Facile fabrication and biological imaging applications of salicylaldehyde based fluorescent organic nanoparticles with aggregation-induced emission and ESIPT feature

Abstract

A novel AIE-active fluorogen with large Stokes shift and polymerizable group was synthesized through a one-step conjugation of 4-allyloxy-2-hydroxybenzophenone using hydrazine monohydrate. The obtained 6,6′-((1E,1′E)-hydrazine-1,2-diylidenebis(phenylmethanylylidene))bis(3-(allyloxy)phe-nol) (named as HDPMA) shows AIE feature through excited-state intramolecular proton transfer (ESIPT) mechanism. To examine its potential biomedical applications, the hydrophobic HDPMA was copolymerized with a commercial available, hydrophilic and biocompatible monomer hydrophilic poly(ethylene glycol) methyl ether methacrylate (PEGMA) through reversible addition-fragmentation chain transfer (RAFT) polymerization. The successful synthesis of the HDPMA and final AIE-active poly(PEGMA-co-HDPMA) copolymers was evidenced by a series of characterization techniques. After self-assembly, the amphiphilic poly(PEGMA-co-HDPMA) copolymers could form uniform spherical micelles and showed high water dispersibility, bright yellow-green fluorescence, preeminent photostability, low critical micelle concentration. More importantly, poly(PEGMA-co-HDPMA) FONs show outstanding biocompatibility and low cytotoxicity. With these noticeable superiorities, poly(PEGMA-co-HDPMA) FONs will become promising candidates in biochemical sensing analysis, and cell imaging, even applied in more various important fields.