Two hydrophobic pyrenyl-containing cycloplatinate complexes (2-(1-pyrenyl)pyridine)Pt(acac) (Pt-1) and {2-(4-(1-pyrenyl)phenyl)pyridine}Pt(acac) (Pt-2) (acac = acetylacetonato) have been encapsulated in the hexacationic water-soluble metalla-cage [(p-cymene)(6)Ru-6(donq)(3)(tpt)(2)](6+) (donq = 5,8-dioxydo-1,4-naphthoquinonato, tpt = 2,4,6-tri(pyridin-4-yl)-1,3,5-triazine). The host-guest systems [(Pt-1)subset of cage](6+) and [(Pt-2)subset of cage](6+) have been characterized by NMR and UV-visible spectroscopy, thus confirming the encapsulation of the platinum complexes in the hexa-ruthenium metalla-cage. In addition, the cytotoxicities of the complex-in-a-complex systems have been established using human ovarian A2780 and A2780cisR cancer cell lines. This study shows IC50 values in the lower micromolar range for both compounds and on both cancer cell lines (IC50 approximate to 1 mu M): These values being higher than the empty metalla-cage which possesses an IC50 > 3 mu M. This amplified overall cytotoxicity for the complex-in-a-complex systems suggests an efficient delivery of the hydrophobic complexes by the water-soluble arene ruthenium metalla-cage. (C) 2012 Elsevier B.V. All rights reserved.