Killing of cancer cell line by photoexcitation of folic acid-modified titanium dioxide nanoparticles

Folic acid (FA) was coupled onto titanium dioxide nanoparticles to provide a specificity of cell targeting. Modification was confirmed by infrared absorption spectra and zeta potential that suggested a formation of linkage between carboxylic acid of FA and titanium dioxide. The surface attachment of folic acid did not cause a significantly change in particles size, but led to a reduction of photocatalytic activity of TiO 2 . The FA-modified TiO 2 nanoparticles could be internalized by cells at a much faster rate than the unmodified TiO 2 , due to the mediation of folate receptor on the cancer cells. The UV irradiation caused death of HeLa cells pretreated with FA-modified TiO 2 more effectively than that of HeLa cells treated with unmodified TiO 2 . Results suggest that to modify TiO 2 with folic acid using appropriately the FA-to-TiO 2 mass ratio of 0.2 could yield nanoparticles having higher cytotoxicity under photoexcitation. Photocatalytic TiO 2 nanoparticles could not only damage to cellular components including plasma membranes leading to cell nucrosis but also induce the programming cell death. Results from flow cytometry-based analysis indicated that the mechanism of cell death was a combination of necrosis and apoptosis.