Study On Cell Membrane Encapsulated Nanocomposites As Photodynamic Agents

Photodynamic therapy（PDT）is a new type of tumor treatment strategy that has attracted widespread attention in recent years.Compared with surgery,chemotherapy,radiotherapy and other conventional therapeutic methods,PDT has the advantages of highly efficient and noninvasive,short course of treatment,and can be performed repetitively.The main problems that restrict the development and application of PDT include:the hydrophobic properties of photosensitizers（PS）make them easy to aggregate in aqueous solution,resulting in low efficiency and insufficient production of reactive oxygen species（ROS）;it is difficult to deliver PS efficiently and selectively to tumor cells;and the transportation and regulatory process of photodynamic agents in subcellular level are not clear.To address these issues,this thesis focuses on the study of biomimetic nanoparticles that can be used as photodynamic reagents:semiconductor polymer dots（Pdots）and covalent organic framework（COFs）are selected as nanocarriers for the delivery of hydrophobic PS.Prepared nanocomposites are coated with cancer cell membrane to enhance the specific uptake by tumor cells.The subcellular process is explored via live-cell imaging,revealing a dynamic mechanism of PDT-ROS-mitophagy-cell death.These results provide new insight into application of biomimetic nanocomposites in photodynamic therapy.This thesis consists of three parts:1.Cancer cell membrane-coated Pdots/TPP NPs as PDT reagent.Pdots（PFBT）possess superior optical properties.It can be used as a matrix to absorb light,the energy can be transferred to the photosensitizer tetraphenylporphyrin（TPP）through fluorescence resonance energy transfer（FRET）,and enhance the efficiency of light conversion and ROS generation.Herein,we successfully prepared TPP doped Pdots hybrid nanoparticles（TPHNs）.The results of spectral analysis showed that Pdots had FRET effect with TPP,and effectively increased the quantum yield of singlet oxygen（¹O₂）.In addition,the results of live-cell imaging revealed that the nanocomposite caused cell death by inducing mitophagy.2.Cancer cell membrane-coated COF/RB NPs as PDT reagentCovalent organic frameworks（COFs）is a new type of porous organic materials that constructed by forming strong covalent bonds such as,B-O,C-N,C=N,and C=C-N between light elements.COFs possess unique properties,such as large surface area,ordered pore structure and good biocompatibility,so it has potential in biomedical research.In this part,Schiff-based COFs were prepared via a mild method.The characterization of COFs through FT-IR,TEM,SEM,and XRD indicated that the prepared COFs were homogeneous,well dispersed in aqueous media and crystallized.As an attempt of its biological application,nano COFs were loaded with the photosensitizer Rose Bengal（RB）,and modified by cancer cell membrane.The cytotoxicity of COF/RB@CMV,cellular uptake,intracellular ROS production upon light irradiation and its ability to kill cancer cells were investigated.The results indicated that the nanocomposite could be effectively uptake by tumor cells,and demonstrated photodynamic therapy effect at the cellular level.3.Cancer cell membrane-coated COF/Ce6/CpG as PDT/immunotherapy reagent.In this part,we designed and prepared a kind of functional nanoparticles,trying to combine photodynamic therapy（PDT）and tumor immunotherapy（immunotherapy）.The imide-based COFs were synthesized,and the photosensitizer chlorin e6（Ce6）was loaded on the COF NPs throughπ-πstacking.The COF/Ce6 was modified by self-assembled chitosan（CS）,and then the immunostimulatory CpG oligonucleotides were combined via electrostatic interaction.The nanocomposites of COF/Ce6/CpG were then coated by cancer cell membrane.Experiment at cellular level proved that the nanocomposites could not only be effectively uptake by tumor cells to achieve photodynamic therapy effect,but also show ideal immunostimulatory effect,showing the potential in synergistic photodynamic and immunotherapy.