Release of copper complexes from a nanostructured sol-gel titania for cancer treatment

Copper complexes containing inorganic ligands were loaded on a functionalized titania (F-TiO2) to obtain drug delivery systems. The as-received copper complexes and those released from titania were tested as toxic agents on different cancer cell lines. The sol-gel method was used for the synthesis and surface functionalization of the titania, as well as for loading the copper complexes, all in a single step. The resultant Cu/F-TiO2 materials were characterized by several techniques. An in vitro releasing test was developed using an aqueous medium. Different concentrations (15.6-1000 A mu g mL(-1)) of each copper complex, those loaded on titania (Cu/F-TiO2), functionalized titania, and cis-Pt as a reference material, were incubated on RG2, C6, U373, and B16 cancer cell lines for 24 h. The morphology of functionalized titania and the different Cu/F-TiO2 materials obtained consists of aggregated nanoparticles, which generate mesopores. The amorphous phase (in dominant proportion) and the anatase phase were the structures identified through the X-ray diffraction profiles. These results agree with high-resolution transmission electron microscopy. Theoretical studies indicate that the copper compounds were released by a Fickian diffusion mechanism. It was found that independently of the copper complex and also the cell line used, low concentrations of each copper compound were sufficient to kill almost 100 % of cancer cells. When the cancer cells were treated with increasing concentrations of the Cu/F-TiO2 materials the number of survival cells decreased. Both copper complexes alone as well as those loaded on TiO2 had higher toxic effect than cis-Pt.