Controlled Synthesis of Lanthanide Upconversion Nanoparticles and Their Application in Cellular Probe and Photodynamic Therapy

Author:Chen De Xin

Supervisor:sun kang tao ke


Degree Year:2018





Precise therapy relies on technological innovations of accurate diagnosis and fine treatment methods.However,it lacks an accurate and clear understanding of the relevant mechanisms the treatment of diseases,such as tissue repair and oncology treatment.Therefore,it is urgent to inspire technology innovations in minimally invasive or noninvasive probe and therapeutic techniques,especially for multimodal imaging nanomaterial and theranostic nanoplatforms.Lanthanide upconversion nanoparticles(UCNs)have excellent biocompatibility and deep tissue penetration.Furthermore,through the lanthanide doping,core/shell structure and surface chemistry design,the fluorescence and imaging technique could be combined on same nanocomposites,which is beneficial to the expansion of new technology of integrated diagnosis and treatment.Considering the needs of cellular probe tracing in tissue repair and the demand of accurate and efficient photodynamic therapy,the controlled synthesis were explored about composition,structure,shape,drug loading,and surface modification in this paper.The nanocomposites with fluorescence,CT/MR multimodal imaging and precise photodynamic therapy capability were achieved by optimizing the design and synthesis method.Based on the study of the nanoparticles,in the precise diagnosis,we for the first time observed the migration of the labeled stem cells in vivo with the clinical CT/MR multimodal imaging technique.And with the fluorescence property,the defect sites histological graphs were observed without further staining.Thus,a correlation analysis method of clinical imaging technology and"in situ"histological observation is established for the first time,which provides a new way for non-invasive and real-time tracking the behavior of cells in vivo.Furthermore,we designed UCNs-PpIX nanoplatforms with thinner silica shell to improve the production of reactive oxygen species(ROS),controllable photosensitizer payload to adjust the efficiency of ROS generation,and molecular ligand modification for cell and subcellular organelles targeting.With the well designed nanoplatforms,we found that for the first time the mitochondria targeting mode could increase the capability of killing tumor cells by 15%compare with the normally used cell membrane targeting method.The findings indicate that specific subcellular targeting strategy may explore a new research area for PDT.Since the UCNs in the study of imaging diagnosis and therapy were of same components,the results will not only lay a good foundation for the clinical diagnosis and treatment integration of important diseases,but also the research of their related mechanism.The main research contents and conclusions are indicated as below:(1)The study were first performed on the effect of synthesis conditions for the structure and shape of NaLnF4(Ln:lanthanide)nanoparticles.Through changing the precursor and surfactant and the relative ratio,UCNs of different dopants,core/shell structure or shape were obtained,which resulted adjustable fluorescence colour,optimized brightness and better CT/MR imaging property than clinical contrast agent.(2)By improved reverse microemulsion method for surface modification and loading photosensitizer,thinner silica shell were achived reducing from the traditional method of 15 nm to 3-5 nm.Thinner shell on one hand reduced the distance and improved energy transfer efficiency between nanoparticles and photosensitizer,on the other hand,it brings amino group on the UCNs surface for molecular targeted modification.(3)The optimized UCNs modified with DNA transfection reagent3000(TS3000)showed an obvious cell biocompatibility improvement than Au nanoparticles in that the half maximal inhibitory concentration(IC50)of the UCNs was about 1500μg/mL while that of Au only 500μg/mL.As a result,the stem cells were labelled in an efficient(over 200 pg/cell)and long-term(at least14 days)manner,with almost no influence on the multi-lineage differentiation,which ensures the possibility and veracity of cellular monitoring in big animal model.With this nanoprobe,clinical dual-energy CT and MR imaging were successfully applied to observe the migration of the labeled cells on a bone-defect model of rabbit for at least 14 days.More importantly,the histological graphs were directly observed without further staining,(4)Both in vitro and in vivo experiments results suggested that specific subcellular targeting of the nanoplatforms enhances the PDT efficacy more effectively than the increase of ROS production,and the mitochondria-targeting led to better capability of killing tumor cells and inhibition of tumor growth.