The antitumor activity of irradiated Degussa P25 TiO(2) nanoparticles (anatase/rutile ratio of about 3:1; average diameters of the anatase and rutile particles estimated at 25 and 85 nm, respectively) was investigated in vitro: sarcoma cells killing, lipooxygenase enzymic action inhibition; and ex vivo: human platelets aggregation, in order to get insight into the possible effects of photoexcited titanium dioxide in cancer treatment. Irradiated and non-irradiated TiO(2) concentrations (varying from 0.8 mu M to 1000 mu M) did not show any toxicity when cultured with fibroblasts MRC-5. In vitro cultured sarcoma cells, derived and isolated from sarcoma tumors produced on experimental Wistar rats after their treatment with benzo-[a]-pyrene, were completely killed in the presence of TiO(2) (40 mu/ml). The antimetastatic capability of titanium oxide in haematogenous spread of cancer cells was also confirmed in tests involving fresh human platelets with a number of different stimulators, including sarcoma cells, platelet activated factor (PAF), diphosphoric adenosine (ADP) and arachidonic acid. Sarcoma cells-human platelets mixtures irradiated by UV-C in the presence of TiO(2) showed a significant decrease in aggregation, effect that becomes more pronounced by increasing the titania concentration. Platelet aggregation triggered by PAF and arachidonate addition was totally inhibited by photoexcited TiO(2), while partial inhibition of aggregation triggered by ADP was observed. Addition of TiO(2) followed by irradiation with UV-C also resulted in an important decrease of lipooxygenase enzyme's activity. (C) 2010 Elsevier B.V. All rights reserved.