Double targeting of tumours with pyrenyl-modified dendrimers encapsulated in an arene-ruthenium metalla-prism

The self-assembly of 2,4,6-tris(pyridin-4-yl)-1,3,5-triazine (tpt) triangular panels with p-cymene ruthenium building blocks and 5,8-dioxido-1,4-naphthoquinonato (donq) bridges, in the presence of pyrenyl-containing dendrimers of different generations (P-0, P-1 and P-2), affords the triangular prismatic host guest compounds P-n subset of Ru-6(p-cymene)(6)(tpt)(2)(donq)(3) (P-n subset of 1). The host-guest nature of these systems, with the pyrenyl moiety being encapsulated in the hydrophobic cavity of the cage and the dendritic functional group pointing outwards, was confirmed by NMR spectroscopy (H-1, 2D and DOSY). The host-guest properties of these systems were studied in solution by NMR and UV/Vis spectroscopic methods, allowing the determination of their affinity constants (K-a). Moreover, the ability of these water-soluble host-guest systems to carry the pyrenyl-containing dendrimers into cancer cells was evaluated on human ovarian cancer cells. The host-guest systems are all more cytotoxic than the empty cage [1]CF3SO3 (IC50 approximate to 4 mu M), with the most active compound, [P-0 subset of 1]CF3SO3, being an order of magnitude more cytotoxic.