Fe(Ⅲ)-Shikonin Supramolecular Nanomedicine For Tumor Therapy

Despite a variety of antitumor drugs have been developed over the past decades,most of them execute their therapeutic performance upon eliciting tumor cell apoptosis.Since apoptosis-depended tumor cell programmed death is always affected by the common tumor-associated mutations such as up-regulation of anti-apoptotic proteins or down-regulation of pro-apoptotic proteins,exploring novel therapeutic agents to eradicate apoptosis-resistant tumor cells via non-apoptotic cell death pathways may be a promising strategy to overcome the limitations of existing antitumor therapies and improve the long-term chemotherapeutic efficacy.In the second chapter,we utilize the metal-polyphenol coordination interaction as driving force to design and prepare Fe（III）-Shikonin supramolecular nanomedicines（FSSNs）for combined tumor therapy via ferroptosis and necroptosis.The formation of FSSNs not only overcomes the disadvantages of low bioavailability and high toxicity toward normal cells of Shikonin,but also introduces the therapeutic function of iron ion.FSSNs will disassemble and release Fe²⁺and Shikonin in response to high concentrations of glutathione（GSH）in tumor cells.The increase of Fe²⁺level presents an efficient bioactivity to induce tumor cell ferroptosis and exhibits an outstanding GSH-responsive self-enhanced longitudinal relaxation（T₁）-weighted imaging property.In the meantime,the released Shikonin will elicit tumor cell death via necroptosis.In addition,benefiting from the targeting ability of cyclo（Arg-Gly-Asp-d-Phe-Lys）（c RGD）and the stealth effect of polyethylene glycol（PEG）,NH₂-PEG-c RGD-modified FSSNs（FSRSNs）further improve the antitumor therapeutic efficacy.The results of in vitro and in vivo experiments confirm that our Fe（III）-Shikonin supramolecular nanomedicines have excellent antitumor therapeutic effect on 4T1 tumor.In the third chapter,Fe（III）-Shikonin supramolecular nanomedicines are used as nanocarriers to load ferroptosis inducer sorafenib（SRF）and hydrogen peroxide（H₂O₂）-producing enzymes glucose oxidase（GOx）for triple ferroptosis amplification.After endocytosis into tumor cells,the Fe（III）-Shikonin shell will disassemble and release Fe²⁺,inducing tumor cell death via ferroptosis.In the meantime,GOx executes catalytic activity to produce plenty of H₂O₂and provide an acid environment for stimulating hydroxyl radical（·OH）generation via the Fenton reaction.Moreover,SRF blocks the production of GSH by inhibiting the cystine/glutamate antiporter system（System Xc^-）,further lowering the enzymatic activity of glutathione peroxidase 4（GPX4）.The up-regulation of oxidative stress and down-regulation of GPX4 significantly accelerate the accumulation of lipid peroxides and enhance ferroptosis of tumor cells.Further combining with SRF induced apoptosis and Shikonin induced necroptosis,our supramolecular nanomedicines exhibit enhanced therapeutic efficacy toward 4T1 tumors.In the fourth chapter,we employ Fe（III）-Shikonin supramolecular nanomedicines as multifunctional supramolecular immunoadjuvants for tumor vaccination.The presence of Fe（III）-Shikonin immunoadjuvants can significantly prolong blood circulation time of antigens,guaranteeing their accumulation in tumor tissues.Upon phagocytosis by tumor cells,Fe（III）-Shikonin immunoadjuvants will disassemble into Fe²⁺and Shikonin in response to GSH,leading to immunogenic cell death（ICD）of tumor cells via ferroptosis and necroptosis.ICD-released autologous tumor cell lysates and pro-inflammatory cytokines not only stimulate DC maturation and antigen cross-presentation,but also promote macrophages repolarization and cytotoxic T lymphocytes infiltration,resulting in the activation of adaptive immune responses toward solid tumors.The experimental results show that our Fe（III）-Shikonin supramolecular immunoadjuvants integrate bioactivities including eradicating tumor cells,activating antitumor immune responses,modulating immunosuppressive tumor microenvironments,and biodegradation after immunotherapy.Nanovaccines prepared upon Fe（III）-Shikonin immunoadjuvants loading tumor cell fragment（TF）（TF@Fe Shik）exhibit an efficient antitumor effect to eradicate primary tumor,a strong abscopal effect to inhibit distance tumor growth,and a long-term immune memory effect against tumor metastasis and reoccurrence.