Preparation Of Injectable Hybrid Hydrogels Based On Genetically Engineered Polypeptides And Their Applications In Tumor Therapy

Nowadays,cancer is one of the diseases that seriously threatens health and life of human.Traditional cancer treatments include surgery,radiation therapy,and chemotherapy.However,the treatment of tumors is still at a lower level due to high recurrence of malignant tumor and great side effects.To improve the effect of tumor therapy,many researchers have attempted to combine different methods such as chemotherapy,photothermal therapy?PTT?,photodynamic therapy?PDT?,and immunotherapy together for tumor treatment.The tumor therapy effect was enhanced on a certain extent.However,there are many challenges in the preparation of compound nanoparticles,such as the difficult chemical modification and the complex synthesis.In situ injectable hydrogels have attracted much attention in the biomedical field due to their unique characters,such as the non-invasion,easily operation,capable of encapsulating nanoparticles and chemotherapeutic drugs,and filling complex defect cavities.Specific restriction sites and interesting sequence could be introduced into the genetically engineered polypeptides flexibly because genetically engineered polypeptides were designed based on DNA recombination technique.Genetically engineered polypeptides can be expressed by the E.coli on a large scale.The injectable genetically engineered polypeptide hydrogel prepared from the genetically engineered polypeptide possess many advantages,for instance flexible structure,single component,and good biocompatibility.In this thesis,we utilized genetically engineered polypeptides for the preparation of multifunctional injectable hydrogels and evaluated their therapy effect through in vitro and in vivo experiments.The main contents and results are summarized as follows:?1?A PC₁₀A/PTX/DOX nanogel containing hydrophobic drug paclitaxel?PTX?and hydrophilic drug doxorubicin?DOX?was designed and prepared.PTX was loaded into the hydrophobic cavities of PC₁₀A nanogel through ultrasonic treatment,and the hydrophilic drug DOX was loaded by the electronic interaction.PC₁₀A/PTX/DOX nanogel emerged obvious synergistic effect on the treatment of HeLa cells with the synergy index of 0.953.The results of in vitro and in vivo therapy of tumor showed that PC₁₀A/PTX/DOX nanogel could effectively inhibit the growth of HeLa tumors.The PC₁₀A/PTX/DOX nanogel was potential to provide a new method for loading of hydrophobic and hydrophilic drugs.?2?PC₁₀A/DOX/HAuNS nanoparticles were firstly prepared by layer-by-layer adsorption of DOX and PC₁₀A onto HAuNS nanoparticles.The PC₁₀A/DOX/HAuNS nanoparticles were“dissolved”in a PC₁₀A hydrogel through the interaction of PC₁₀A polypeptide to obtain PC₁₀A/DOX/HAuNS hydrogel.Chemotherapeutic drug DOX in the PC₁₀A/DOX/HAuNS hydrogel was absorbed on the HAuNS and directly embedded in the PC₁₀A hydrogel,which contributes to sequential release of the drug.The therapeutic experiments operated in the tumor-bearing mouse showed that PC₁₀A/DOX/HAuNS hydrogel could obviously suppress the growth of HepG2 tumors.?3?An injectable multifunctional hydrogel based on engineered coiled-coil polypeptide,Ag₂S QDs,and PTX has been developed for sustained chemo-photothermal therapy.The experimental results show that the reduction of photoacoustic signal intensity and fluorescence signal intensity of Ag₂S were consistent with the degradation of hydrogel and drug release.The fluorescence imaging of Ag₂S QD in the tumor lasted for 30 days,suggesting that Ag₂S QD can monitor the degradation of PC₁₀A hydrogels for long term.Compared with single photothermal therapy and chemotherapy,the combined therapy could effectively suppress the growth of SKOV3 ovarian carcinoma tumor.In addition,real-time monitoring of the PC₁₀A/Ag₂S QD/PTX hydrogel degradation in vivo was achieved by near-infrared fluorescence imaging and photoacoustic imaging,which was benefit for the understanding of the dynamics treatment progress of the tumors.?4?A multifunctional PC₁₀A/DOX/MoS₂ hydrogel was designed and prepared for chemotherapy/photothermal therapy/photodynamic therapy of 4T1 tumor.2D MoS₂simultaneously acts as a photothermal therapeutic agent and a photodynamic therapeutic agent.The survival rate of the mice treated with PTT,PDT,and chemotherapy increased to80%.In addition,the proportion of dendritic cells in tumors and lymph nodes,and the secretion levels of immune factors IL-6 and tumor necrosis TNF-?in the blood significantly increased in the treatment group;the number of CD4+T cells and CD8+T cells also improved.All of these results indicated that 2D MoS₂ nanosheets based PTT and PDT could trigger the anti-tumor immune response.Therefore,PC₁₀A/DOX/MoS₂hydrogel was promising to be utilized in antitumor immunity therapy triggered by PTT and PDT for malignant tumor.This thesis was devoted to the preparation of injectable multifunctional hydrogels and their applications in tumor therapy.A variety of chemotherapeutic drugs and nanoparticles were integrated in PC₁₀A hydrogels,which combined chemotherapy,PTT,PDT,and immunotherapy together.The hydrogels degradation and drug release in vivo was monitored through the near infrared fluorescence imaging and photoacoustic imaging during the tumor therapy process,which was potential to provide a new prospect for exploring hydrogel-based multimodal imaging and multimodal tumor therapy.