Preparation And Property Of Injectable Thermosensitive Nanogel System With Anti-protein Adsorption Characteristics And Combined With Photothermal Therapy

Injectable hydrogels are a class of gels system that can undergo sol-gel phase transition in response to external stimuli to form a hydrophilic three-dimensional network.Injectable hydrogels have been widely used in drug delivery systems,wound healing dressing and tissue engineering due to their ideal biocompatibility and intelligent responsiveness.When the injectable hydrogels are used as an anti-tumor drug carrier,it can release high-dose drugs at the tumor site with a sustained release,and avoid non-specific distribution of the drugs resulting in reducing systemic toxicity.However,drug-loaded injectable hydrogels have a tendency to adsorb proteins or microorganisms on their surface in vivo,which will block the drug release from the implant site due to the proliferation of collagen fibers.In addition,it is difficult to cure cancer completely using a single chemotherapy.Hyperthermia,as a complementary therapy for cancer,not only kills cancer cells directly,but also enhances the sensitivity of cancer cells to radiotherapy or chemotherapy.Therefore,local chemotherapy combined with hyperthermia is expected to improve the therapeutic effect of tumors.Based on the above background,an injectable thermosensitive nanogel system with anti-protein adsorption abilityhas been prepared to load small molecule photothermal reagent indocyanine green(ICG)and polymeric photothermal agent polydopamine(PDA)nanoparticles and chemotherapeutic drugs doxorubicin(DOX).The synergistic effect of chemotherapy and photothermal therapy has been evaluated in vitro and in vivo.The main experiment and results of this thesis are as follows:1.Injectable zwitterionic thermosensitive nanogels based on poly(Nisopropylacrylamide-co-methacryloylethylsulfobetaine)(poly(NIPAM-co-SBMA))were prepared by precipitation polymerization,abbreviated as NG.Dynamic light scattering(DLS)and transmission electron microscopy(TEM)were used to characterize the diameter and morphology of the nanogels.The chemical structure of nanogels was confirmed by Fourier transform infrared spectroscopy(FTIR)and 1H nuclear magnetic resonance(1H NMR).The volume phase transition temperature(VPTT)of nanogels was studied by DLS and UV-Vis spectrum.The results showed that the nanogels formed by copolymerization of the two monomers had an unfirom size with the average hydrodynamic diameter of 100 nm at 25 ?,the diameter of the dry nanogels of 90 nm and the VPTT of about 35 ?.The anti-protein adsorption properties of poly(NIPAM-co-SBMA)nanogels were studied by BCA protein quantification method.The result suggested it could avoid non-specific proteins adsorption and possessed anti-fouling property.2.Indocyanine green(ICG)and poly(NIPAM-co-SBMA)nanogels were mixed to obtain I-NG dispersion.The sol-gel phase transition behavior of I-NG dispersion was studied by vial inversion test and dynamic rheometer.The results showed that the nanogel dispersion in phosphate buffer solution(PBS,p H 7.4)with nanogels of 25 wt% and ICG of 10 ?g/m L(I-NG)was a flowing sol at room temperature,and could undergo sol to gel transition at 36 ? to form a semi-solid hydrogel.The system had an absorption in near infrared(NIR)region and could improve the stability of ICG.Under NIR laser irradiation(808 nm,1.5 W/cm2),the temperature of I-NG dispersion could be increased 10 ? in 1 min,which indicated it suitable for used in photothermal therapy of tumors.The drug release behavior of I-NG dispersion containing DOX·HCl(I/D-NG)was studied by a dialysis method.The results showed that it had a sustained release behavior,and NIR laser irradiation could accelerate the drug release.Mouse embryonic fibroblast(L929)and human liver cancer(Hep G2)cells were used as model cells to study the biocompatibility of NG and the cytotoxicity of I/D-NG dispersion.The results showed that NG had good biocompatibility,and I/D-NG dispersion had the greatest killing effect on cells under the irradiation of NIR laser.In addition,I/D-NG dispersion was intratumorally injected into H22 tumor-bearing mice,and the results showed that hyperthermia combined chemotherapy significantly improved the therapeutic effect compared with single hyperthermia or chemotherapy.3.Polydopamine(PDA)nanoparticles were prepared by oxidative self-polymerization of dopamine in a basic solution.The results of DLS and TEM showed that the prepared PDA were spherical particles with a size of 130 nm.UV-Vis-NIR absorption spectrum showed PDA nanoparticles had a strong absorption in NIR region.The PDA nanoparticles were added to 25% of nanogel dispersions to obtain PDA-NG dispersion(PDA concentration was 200 ?g/m L),which underwent a sol-gel transition at 36 ? and had strong absorption in NIR region.In vitro photothermal experiments showed that the temperature could be increased about 35 ? under NIR laser irradiation for 10 min with the photothermal conversion efficiency of 38.5%.In addition,PDA nanoparticles had excellent photothermal stability and could allow for multiple photothermal treatments.The results of cell experiments and animal experiments also showed that PDA/D-NG dispersions could significantly inhibit tumor growth under NIR irradiation,and hyperthermia combined with chemotherapy had synergistic therapeutic effects on tumors.In summary,two injectable hydrogel systems with photothermotherapy combined with local chemotherapy were prepared.Both cell and animal experiments showed that hyperthermia combined with chemotherapy had better anti-cancer effect than that of single chemotherapy or hyperthermia.Compared with I-NG dispersions,PDA-NG system had better photothermal stability and could be used for repeated photothermotherapy and promoted the release of chemotherapeutic drugs to enhance the treatment effect.