Study On Redox-responsive Bletilla Striata Self-assembly Copolymer Micelles For Delivering Anticancer Drug As Carriers

Polymeric micelles are nanoparticles formed by self-assembly of amphiphilic copolymers in aqueous solution.Its hydrophobic core can entrap small molecules of hydrophobic drugs and macromolecular biologically active substances,improving the solubility of drugs and the stability of the drug,realizing the long circulation of the drug in the body,enhance the efficacy,and reduce toxic and side effects.A variety of advantages make it one of the hot topics in drug delivery systems and the delivery of anticancer drugs.In this thesis,the amphiphilic grafted copolymers were synthesized based on the natural water-soluble plant polysaccharides and the endogenous material stearic acid.At the same time,the redox-responsive disulfide bonds were introduced to respond to the reducing conditions of tumor tissues and tumor cells,which contribute to rapid drug release of polymer-loaded micelles at the target site and improve therapeutic efficacy.In this study,a two-step synthesis method was used to construct BSP-ss-SA?redox-responsive bletilla striata graft copolymer?.The structure of the polymer was confirmed by infrared spectroscopy and nuclear magnetic resonance spectroscopy.Polymer nanomicelles were prepared by dialysis method,the degree of substitution of stearic acid was measured by quantitative ¹³C NMR spectra.The micellarization behavior of BSP-ss-SA in water was investigated by fluorescence spectroscopy method;Docetaxel?DTX?was used as a model drug.DTX/BSP-ss-SA were prepared by emulsification-solvent evaporation method.DLS was used to investigate the particle size,particle size distribution and Zeta potential of micelles.The drug loading and entrapment efficiency of DTX in micelles were determined by HPLC.The in vitro release behavior of drug-loaded micelles DTX/BSP-ss-SA under reducing and non-reducing conditions was investigated.Using HepG2 cells as a model cell,MTT method was used to evaluate the biocompatibility of BSP-ss-SA and the in vitro antitumor activity of DTX/BSP-ss-SA micelles.4T1 tumor cells were ectopically transplanted into BALB/c mice as a model to evaluate the antitumor activity of DTX/BSP-ss-SA micelles in vivoThe results of FT-IR and ¹H-NMR spectra indicate that the BSP-ss-SA was successfully constructed,the degree of substitution of stearic acid is 13.07%,critical micelle concentration is 22.34?g/m L.BSP-ss-SA can be self-assembled in aqueous solution to form micelles with uniform particle size.The average particle size is?125.3±2.7?nm,Zeta potential is?21.8±1.8?mV.Stability test results show that BSP-ss-SA is stable at 4°C within one month,but is unstable under reducing conditions.When the mass ratio of drug to carrier is 1:12,the average particle size of DTX/BSP-ss-SA is?158.2±1.7?nm,Zeta potential is?20.5±0.1?mV,drug loading is?7.72±0.18?%,encapsulation efficiency is?95.28±0.88?%.In vitro release results showed that DTX/BSP-ss-SA exhibited a sustained release effect in phosphate buffer pH 7.4,whereas DTX/BSP-ss-SA was reduced under the conditions of 10 mM DTT reduction,the DTX/BSP-ss-SA responded quickly,releasing DTX rapidly,and the cumulative release at 3h is close to 60%,about twice that of non-reducing conditions.The results of MTT assay showed that the BSP-ss-SA had good biocompatibility,and the inhibitory effect of DTX/BSP-ss-SA drug-loaded micelles on HepG2 cells was stronger than that of free DTX group,indicating that DTX/BSP-ss-SA drug-loaded micelles can promote drug absorption and intracellular release.The results of in vivo anti-tumor experiments showed that the inhibition rate of DTX/BSP-ss-SA drug-loaded micelles on in vivo 4T1 tumors was 70.53%,which was significantly higher than that of docetaxel injection group?46.56%?,significantly increased anti-tumor effect of Sitaxide in vivo.Redox-responsive bletilla striata self-assembly micelles can be used as nanocarriers for drug delivery systems.