Folic acid-modified iridium(III) coordination polymeric nanoparticles facilitating intracellular release of a phosphorescent residue capable of nuclear entry

Functional polymeric nanoparticles with folic acid end-capped poly(ethylene glycol) (PEG) as the shell and an iridium(III) complex coupled with poly(4-vinylpyridine) (P4VP)/[Ir(pq)2] (pq = 2-phenylquinoline) as the core have been prepared through complexation of the pyridine moiety with [Ir(pq)2]2+ followed by dialysis against water. The nanoparticles with folic acid on the surface are capable of entering HeLa cells. It is significant that, after cellular internalization, the intracellular compound histidine can trigger release of the [Ir(pq)2]+ residue into the nucleus from the nanoparticles. This provides a new pathway for triggering the release of drugs from their carriers.