Delivery of porphin to cancer cells by organometallic Rh(III) and Ir(III) metalla-cages
Résumé
Two pentamethylcyclopentadienyl (Cp*) rhodium(III) and iridium(III) metalla-prisms of the general formula [(Cp*M)6(tpt)2(dhnq)3]6+ (tpt = 2,4,6-tri-(pyridin-4-yl)-1,3,5-triazine, dhnq = 5,8-dihydroxy-1,4-naphthoquinonato; M = Rh, [1]6+; M = Ir, [2]6+) have been synthesized by mixing in methanol the neutral dinuclear complexes (Cp*M)2(dhnq)Cl2 (M = Rh, Ir), AgCF3SO3 and tpt. In a similar fashion, the addition of porphin during the formation of [1]6+ and [2]6+ leads to the carceplex systems [porphin⊂1]6+ and [porphin⊂2]6+. All complexes were isolated as their triflate salts and characterized by different analytical techniques including for the carceplex [porphin⊂1][CF3SO3]6 by a single-crystal X-ray structure analysis. The hosts were evaluated as drug delivery vectors on the HT-29 cancer cell line, and after internalization, porphin was photo-activated to generate phototoxicity. Interestingly, the IC50 values of the empty and filled metalla-cages are around 1 μM, while upon irradiation (20 J/cm2) only lower nanomolar concentrations of the [porphin⊂cage][CF3SO3]6 systems are necessary to inhibit cell growth by 50%, showing an excellent ratio between cytotoxicity and phototoxicity.