoxicity of folic acid-targeted polymersomes by using MTT assay.In vitro cytotoxicity assay indicated that the two polymer materials were not toxic to cells and had good biocompatibility.Secondly,drug-loaded polymersomes had better inhibitory effects on cells than free drug molecules.Compared with non-targeted drug-loaded PDLLAGA-F127-PDLLAGA polymersomes,the targeted drug-loaded FA-F127-PDLLAGA polymersomes had better inhibitory effects on cells.And two drugs-loaded polymersomes were more effective in inhibiting cells than one drug-loaded polymersomes.Additionally,the obtained CI50 values showed that the anti-tumor effect of DOX and PTX was synergistic,which exhibited that it was feasible and reasonable to select DOX: PTX=5:1 as the drug ratio to explore the targeted therapeutic effect of targeted drug-loaded polymersomes on tumor cells.Coumarin-6 and doxorubicin were selected as the fluorescence probes to further verify the targeted therapeutic effect of FA-F127-PDLLAGA polymersomes by cell fluorescence quantitative assay.Cellular uptake study indicated that the cellular uptake of DOX-loaded polymersomes showed a time-dependent manner.With the prolongation of time,the cellular uptake of DOX-loaded polymersomes gradually increased.Secondly,the DOX uptake of FA-F127-PDLLAGA polymersomes was higher than non-targeted PDLLAGA-F127-PDLLAGA polymersomes,further highlighting the targeted therapeutic effect of targeting FA-F127-PDLLAGA polymersomes.The distribution of drug-loaded polymersomes in the cell was investigated by cell fluorescence qualitative experiments.Fluorescence microscopy images showed that the green fluorescent C-6 was mainly in the cytoplasm.Additionally,free DOX was mostly distributed in the nucleus,and there was few red fluorescence was observed in other parts of the cell.While the red fluorescent DOX in both PDLLAGA-F127-PDLLAGA and FA-F127-PDLLAGA was found to be aggregated in the nucleus,cytoplasm and other cellular components.In conclusion,it can be preliminarily believed that folic acid-targeted novel polymersomes FA-F127-PDLLAGA has potential application value as an anti-tumor targeted drug carrier.