Preparation Of Interfacial Crosslinked Polymer Drug-loaded Micelles And Their Application For Drug Delivery

Polymeric micelles as an anticancer drug carrier has attracted great attention in recent years because they have the advantages of improving drug solubility,prolonging blood circulation time and enhancing bioavailability.However,the poor stability in vivo and uncontrolled drug release behavior limited their further applications in clinical.In this paper,a class of amphiphilic triblock copolymers,methoxy poly(ethylene glycol)-b-poly(allyl glycidyl ether)-b-poly(ε-caprolactone)(mPEG-b-PAGE-b-PCL)were synthesized by ring-opening polymerization,in which PCL was utilized as hydrophobic segments for drug encapsulation,AGE was used for interfacial crosslinking segments,and PEG was used as the hydrophilic corona to improve dispersion in aqueous solution.Two kinds of crosslinked strategy based on the light-induced click reaction and coordination interaction was used to improve the stability of the polymeric micelles.The stability,drug loading and drug release kinetics of the crosslinked micelles were studied.The performance of cell uptake,intracellular distribution and inhibition of tumor cell proliferation were also investigated.The specific contents are as follows:(1)Investigation on preparation of DOX-loaded micelles and light-induced click crosslinkingA class of amphiphilic triblock copolymers mPEG-b-PAGE-b-PCL with different hydrophilic and hydrophobic ratios were synthesized by means of ring-opening polymerization,and their molecular structure,molecular weight and molecular weight distribution were characterized by Nuclear magnetic resonance hydrogen spectrum(~1H-NMR)and Gel Permeation Chromatography(GPC).Using DOX as the model drug,DOX-loaded micelles were prepared by dialysis method.The effect of different hydrophilic/hydrophobic ratios on loading properties was compared,and the results showed that the loading capacity increased with the increase of PCL hydrophobic chain segment.Then,the micelles were crosslinked by“thio-ene”reaction with 1,4-butanedithiol unde light irradiation.The results showed that the stability of the micelles was significantly improved and the release rate of the drug in a neutral environment was obviously reduced as well.Cytotoxicity of the blank micelles and drug-loaded micelles was assessed using MTT assays.The results showed that the copolymers had good biocompatibility and the drug-loaded micelles showed good anticancer efficiency.Confocal laser microscopy revealed that the drug-loadedmicelles could effectively enter tumor cellsand release the DOX.The targeting ability and in vivo distribution of drug-loaded micelles was investigated.The results showed that the crosslinking strategy for improving the stability of the drug-loaded micelles could significantly increase the enrichment of drugs in tumor sites and have good tumor-targeting efficiency.(2)Investigation on preparation of DOX-loaed micelles and crosslinked by cisplatin coordinationOn the basis of the previous chapter,PAGE block in the copolymers was post-modified by 3-mercaptopropionic acid.The interface sites between the hydrophilic shell and hydrophobic core in the micelles was then in situ crosslinked by CDDP through the Pt-carboxyl coordination interaction.The size and zeta potential of the micelles before and after crosslinking were measured,and the stability of the crosslinked micelles was studied by the dilution and fluorescent probe method.The DOX-loaded micelles with different cross-linking degree were prepared by controlling the COOH/CDDP feed ratio.The effect of different crosslinking degree on drug loading and drug release of polymer micelles was analyzed.It was found thatthe PEAMC/DOX/CDDP showed good size distribution and the highest CDDP content when the feeding molar ratio is 1:1.In vitro drug release demonstrated that the PEAMC/DOX/CDDP have good pH response,and increased crosslinking degree can further reduce the release rate of drugs in neutral environment.Confocal laser microscopy revealed that the drug-loaded micelles could effectively enter tumor cells and release the drug.MTT tests demonstrated the dual-drug loaded micelles have better synergistic antitumor effect than single free drug or DOX-loaded micelles.