The Preparation And Performance Study Of Tumor Microenvironment-Responsive Polymeric Drug Carriers

Cancer is one of the most serious public health problems in the world and seriously threatens the health of human.Chemotherapy is an effective strategy for clinical cancer treatment due to its high therapeutic efficiency.Unfortunately,there are still some limitations for traditional chemotherapy such as the weak selectivity,poor bioavailability and severe side-effects.In recent years,the development of drug delivery systems based on nanotechnology has provided favorable opportunity for the efficient treatment of cancers.As one of important drug delivery systems,the polymer drug delivery systems with adjustable chemical structure and function,diversification of drug monomers,robust micellar stability and excellent biocompatibility,which can effectively solve several problems during the drug delivery process,including destruction of drug activity,weak water solubility,poor pharmacokinetics and non-targeted delivery,thus improving their therapy efficiency and reducing the side effects caused by drug leakage.Herein,we innovatively designed a series of tumor microenvironment stimuli-responsive polymer nanomaterials through atom transfer radical polymerization（ATRP）to deliver several anticancer drug agents into tumor cells.More detail of our work were given as following:1.In the present work,we have synthesized a series of amphiphilic block copolymers,which were composed a hydrophobic poly（2-（diisopropylamino）ethyl methacrylate）（PDPA）chain and a hydrophilic poly（ethyleneglycol）（MPEG）chain,and the target polymer were denoted as MPD.To be specific,the hydrophobic PDA could transform to hydrophilic segment under acidic medicum,which can further produce a pH-triggered drug release.By regulating the ratio of hydrophobic DPA block and hydrophilic MPEG block,we could obtain a diblock copolymer with ultra-high drug loading amount up to 10 wt%.Due to the amphipathic structure,the linear MPD could self-assemble into micelles in aqueous solution under appropriate concentration.The anticancer drug doxorubicin（DOX）could be encapsulated into the hydrophobic core through hydrophobic interaction,thus forming drug-loaded micelles of MPD-DOX.Nuclear magnetic resonance spectroscopy（¹H NMR）,gel permeation chromatography（GPC）and the Fourier transform infrared spectrometer（FTIR）spectra were used to determine the chemical structure of the target polymers of MPD.The dynamic light scattering（DLS）analysis revealed the low particle dispersion index（PDI）and the narrow size distribution of these MPD or MPD-DOX micelles.The transmission electron microscopy（TEM）images further indicated that these micelles exhibited nearly spherical morphology.Moreover,the pH-responsive characteristics of MPD polymers facilitated the controlled release of drug,leading to reduced toxicity to normal tissues.More importantly,the drug-loaded micelles of MPD-DOX with optimized composition exhibited excellent antitumor efficacy to human breast cancer MCF-7 cell（MCF-7 cells）human cervical cancer cell（HeLa cells）,while the blank micelles showed excellent biocompatibility and low cytotoxicity.In addition,the technologies of confocal laser scanning microscope（CLSM）and flow cytometry were utilized to analyze drug distribution in cells,and the obtained results indicated that the ultra-pH-responsive polymeric micelles could be rapidly internalized in the tumor cells,leading to an enhanced therapeutic effect.2.To deliver the hydrophilic anticancer drug Irinotecan（Ir）,we have prepared one unimolecular micelles-based drug delivery systems for cancer therapy.Firstly,a reduction-responsive prodrug monomer of MABHD-Ir with disulfide bond was designed and synthesized.The results of ¹H NMR spectrum and ¹³C NMR spectrum indicated that the target prodrug monomer was successfully synthesised.Next,the drug monomer of MABHD-Ir was polymerized with a hydrophilic monomer of poly（ethylene glycol）methyl ether methacrylate（OEGMA）usingβ-cyclodextrin（β-CD）as the macroinitiator via one step ATRP reaction,resulting in one star-like copolymer of[β-CD–P（Ir-co-OEGMA）（CPIO）.The results of ¹H NMR,GPC traces and FTIR spectra provided fully evidence to confirm the successful synthesis of target polymer.Owing to the unique star structure,the star-like CPIO polymer could form unimolecular micelles in water solution and further showed excellent micellar stability due to the feature of unimolecular micelle.The subsequent DLS analysis showed a size of 49.6 nm in diameter and a narrow size distribution for CPIO unimolecular micelles.These nano-sized unimolecular micelles had the potential for deep tissue penetration and better bioavailability,thus improving efficacy for cancer treatment.The reduction-responsive property of the polymeric micelles contributed to the controlled release of drug and the reduced toxicity to healthy tissues.Afterwards,we evaluated the in vitro anti-tumor effect of the CPIO unimolecular micelles by PrestoBlue assay,the results indicated that CPIO showed a better anticancer efficacy in comparison with free Ir drug.In addition,the results of confocal laser scanning microscope and flow cytometry analyses further revealed the excellent cellular uptake efficiency of the prodrug micelles and an enhanced therapeutic efficacy on tumor cells.The in vivo hematology assay further demonstrated that CPIO prodrug showed good blood compatibility and low toxicity.This study showed that CPIO could be as a rational design for development of stimuli-responsive polymeric prodrug for delivery of irinotecan.3.To further improve the therapeutic efficacy,we constructed a kind of dual-responsive（reduction-and pH-responsive）drug delivery system,and were used for multi-drugs delivery.Firstly,we synthesized the glutathione（GSH）-responsive star polymer prodrug（denoted as CCDO）by ATRP reaction,which contain a hydrophobic camptothecin（CPT）prodrug and PDPA chain and a hydrophilic POEGMA chain.The target polymeric prodrug could form stable unimolecular micelles due to its hydrophilic structure.Then the anticancer agents of DOX was encapsulated into the hydrophobic cavity of the CCDO unimolecular micelles through a hydrophobic-hydrophobic interaction,producing a unimolecular micelle（CCDO/DOX）with dual drugs loading.The ¹H NMR and GPC results were utilized to confirm the chemical structure of CCDO.The morphology and particle size distribution were characterized by TEM and DLS technologies.The in vitro release results demonstrated the dual-responsive feature of the CCDO/DOX micelles facilitated controlled release of both DOX and CPT simultaneously.The in vitro cytotoxicity results showed that CCDO/DOX micelles showed a superior anticancer efficacy in compared to CCDO micelles.Moreover,the in vivo performance showed that these unimolecular micelles had no significant influence on blood environment,demonstrating the potential for coordinated drug delivery.The drug delivery system may address the problems of traditional polymer-based anticancer drug carriers in a synergetic manner and offers new potential routes of cancer therapy and clinical treatments.