A biocompatible cross-linked fluorescent polymer prepared via ring-opening PEGylation of 4-arm PEG-amine, itaconic anhydride, and an AIE monomer

A novel cross-linked fluorescent polymer (PhE-ITA-PEG) was prepared through radical polymerization between an aggregation-induced emission (AIE) monomer and itaconic anhydride, and subsequent ring-opening PEGylation with 4-arm PEG-amine. The resulting fluorescent polymer could self-assemble to form polymeric nanoparticles in aqueous solution with hydrophilic PEG groups covered at the surfaces and the hydrophobic AIE components aggregated into the cores. The successful synthesis of the obtained PhE-ITA-PEG copolymer was fully characterized and confirmed by a series of techniques including gel permeation chromatography, 1H NMR spectroscopy, FT-IR spectroscopy, and X-ray photoelectron spectroscopy. Meanwhile, transmission electron microscopy and dynamic light scattering have been carried out to determine the morphology and distribution of these polymeric nanoparticles. UV-visible absorption spectra and fluorescence spectra have also been investigated to study their optical performances. Finally, biocompatibility and cell uptake behaviour of the PhE-ITA-PEG nanoparticles were further evaluated to explore their potential biomedical applications. The results demonstrated that PhE-ITA-PEG could self-assemble to form uniform spherical nanoparticles with diameters ranging from 50 to 80 nm and showed high water dispersibility, intense yellow fluorescence quantum yield (38%) and excellent biocompatibility, which made them promising candidates for cell imaging. More importantly, the strategy of facile ring-opening PEGylation of 4-arm PEG-amine, itaconic anhydride, and an AIE monomer in this work will provide a new path to prepare more novel biocompatible AIE-based cross-linked fluorescent polymers, and would expand the range of their bio-applications.