Folate-and Gd³⁺-functionalized Near-infrared Fluorescent Polymer Dots For Multimodal Imaging And Photodynamic Cancer Therapy

In recent years,the incidence and mortality of cancer are growing rapidly and have caused a serious threat to human life,so achieving early diagnosis and treatment of cancer is very important for improving the quality of human life.Multi-modality imaging technology combines the advantages of a variety of imaging technologies and can obtain more comprehensive diagnostic information,which is conducive to the accurate diagnosis of the tumor.Clinical diagnosis and treatment of cancer is usually separated,this approach may delay the best treatment time,and can not track the therapeutic effect in real time.Therefore,achieving the integration of diagnosis and treatment is an inevitable trend for clinical cancer treatment,which poses a requirement for the development of nano-probes that combine multimodal imaging with therapy.Fluorescent conjugated polymer dots is a new kind of fluorescent nanoprobe developed in recent years.It has many advantages such as low toxicity,structural diversity,designable function,good biocompatibility and so on.It is widely used in fluorescence imaging,while multimodality imaging combined with other modal imaging methods based on conjugated polymer dots is rarely explored.Combining fluorescence imaging with high sensitivity and MRI with good soft tissue resolution will greatly improve the sensitivity of detection and obtain fine anatomical information.Therefore,the photosensitizer NIR775 was loaded into the conjugated polymer dots through physical coating to make it can be used for near-infrared fluorescence imaging,photoacoustic imaging and photodynamic therapeutic effect;Multi-modal imaging can be achieved by modifying Gd³⁺into the fluorescent conjugated polymer nanoprobe.By folic acid functionalization,the probe can be targeted to the tumor.Therefore,the integration of tumor diagnosis and targeted therapy is achieved.Therefore,the research of this thesis has three parts:The preparation and characterization of folate and Gd³⁺functionalized PFBT near-infrared fluorescent polymer dots;The targeting effect and photodynamic therapy effect of the polymer dots to cancer cells;In vivo multimodal imaging and photodynamic therapy of Tumor.The main results are as follows:?1?By nano-coprecipitation,NIR775,PE-FA and DTPA-BSA?Gd?doped PFBT near-infrared fluorescent polymer dots were prepared.The probe possesses the function of folate receptor targeting,and has fluorescence imaging,MRI imaging and photoacoustic imaging for triple-mode imaging.The relaxation rate r₁=16.98mM^-1·s^-1.Under light illumination,the probe can generate singlet oxygen,which can be used for photodynamic therapy of tumor.?2?The targeting effect of different polymer dots in cells was explored by confocal laser scanning microscopy and flow cytometry.The in vito photodynamic experiments were carried out by cell staining.Finally,the dark toxicity and phototoxicity of the polymer dots was evaluated by CCK-8.The results showed that the fluorescence intensity in the cells was enhanced after the folic acid functionalization,and the signals were scattered around the nucleus or concentrated in one point.After light irradiation,singlet oxygen was generated in the cells,obvious cell apoptosis and necrosis and lysosomal rupture were observed.The CCK-8 results showed that the polymer dots had weak dark toxicity and strong phototoxicity.?3?The in vivo fluorescence imaging showed that the polymer dots can target to the tumor and some signals were located in the liver;MRI results showed that the signal intensity in tumor site increased after the injection of the polymer dots,which was consistent with the fluorescence imaging results;For photoacoustic imaging,the signal was only detected in the liver;In vivo photodynamic therapy results showed that the polymer dots can inhibit tumor growth and cause death of tumor cells while no toxicity was observed to normal tissues.