Polymer nanoparticles with an embedded phosphorescent osmium(ii) complex for cell imaging

Herein, we report the development of a simple and effective method for embedding a hydrophobic phosphorescent heavy-metal complex into hydrophilic nanoparticles by emulsion polymerization. An osmium(II) complex, [Os(bpy)2(L^L)]2+(PF6−)2, has been synthesized, and its structure has been confirmed by single-crystal X-ray analysis. Phosphorescent polymer nanoparticles (PNPs) with the embedded Os(II) complex have been synthesized by emulsion polymerization. Investigation of its emission properties has shown that PNPs with the embedded Os(II) complex emits red phosphorescence in water, as well as the free Os(II) complex in organic solvents. Moreover, different from the very weak cellular uptake of the Os(II) complex, a good cellular uptake of the PNPs in cytoplasm has been observed, as well as a low cytotoxicity, making them promising candidates for use as living-cell imaging agents.