Three generations of pyrenyl bis-MPA dendrimers with two different end-groups, acetonide (pyrG) or alcohol (pyr(Gn center dot OH)) (n = 1-3), were synthesized, and the pyrenyl group of the dendritic molecules was encapsulated in the arene ruthenium metallacages, Ru-6(p-cymene)(6)(OO boolean AND OO)(3)(tpt)(2) (OO boolean AND OO = 5,8-dioxydo-1,4-naphtaquinonato (donq) 1 and 6,11-dioxydo-5,12-naphtacenedionato (dotq) 2; tpt = 2,4,6-tri(pyridin-4-yl)-1,3,5-triazine). The host guest properties of guest subset of 1 and guest subset of 2 were studied in solution by NMR and UV-vis spectroscopic methods, thus allowing the determination of the affinity constants. Moreover, the cytotoxicity of these water-soluble host guest systems and the pyrenyl-dendrimers was evaluated on human ovarian cancer cells.