Preparation Of Water-soluble AIE Fluorescent Polymer And Application In Bioimaging

In the past,fluorescent organic nanoparticles(FONs)have attracted more and more attention due to their potential applications in biology and biochemistry,and they are particularly attractive for sensing,imaging and biomedical applications.Compared with traditional fluorescent inorganic nanoparticles such as carbon dots,quantum dots and fluorescent silicon dots,FONs have many advantages,such as low toxicity,good biocompatibility,high biodegradability and adjustable function.However,most organic fluorescent groups have inherent hydrophobic groups,which lead to insolubility in aqueous solutions.Therefore,in order to improve their hydrophilic properties,the design and preparation of amphiphilic FONs are of great significance in the field of bioengineering applications.Previous studies have reported the FONs can be synthesized by non-covalent bonding.The fluorescent groups in FONs synthesized by this method may leak from particles over time.Therefore,it is necessary to introduce covalent strategy into the preparation of FONs based on AIE.In this paper,two kinds of fluorescent organic nanoparticles with stable structure,excellent optical properties and good biocompatibility were synthesized by RAFT reaction and side-chain post-modification reaction.The specific work is as follows:(1)Multicomponent Reaction(MCR)has the advantages of atomic economy,excellent modularization,high efficiency and environmental protection.We producted amphiphilic AIE fluorescent polymers by one-pot intelligent combination of RAFT polymerization and Biginelli reaction,compared with fluorescent polymers prepared by two-step method.When the feed ratio of dye TPB is 33.5%,the molar fraction of TPB in the two-step PEGPTE1 copolymer is 14.2%,and the molar fraction of TPB in the PEG-PTE2 synthesized by one-pot strategy is 22.5%.This shows that the one-pot strategy is easy to introduce TPB dye into the copolymer branched chain.The characterization and measurement of the reaction products show that the polymer synthesized by one-pot method has controllable molecular weight.In aqueous solution,the AIE active PEG-PTE2 copolymer can self-assembled into fluorescent organic nanoparticles(FONs)with a spherical shape of 100-180 nm,and its maximum emission peak appears at 460 nm,with obvious AIE phenomenon.In addition,PEG-PTE2 copolymers have shown great potential for biomedical applications due to their low toxicity and excellent cell imaging behavior through cytotoxicity tests and cell imiging behavior.(2)Due to the great advantage of FONs in bioimaging,a new type of polymerizable AIE dye named TPES was synthesized by the Suzuki coupling reaction of TPEBr and 4-vinylphenylboric acid.The crystal structure analysis showed that the dye belonged to the triclinic crystal system and P-1 space group.Compared with the precursor TBP dye,the emission wavelength of TPES is obviously red-shifted and the fluorescence intensity is stronger.Subsequently,TPES monomers obtained by RAFT polymerization were incorporated into PEG-TS polymers.The molecular weight of the fluorescent polymer was about 47000,and the polydispersity index(PDI)was about 1.3.When the feed ratio of TPES increases from 16.0% to 25.0%,the molar fraction of TPES in PEG-TS polymer increases from 15.5% to 25.6%.In aqueous solution,the prepared amphiphilic PEG-TS1 and PEG-TS2 polymers tend to self-assemble into FONs with about 150 and 400 nm diameters,which indicates that different sizes of FONs can be prepared by controlling the feed ratio of dyes.The fluorescence spectra of amphiphilic fluorescent polymers synthesized by this method show the maximum emission peak at 515 nm,and have obvious AIE phenomenon.In addition,the polymer has high water dispersion,good fluorescence and excellent biocompatibility.