Excellent Correlation between Drug Release and Portal Size in Metalla-Cage Drug-Delivery Systems

A series of large cationic hexanuclear metalla-prisms, [Ru-6(p-iPrC(6)H(4)Me)(6)(tpt)(2)(donq)(3)](6+), [Ru-6(p-iPrC(6)H(4)Me)(6)(tpt)(2)(doaq)(3)](6+) and [Ru-6(p-iPrC(6)H(4)Me)(6)(tpt)(2)(dotq)(3)](6+), composed of p-cymene-ruthenium building blocks bridged by OO boolean AND OO ligands (donq = 5,8-dioxido-1,4-naphthoquinonato; doaq = 5,8-dioxido-1,4-anthraquinonato, dotq = 6,11-dioxido-5,12-naphthacenedionato) and connected by two 2,4,6-tripyridin-4-yl-1,3,5-triazine (tpt) panels, which encapsulate the guest molecules 1-(4,6-dichloro-1,3,5-triazin-2-yl)pyrene and Pd(acac)(2), have been prepared. The host-guest properties of these water-soluble delivery systems were studied in solution by NMR and fluorescence spectroscopy, providing the stability constants (K) for these host-guest systems. Moreover, the ability of the hosts to deliver the guests into cancer cells was evaluated and the uptake mechanism studied; the rate of release of the guest molecule was found to depend on the portal size of the host.