Preparation Of Redox-Responsive Dendrimer Nanogel And Its Intergrated Application In Disgnosis And Treatment Enhanced By Ultrasound

As a systemic treatment,chemotherapy is the main way of cancer treatment.For example,using the chemotherapy drug Toyocamycin（Toy）to target the endoplasmic reticulum（ER）which is an important organelle involved in protein synthesis,folding and maintenance of cell homeostasis,can amplify ER stress and kill tumor cells.Although such direct cell-killing chemotherapy can alleviate the development of tumors,it can also cause damage to normal tissues to varying degrees,induce immune escape of tumor cells and form immunosuppressive tumor microenvironment（TME）,leading to reduced therapeutic efficacy and tumor recurrence and metastasis.The immunosuppressive microenvironment is characterized by low levels of infiltrating cytotoxic T cells,high levels of immunosuppressive cells,such as regulatory T cells and tumor-associated macrophages（TAMs）,and rich extracellular matrix.Therefore,multi-pronger regulation of the immunosuppressive tumor microenvironment during chemotherapy will effectively enhance the efficacy of chemotherapy and activate the long-term anti-tumor recurrence and metastasis ability.The key technology is to construct a nano-carrier platform to load chemotherapy drugs and TME regulatory therapeutic agents for efficient delivery and enrichment in the tumor site.It was reported that gold nanoparticles（Au NPs）can not only be used for CT imaging,but also promote the transformation of M2-type TAMs to antitumor M1-types.T cells was able to effectively activated through immune checkpoint blocking mediated by PD-L1 antibody.Ultrasound Targeted Microbubble Destruction（UTMD）can transiently break the dense matrix of tumor tissues through cavitation effect,promoting the effective enrichment of nanomaterials at the tumor sites.In addition,nanogels（NGs）have attracted wide attention as dual carriers because it can combine the unique physical and chemical properties of gels and polymer matrix materials.For example,polyamide-amine（PAMAM）dendrimer has become an ideal material for the construction of NGs due to its large number of amino groups on its surface and internal cavities that can encapsulate various therapeutic agents.At the same time,NGs can be endowed with the characteristics of intelligent drug release in response to TME（GSH,ROS,p H,etc.）by using appropriate cross-linking agents.Based on the above background,in this thesis,generation 3 PAMAM（G3.NH₂）was used to construct the redox-responsive NGs loaded with contrast agent Au NPs in situ and chemotherapy drug Toy to obtain Au/Toy@G3 NGs.Then the NGs were combined with UTMD and PD-L1 antibody for UTMD-enhanced and CT imaging-guided chemoimmunotherapy of pancreatic tumor（Pan02）model.Firstly,G3.NH₂ as the main material for NGs was modified with thiolization reagent（NHS-PEG-SAT）via acylation reaction and then self-crosslinked to generate redox-responsive G3 NGs induced by disulfide bonds via a reverse microemulsion method,which was then adopted as a nanoreactor to immobilize Au NPs in situ and physically encapsulate Toy to form the Au/Toy@G3 NGs.The results showed that NGs are uniform with average size of 193 nm,have excellent stability,GSH-responsive drug release profile,CT imaging effect and biocompatibility,as well as a long half-life.In vitro experiments demonstrated that Au/Toy@G3 NGs can effectively inhibit the proliferation of tumor cells,further suppress the growth of Pan02 cells with assistance of the UTMD.Au/Toy@G3 NGs can efficiently block IRE1α-XBP1 signaling pathway and enhance ER stress,inducing effective immunogenic death.At the same time,both Au@G3 NGs and Au/Toy@G3 NGs can promote macrophage phenotype transformation.In vivo experiments indicated that ahighly effective anti-tumor immune response inducded by enhanced chemoimmunotherapy can be gained by Au/Toy@G3NGs along with UTMD and Anti-PD-L1,resulting in effective tumor growth inhibition.In summary,along with enhanced tissue penetration via UTMD and the guidance of CT imaging,the constructed responsive Au/Toy@G3 NGs enabled efficient tumor treatment through integration of chemotherapy and immunotherapy which target tumor cells and immune cells,respectively.The findings of this study will provide new ideas for the developing novel and efficient cancer therapeutic nanomedicine.