The anticancer drug amsacrine is loaded inside the mesopores of mercaptopropyl-functionalized mesoporous silica nanoparticles and entrapped by capping the mesopore-entrances with Ru(bpy) sub(2)(PPh sub(3))- moieties (bpy = bipyridine, PPh sub(3) = triphenylphosphine) through mercaptopropyl-Ru coordination. Exposure to visible light irradiation leads to cleavage of the Ru-S coordination bond, which releases the anticancer drug and capping moieties from the material, as determined by absorption and fluorescence measurements. Viability tests on HeLa cells confirmed the capability of the constructed drug delivery system to induce cell death upon exposure to visible light irradiation. These results prove the applicability of a harmless, visible light as the stimulus for cancer targeting, which may lead to better clinical outcomes in anticancer therapy.