Facile fabrication of cross-linked fluorescent organic nanoparticles with aggregation-induced emission characteristic via the thiol-ene click reaction and their potential for biological imaging.

Over the past several years, the biomedical applications of fluorescent organic nanoparticles (FONs) with aggregation-induced emission (AIE) feature have been extensively explored because the AIE-active FONs could effectively overcome the aggregation caused quenching (ACQ) effect of FONs based on conventional organic dyes. The development of novel methods for synthesis of AIE-active FONs plays a centre role for their biomedical applications. In this work, we reported a facile one-step thiol-ene click reaction for fabrication of AIE-active FONs through conjugation of acrylated PEG and AIE-active tetraphenylethylene (TPE) with two ene bonds using pentaerythritol tetra(3-mercaptopropionate) as the linkage. The successful synthesis of TPE containing AIE-active copolymers was evidenced by various characterization techniques. The particle size and fluorescence properties of the resultant TPE-S-PEG copolymers were evaluated by transmission electronic microscopy and fluorescence spectroscopy. Moreover, the cell viability and cell uptake behavior was also examined to evaluate their potential for biological imaging. We demonstrated that the cross-linked TPE-S-PEG show small size, high water dispersibility, low cytotoxicity and strong fluorescence for tracing. All of these advantages endow the TPE-S-PEG FONs great potential for biological imaging applications. Furthermore, this novel click reaction can take place under mild experimental conditions with high efficiency. It could be also further expanded for preparation of multifunctional AIE-active materials due to the universality of the thiol-ene click reaction and good precursor applicapability. Taken together, we have developed a novel and effective thiol-ene click reaction to fabricate the cross-linked AIE-active FONs, which display excellent physicochemical and biological properties and are promising for biomedical applications.