The Preparation Of Ph And Redox Dual-sensitive Poly(ortho Ester Disulfide Urethanes)-based Drug Carrier And Its Antitumor Evaluation

Chemotherapy is still one of the most useful approaches to treat cancers in clinical applications.Unfortunately,the therapeutic efficacy is seriously limited because most anticancer drugs have low-selectivity for tumor cells,short circulation time in the blood stream,and serious side effect in normal tissues and organs.Recently,a lot of tumor stimuli-responsive polymeric nanocarriers have been designed to improve the therapeutic efficacy in anticancer treatment because of the specific accumulation in tumor site via the enhanced permeability and retention(EPR)effect and accelerated drug release triggered by the stimuli factors,such as pH,temperature,and redox conditions.Compared with normal tissues,solid tumors display specific tumor microenvironment,and existence of pH variation between blood vessels(pH～7.4)and intracellular spaces(pH～5.0 to 6.0).It is well-known that most of pH-sensitive polymeric drug carriers can realize drug release resulted from the cleavage of acid labile linkages in the tumor tissues.Nevertheless,the drug release depending on a single acid-responsiveness is still not desirable due to the lower dosages of anticancer drugs than the level of therapeutic window caused by the insufficient intracellular drug release,which greatly restrict therapeutic efficacy in vivo.Thus,a few polymeric drug delivery systems have been developed by the combination of pH and redox stimuli simultaneously.The intracellular concentration of glutathione(GSH)at tumor site is several times higher than that in normal cells.With the synergetic effect of GSH and pH,the dual-stimuli responsive drug carriers may have great potential for efficient chemotherapy with further optimization.In this work,we have successfully synthesized the dual-stimuli-sensitive poly(ortho ester disulfide urethanes)(POEDU)and pH sensitive poly(ortho ester urethanes)(POEU)through a facile polycondensation reaction.As well-known,reduction-responsive linkers such as disulfide would be cleaved by GSH in the cytoplasm of cancer cells.Notably,ortho ester bond as acid-sensitive linkage is chosen since it has shown excellent biocompatibility and been widely applied in biomedical fields including drug/gene delivery.Its hydrolysis rate may improve 1-4 orders of magnitude compare to other acid-labile linkages in response to mildly acidic environments.Hence,We postulate that the pH and redox dual-sensitive drug carriers may obviously enhance the therapeutic efficiency of loaded cargoes through the synergistically intracellular drug release at tumor sites.The main research contents are as follows:(1)Synthesis of two copolymers(POEDU and POEU):POEDU and POEU were obtain by active esters of 1,6-hexanediol(HD)reacted with ortho ester disulfide-based diamine and ortho ester-based diamine under the mild conditions,respectively.Then,the structure and molecular weight of POEDU and POEU were examined by 1H NMR and GPC,respectively.The results showed that POEDU and POEU were successfully synthesized with number molecular weight of 1.38 and 1.29× 104,respectively.(2)Fabrication of two nanospheres:POEDU and POEU were selected for the preparation of nanospheres using an oil-in-water single emulsion technique.The light scattering intensity and particle size of nanospheres were measured using a dynamic light scattering(DLS),and the morphologies of two nanospheres were observed by scanning electronic microscopy(SEM)and transmission electron microscopy(TEM).The results indicated that the size of POEDU and POEU nanospheres were about 200 nm and the morphology is spherical-like.In addition,POEDU nanospheres with pH and redox dual-sensitivity exhibited excellent stability in physiological condition and displayed a time-dependent degradation in DTT and mildly acidic conditions.(3)Nanospheres characterization in vitro:Doxorubicin(DOX)as a model anticancer drug could be loaded into nanospheres with with high drug loading efficiency.Drug release behavior of the DOX-loaded nanospheres(POEDU-DOX and POEU-DOX)in vitro was revealed that the fastest and complete DOX release was observed for POEDU-DOX at pH 5.0 in the presence of 20 mM DTT.In two tumor models(2D monolayer cells,3D multicellular tumor spheroids),the DOX-loaded nanospheres could be preferentially internalized by human neuroblastom cancer cell line(SH-SY5Y)and human hepatic cancer cell line(HepG2),respectively.Importantly,POEDU-DOX nanospheres showed superior antitumor effect,which was because the dual responsive POEDU-DOX could significantly increase the intracellular drug release after a quick simultaneous response to the mild acidic and reductive intracellular environment.(4)Nanospheres characterization in vivo:In vivo anti-tumor effect and drug biodistribution were evaluated in H22 tumor-bearing mice.The drug distribution and histological analysis results demonstrated that both of POEDU-DOX and POEU-DOX showed a improved accumulation in solid tumor,prolonged blood circulation time and reduced cardiac toxicity of DOX,compared to free DOX.Notably,in vivo antitumor results indicated that the POEDU-DOX displayed the best antitumor activity,resulting efficient delivery to the tumor site and sufficient drug release after cellular uptake by tumor cells.In summary,the pH and redox dual-stimuli-sensitive POEDU nanospheres have great potentials as drug carriers in cancer therapy.