Construction Of Intelligent Star-like Polymeric Nanomedicine Delivery System For Anti-tumor Application

Cancer is one of the biggest diseases in the world due to its high morbidity and high mortality,which seriously threatens the health of human.Nanotechnology-based drug delivery systems show unique advantages during the treatment of cancer in comparison with traditional medicine.Meanwhile,high efficient and safe drug delivery system is essential to the therapeutic efficacy.In recent years,the intelligent drug delivery systems responding to tumor microenvironment and normal physiological environment have been attracted more attention from researchers.Polymeric controlled drug release systems are characterized by adjustable chemical structure,various functions,high drug loading amount and good biocompatibility,and can effectively solve the problems such as poor water solubility,low bioavailability,uncontrollable release of drug molecules and low therapeutic efficiency,and have unique advantages in nanomedicine-based tumor therapy.In this paper,we innovatively propose a new synthetic strategy to construct a kind of tumor microenvironment stimuli-responsive star-like polymers,which have the dual advantages of traditional linear polymer with high drug loading and unimolecular micelle with high micellar stability.Upon the?-cyclodextrin(?-CD),we have designed a series of intelligent star-like nanomedicine delivery systems gathering ultra-small micellar size,high drug loadings,the micellar stability and controlled release into one system,and systematically evaluate its antitumor activity in vivo and in vitro.The research contents of this thesis are mainly divided into the following three parts:1.Atom transfer radical polymerization(ATRP)reaction was used to synthesize a kind of drug delivery systems based on pH sensitive star-like block copolymer for the delivery of antitumor drug doxorubicin(DOX).This star-like copolymer showed a core-shell structure and consisted of a?-CD core and an amphiphilic poly[2-(diisopropylamino)ethylmethacrylate]-b-poly[(ethylene glycol)methyl ether methacrylate]block polymer shell(?-CD-PDPA-b-POEGMA,CPO).The results of ~1H NMR and gel permeation chromatography(GPC)suggested that the PDPA or POEGMA chain could be adjusted,showing the controllability of the synthetic process.Due to the amphiphilic structure,these CPO polymers could form unimolecular micelles in aqueous solution and organic solvent(e.g.N,N-Dimethylformamide,DMF)with different micellar sizes.The morphology and size distribution of these unimolecular micelles were determined by transmission electron microscopy(TEM)and dynamic light scattering(DLS)technologies,and the obtained results indicated that the CPO unimolecular micelles exhibited strong micellar stability.Furthermore,the hydrophobic PDPA core could be used to load hydrophobic anticancer drugs(e.g.DOX)and showed a high drug loading content.In vitro cell toxicity were determined by PrestoBlue assay and the results showed that the blank CPO micelles had excellent biocompatibility and low toxicity to cells.Furthermore,DOX-loaded CPO micelles exhibited a high antitumor activity against a wide variety of tumor cells but a lower cytotoxicity to normal cells,suggesting a selectively high toxicity to tumor cells.Additionally,the cell imaging results also revealed that the CPO as a carrier could effectively deliver drugs into tumor cells.2.In order to enhance the drug loading content,we further designed a kind of acid-active star-like polymeric prodrug of?-CD-P(DOX)-b-P(OEGMA)(DOX@CPMO)with high drug loading rate and high micellar stability.To be specific,the drug molecules of DOX were linked to the polymeric framework using a stabile hydrazine bond,which is sensitive to the acidic medium.Furthermore,the DOX@CPMO could form stable unimolecular micelles of about 35 nm in aqueous solution and organic DMF solution,which is a preferable size for the long-term blood circulation and efficient extravasation from tumoral vessels.The ~1H NMR and GPC were used to confirm the chemical structure of DOX@CPMO.In addition,by regulating the ratio of hydrophobic PDOX block and hydrophilic POEGMA block,we could obtain a diblock copolymer with ultra-high drug loading amount up to 53.1 wt%,which exhibited the pH-responsive drug controlled release behavior under the simulative tumor microenvironment.Remarkably,the in vitro experiments revealed that the drug-free CPMO unimolecular micelles showed a very weak cell toxicity to cells,indicating a good biocompatibility.Additionally,the DOX@CPMO unimolecular micelles showed higher inhibition rate against tumor cells(e.g.,human cervical cancer HeLa cell and human breast cancer MCF-7 cell)than that of normal cells(e.g.,Human umbilical vein endothelial HUVEC cell),which indicated that DOX@CPMO has a specific selectivity for targeting to tumor cells.Moreover,the fluorescence of antitumor drug DOX could be suppressed under micellar state and could be further activated under an acidic tumor microenvironment(e.g.,pH=5.0)and showed a strong fluorescence.This result further illustrated that DOX@CPMO unimolecular micelles could be served as a fluorescent nanoprobe for the fluorescence imaging mediated tumor diagnosis.Cellular imaging and cellular uptake results of DOX@CPMO unimolecular micelles provided supporting evidence to demonstrate the ideal drug distribution in cells,and could be used as an effective drug delivery system gathering diagnosis and treatment into integration.3.We further constructed a series of reduction-responsive amphiphilic star-like polymeric prodrugs which consisted of hydrophobic camptothecin(CPT)blocks and hydrophilic poly(ethylene glycol)blocks(?-CD-PCPT-POEGMA,denoted as CCP).By adjusting the ratio of hydrophobic PCPT and hydrophilic POEGMA chains,we could effectively regulate the drug loading capacity of CCP(up to 25 wt%)and hold a balance between high drug loading and good hydrophilicity.Moreover,these obtained CCP polymers could form unimolecular micelles with various sizes under different media and showed powerful micellar stability.Upon the simulated reduced tumor microenvironment,CPT drug could be rapidly released from the CCP micelles via the fracture of disulfide bond,however,this performance is strongly refrained in the physiological environment.This result suggested that CCP could effectively deliver CPT drug molecules into cells in a controlled way.The in vitro toxicity results showed that these CCP unimolecular micelles showed a higher toxicity to tumor cells(e.g.,HeLa and MCF-7 cells).The in vivo blood performance test could further indicate the good biocompatibility of CCP unimolecular micelles can reduce the side effects to normal tissues,showing a very promising potential for medical transformation.