The Study Of In-situ Injectable Hydrogels For Anti-tumor Nano-formulations Delivery

There are more than four million new cancer cases and more than two million death from cancer in China eve ry year.Cancer has been one of the most serious threatening to human health and lives.Currently,surgical resection accompanied with other treatments including chemotherapy,radiotherapy,immunotherapy etc.have been the primary treatments of cancer in clinic.Among them,chemotherapy,using chemotherapeutic agent to kill cancer cells has been the most commonly used method.For traditional chemotherapy,antineoplastic drugs are delivered intravenously or orally,where drugs have a short half-life and limited accumulation in tumor site due to lack of targeting,resulting in poor anti-tumor efficiency and severe side effect.To improve the chemotherapy efficiency,various nano-formulations have been developed including polymer micelles,liposome,inorganic particles and metal particles etc.For one side,due to the EPR effect,nano-formulations have a high accumulation in tumor site.For another side,the targeting ability and delivery efficiency could be further improved by active targeting modification of nano-formulations.However,in spite of passive and active targeting of nano-formulations,the dosage systematically administrated that can reach tumor site is still limited.In the present paper,we constructed local nano-particles delivery systems for anti-tumor drugs delivery to increase accumulation in tumor site,improve thermotherapy efficiency and expand applications of nano-formulations.Firstly,blockco-polymerpoly??-caprolactone-co-1,4,8-trioxa[4.6]spiro-9-undecanone?-b-poly?ethyleneglycol?-b-poly??-caprolactone-co-1,4,8-tri-oxa[4.6]spiro-9-undecanone??PECT?was synthesized.Based on PEC T,the thermosensitivehydrogelsystemPTX/PECT^gelassembledbyPTX?paclitaxel?-loaded PEC T nanoparticles was constructed for sustained IP chemotherapy of peritoneal carcinomatosis model.Cytotoxicity assay indicated that PECT hydrogel was biocompatible with very low cytotoxicity and PTX/PEC T^gel had enhanced cytotoxicity than free PTX.In vivo toxicity study demonstrated the biocompatibility and biosafety of PECT hydrogel as an IP chemotherapy carrier.The fluorescence imaging method was employed to monitor the intraperitoneal degradation of PECT hydrogel by labeling PECT with rhodamine B.PECT hydrogel with the dose of 200?L showed about 8 days'retention time and most of the injected hydrogel was located in the intestine.The anti-tumor efficacy study was carried out in mice bearing CT26 intraperitoneal ascites fluid as colorectal peritoneal carcinomatosis model.The result showed that intraperitoneal administration of PTX/PEC T^gel could effectively suppress growth and metastasis of CT26 peritoneal carcinomatosis in vivo,compared with Taxol?group.The pharmacokinetic studies demonstrated that PTX/PEC T^gel could improve the bioavailability of PTX by being formulated in PECT hydrogel.Overall,sustained drug concentration at peritoneal levels in combination with drug in the form of nanoparticle contrib utes to the enhanced anti-tumor efficacy.Combined chemotherapy is common in clinical treatment.The efficiency of combined chemotherapy mainly depends on the right choice of dosages and correct ratio to the target.To realize controlled co-loading and delivery of PTX and cisplatinum?CDDP?,in the present paper,an amphiphilic co-polymer with carboxy groups?polycaprolactone-g-poly?methacrylic acid??-b-poly?ethylene glycol?-b-?poly--caprolactone-g-poly?methacrylic acid???PECM?was synthesized.Based on PECT and PECM,complex micelles PECT-M CM was prepared.PECT-M CM had a uniform size distribution and spherical shape.PTX could be incorporated in hydrophobic cores of PECT-M CM by assembly and CDDP could be entrapped in polymer chain by complexation.Therefore,PTX and CDDP could be successfully co-loaded in PECT-M CM.In vitro release results showed that C DDP and PTX could be sustained released from PECT-M CM under simulated physiological environment.PECT-M CM under certain concentration can transfer from sol to gel with the temperature increased to 35 ^oC.Thus,thermosensitive hydrogel system PECT-M CM^gel composed of PECT-M CM was constructed.In vitro erosion of PECT-M CM^gel exhibited a uniform erosion rate,with discrete nano-micelles release.Cytotoxicity assay indicated that PECT-M CM was biocompatible with very low cytotoxicity and PECT-M CM with of PTX and CDDP had the optimal synergetic effect under certain ratio.Therefore,the present drug delivery system has the potential to co-deliver PTX and CDDP under fixed ratio for enhanced chemotherapy efficiency.To expand the nano-formulations that can be locally delivered and applications of in-situ hydrogel,amphiphilic block polymer methoxy poly?ethylene glycol?-b-poly??-caprolactone-co-1,4,8-trioxa[4.6]spiro-9-undecanone??mPECT?was synthesized and able to form nano dispersions with high concentration.Based on mPEC T,injectable and biodegradable supramolecular hydrogel mPECT NP/?-CD^gel was constructed.With the introduction of?-cyclodextrins??-CD?into high-concentration mPECT nanoparticle dispersion??20%W/V?,supramolecular hydrogel could be prepared by a two-level physical cross-linking of the hydrophobic cores formed by self-assembly of amphiphilic polymer mPECT and the microcrystals of polypseudorotaxanes formed by?-CD and PEG blocks.The gelation behavior depended on the concentration of nanoparticles and?-CD.The viscoelasticity and shear thinning of mPECT NP/?-CD^gel was confirmed.In vitro hydrogel erosion was demonstrated to be mainly a concentration dependent dissociation process with general release of discrete mPECT nanoparticles about 50nm that could be easily taken up by cells.The in vitro release behavior can be modulated by changing the concentration of nanoparticles or?-CD.In vitro and in vivo cytotoxicity study demonstrated its biocompatibility and biosafety.Gel formation after subcutaneous injection was also confirmed and mPECT NP/?-CD^gelel showed about 2 weeks retention time.This work validates the potential application for this supramolecular hydrogel in local and sustained delivery of nanoparticles.