Preparation Of Manganese Porphyrin Carbon Dot Nano-Therapeutic Agent And For Tumor Synergistic Therapy Guided By FI/MRI Dual-Mode Imaging

Reactive oxygen species（ROS）-mediated cancer synergistic therapies such as photodynamic therapy（PDT）and chemodynamic therapy（CDT）,which can effectively kill cancer cells,have received great attention in recent years.Nanomaterials have become key materials for improving ROS-mediated cancer synergistic therapies because of their unique surface structure and good drug loading ability,which provide a powerful way for precise diagnosis and treatment of cancer.Carbon dots（CDs）,as a kind of novel nanomaterial,can not only improve the drug loading capacity but also achieve drug release from specific tumor sites due to their good water solubility and biocompatibility as well as easy preparation and modification,thus improving the therapeutic effect.Therefore,we combined the protein drug BSA-Cys-DOX with CDs to prepare novel nanotherapeutic agent Mn@CDs-BCD with p H/GSH dual response and fluorescence/nuclear magnetic dual-mode imaging for tumor chemodynamic/photodynamic/chemotherapy synergistic treatment of tumors.In this thesis,novel manganese-doped carbon dots（Mn@CDs）were prepared by a one-step hydrothermal method using the photosensitizer porphyrin as the carbon source.The protein drug BSA-Cys-DOX was synthesized by using bovine serum albumin（BSA）as a carrier,and the glutathione（GSH）-responsive small molecule cysteine（Cys）and the chemotherapeutic drug adriamycin（DOX）were connected by chemical bonding.Finally,Mn@CDs and BSA-Cys-DOX were assembled into multifunctional nanotherapeutic agent Mn@CDs-BCD by electrostatic interaction.Transmission electron microscopy（TEM）results showed that the particle sizes of Mn@CDs and Mn@CDs-BCD were 5.0±0.7 nm and 100.0±12.6 nm,respectively,and they had good dispersion.The successful coupling of DOX and the drug loading rate（52.3±3.6%）were confirmed by Fourier transform infrared（FT-IR）spectroscopy and ultraviolet-visible（UV-Vis）spectroscopy.The fluorescence spectrum of Mn@CDs-BCD exhibits strong red fluorescence emission at 645nm under excitation at 510 nm.In addition,the prepared Mn@CDs-BCD displayed excellent longitudinal relaxation rate(r₁=4.07 m M^-1s^-1)due to the doping of paramagnetic Mn²⁺,which provided the possibility of magnetic resonance imaging of tumor sites.The tumor microenvironment（TME）response properties of Mn@CDs-BCD were explored by in vitro experiments.The results of drug release experiments indicated that the drug release rate reached 81.6%after 24 h under p H=5.5 and 10 m M GSH conditions.Dissolved oxygen experiments revealed that Mn@CDs-BCD could effectively increase the level of oxygen content in solution(9 mg m L^-1)under 5%H₂O₂conditions.And Mn@CDs-BCD could decompose H₂O₂to generate·OH and O₂through Fenton-like reaction.Moreover,Mn@CDs-BCD could effectively generate ¹O₂under light conditionthus achieving synergistic treatment through multiple ROS-generating pathways to enhance the therapeutic effects of tumors.The cellular uptake,cytotoxicity and killing effect on tumor cells of the nanotherapeutic agent Mn@CDs-BCD were investigated by cellular assays.After co-incubation with 4T1 cells for 4h,bright red fluorescence could be observed in the cells,indicating that this agent could be effectively taken up by the cells.Cytotoxicity experiments demonstrated that the experimental group of Mn@CDs-BCD had no obvious cytotoxicity to normal L929 cells under no-light conditions,and the cell survival rate was above 93%.However,under light conditions,the cell survival rate was only 36%,suggesting it could effectively kill 4T1 cancer cells.In addition,intracellular ROS levels were investigated using the DCFH-DA probe,and an intense green fluorescence was observed in 4T1 cells incubated with Mn@CDs-BCD under 635 nm light conditions,indicating that Mn@CDs-BCD could effectively produce ROS to kill tumor cells.In summary,the nanotherapeutic agent Mn@CDs-BCD had good synergistic chemokinetic/photodynamic/chemotherapeutic effects and the potential of fluorescence and MR imaging,which provided an idea for researching new nanotherapeutic agents and realizing the integration of tumor treatment.