Synthesis Of Organic Fluorescent Nanomaterials For Mouse Brain Angiography

Compared with traditional cerebral angiography,organic fluorescent nanomaterials have outstanding advantages such as high resolution,high biocompatibility,high fluorescence quantum yield and high photostability,therefore they have very broad prospective applications in imaging.In this thesis,we aim at the preparation of cerebral angiography agents with excellent imaging performance.Organic fluorescent nanomaterials with emission spectra in the visible region,near-infrared I region and near-infrared II region were designed.The organic nanomaterials fluorescence in different wavelength ranges was explored,based on which a method for optimal imaging resolution of materials in the blood vessels of the brain was devised.High-resolution cerebral angiography agents were prepared by regulating the absorption and emission properties,photostability and penetration depth of the molecules,and their application in the ischemic stroke model was explored.The main contents of the paper are as follows:First,we obtained a high-resolution imaging for mouse brain blood vessels,completed the accurate 3D reconstruction of fine network structure in cerebrovascular and located the penumbra regoin of the ischemic stroke.Two high-quantum yield organic fluorescent dyes named Dye1-SQA and Dye 2-BDT were synthesized with different emission spectra.A versatile tissue transparency method was developed,and a confocal vessel atlas of the brain slice of the mouse with ultra-high imaging resolution was obtained,and 3D blood vessel fine structure was reconstructed using ImageJ.From the statistics of three-dimensional reconstruction,the marking efficiency of the blood vessels of the brain is very high.In 150 micron thick sections,more than60%of the blood vessels are 6 to 10μm in diameter,and the finest capillary diameter is 2μm.At the same time,more than 50%of the blood vessel length is above 30μm.A high-throughput,high-resolution,and high-biocompatible multi-channel imaging was obtained by perfusing organic fluorescent micro-nanoparticles into GFP mice,whose neuron was labeled with green fluorescent protein and CX3CR1^GFP/+mice,whose microglia was labeled with green fluorescent protein.Finally,the transparent method of high resolution imaging we invented achieves precise positioning of the penumbra area of the brain.This study has a significance guidance for the application of organic fluorescent materials with high quantum yield but emission spectrum in the visible region in biological tissue imaging.It is also have a great significance for pathological research and early diagnosis of vascular diseases like ischemic stroke.Second,we proposed a strategy which is based on high penetration depth,high spatial resolution and low scattering of mouse brain angiography.Long-term and real-time monitoring of cerebral vascular blood flow velocity in living mice was obtained and application in ischemic stroke/reperfusion clinical stroke model were achieved.Taking benzothiophene as the acceptor and fluorene as the donor to form organic fluorescent nanoparticles called NIEPN,which emission is near the infrared window.At the same time,the long alkyl chain acts as a side chain,effectively preventing the energy transfer-caused fluorescence queching.The introduction of Pluronic F-127increases its water dispersibility.Two-channel imaging of NIEPN and green fluorescent protein-labeled neurons of GFP mice showed that their photobleaching resistance is much greater than that of green fluorescent protein,which is a good angiography for long-term vascular imaging.After a 360 min cycle in the body,the blood flow velocity is always maintained at about585μm/s.Based on the excellent long-term stability and biocompatibility of NIEPN,we explored the extent of damage and recovery of brain neurons in the clinical stroke/reperfusion model.This study represents a breakthrough in the assessment of brain damage caused by stroke recovery,which is useful for the systematical study on the pathological changes after the occurrence of ischemic stroke,the mechanism of drug action,and the development of new treatment methods.