Conjugated polymer nanoparticles with aggregation induced emission characteristics for intracellular Fe³⁺ sensing

In this article, a novel zwitterionic conjugated polyelectrolyte containing tetraphenylethene unit was synthesized via Pd-catalyzed Sonogashira reaction. The resulting polymer (P2), which exhibited typical aggregation-induced emission (AIE) properties, was weakly fluorescent in dilute DMSO solution and showed bright fluorescence emissions when aggregated in DMSO/water mixtures or fabricated into conjugated polymer nanoparticles (CPNs). The nanoparticles from P2 could be prepared by reprecipitation method with an average diameter around 23 nm. Notably, the cell-staining efficiencies of lipid-P2 nanoparticles could be enhanced with lipid encapsulation and these nanoparticles were endocytosed via caveolae-mediated and clathrin-mediated endocytosis pathways. Furthermore, the lipid-P2 nanoparticles with low cytotoxicity, high photostability and efficient cell staining ability could be employed for in vitro detection of Fe³⁺ ions in A549 cells.