Click-Derived Fluorescent Nanoparticles For Biological Imaging With Aggregation Induced Emission

Due to its unique optical properties,such as high brightness,large Stokes shift,excellent photostability,aggregation-induced emission?AIE?dyes have become a new class of fluorescent probes in recent years.Unlike traditional fluorescent probes easily suffer aggregation induced quenching?ACQ?problem,AIE fluorescent materials hardly emit weak fluorescence in the dissolved-state,while can emit ultra-bright fluorescence in the aggregated-state.The discovery of AIE fluorescent materials provides a new way to solve the problem of ACQ.However,most of the organic luminescent materials?including AIE dye molecules?are hydrophobic and low biocompatibility,which limits their application in the biological field to a certain extent.The hydrophobic AIE dye molecules were encapsulated in amphiphilic polymers and self-assembled into polymer nanoparticles by non-covalent bonding method?for example,nanocoprecipitation?to improve the hydrophilicity of AIE dye molecules.Unfortunately,the AIE fluorescence molecules can easily leak out from the polymer nanoparticles,affecting the efficiency of its biological application.In addition,traditional covalent biologic coupling strategies often require heavy metal catalysts,such as copper,or require complex multi-step pretreatment,and the potential toxicity caused by heavy metal residues is harmful to subsequent biological applications.Therefore,it is of great significance to develop efficient metal-free coupling methods for the preparation of AIE fluorescent materials with good water solubility and biocompatibility.In the second part,based on alkyne AIE fluorescent molecules?PhE-OE?,AIE active PEGMA-AGE-PhE fluorescent polymer were prepared by a catalyst-free azide-alkyne click reaction.These PEGMA-AGE-PhE amphiphilic copolymers tend to self-assemble into fluorescent nanoparticles?FNPs?with high water dispersion,strong fluorescence and remarkable biocompatibility.In addition,PEGMA-AGE-PhE FNPs can be easily ingested by L929 cells to easily light up the cells.In the third part,red fluorescent copolymer Poly?PEGY-PhE?were synthesized by combining AIE fluorescence molecule NH₂-PhE-NH₂ and biological molecule PEGY with alkyne group.Poly?PEGY-PhE?copolymers show amphiphilic and could form FNPs by self-assembly.Poly?PEGY-PhE?FNPs have good water dispersion,near-infrared fluorescence,high photostability and low cytotoxicity,as well as cell imaging ability.In the fourth part,we designed and synthesized amphiphilic PEG-MA-PhE fluorescent polymers via high efficient catalyst-free thiol-yne click reaction.Due to its unique AIE properties and amphiphilicity,these PEG-MA-PhE copolymers are readily self-assembled to obtain nanoparticles with excellent water dispersion,bright fluorescence in aqueous solutions,and high biocompatibility.These nanoparticles have also been successfully applied to cell imaging.