Fluorescent PEGulated Oligourethane Nanoparticles for Long-Term Cellular Tracing.

We have introduced a new ABA-type amphiphilic block copolymer consisting of functional oligourethane hydrophobic blocks and two polyethylene glycol (PEG) hydrophilic blocks. The polymer was synthesized in a single step by step-growth polymerization between two monomers, namely tetraphenylethylene (TPE)-diol and hexamehylene di-isocyanate in the presence of a monofunctional impurity PEG-2000. The polymer exhibits facile self-assembly in water by synergistic effects of H-bonding and π-π interaction among the oligourethane core, leading to the formation of robust nanoparticles with remarkable aggregation-induced emission (AIE). These nanoparticles show very low critical aggregation concentration, stability over a large pH window, and excellent biocompatibility as revealed by an MTT assay. Cellular imaging with cancer cells showed facile cellular uptake and, more importantly, retention of AIE in cellular milieu for long times, which was successfully utilized for long-term cancer cell tracking.