Chitosan-based cross-linked fluorescent polymer containing aggregation-induced emission fluorogen for cell imaging

A chitosan-based cross-linked fluorescent polymer (Ch-EP3) containing aggregation-induced emission (AIE) fluorogen was prepared through ring-opening polymerization of carboxymethyl chitosan and an AIE monomer with two ethylene oxide groups. H-1 NMR, FT-IR, and X-ray photoelectron spectra were conducted to characterize and prove its successful synthesis. The introduction of chitosan component endowed Ch-EP3 with amphiphilic property, and Ch-EP3 could assemble into nanoparticles, which were facilely dispersed in water to form fluorescent polymeric nanoparticles (FPNs). The dynamic light scattering and transmission electron microscopy results indicated the size distribution of the FPNs was 260 +/- 12 nm with spherical shape. Fluorescent spectrum of the prepared FPNs demonstrated intense green fluorescence with high fluorescence quantum yield of 35%. The Ch-EP3 FPNs further showed excellent particle stability at highly dilute solution with low critical micelle concentration of 0.063 mg mL(-1). The synthesized FPNs also indicated high photostability under UV light irradiation for a period of 60 min. The cytotoxicity evaluation proved high cell viability after incubation of the Ch-EP3 FPNs at different concentrations for a period of 8 h or 24 h, and demonstrated highly biocompatible for cell imaging. Taking advantage of the high-performance Ch-EP3 FPNs, such as, high water dispersibility, good particle stability, and excellent photostability, this work would inspire more approaches to prepare novel cross-linked biocompatible fluorescent polymers for biomedical application. (C) 2017 Elsevier Ltd. All rights reserved.