Anti-tumor effects of liposome-encapsulated titanium dioxide in nude mice

Anatase particles of titanium dioxide (TiO2) absorb ultraviolet (UV) light which is shorter than 415 nm. Photoexcited TiO2, a strong oxidizer, is expected to inhibit malignant cell growth. Liposomes accelerate endophagocytosis to the cytoplasm of encapsulated materials. In this study, we examined anti-tumor effects of TiO2 and liposome-encapsulated TiO2 (LT) with UVA irradiation by an air pouch cancer model using NBT-II bladder cancer cells, which simulates bladder cancer. Injection of TiO2 or LT into the air pouch was followed by UVA irradiation via the opened pouch. Tumors of TiO2 + UVA and LT + UVA groups showed more pronounced necrotic areas, apoptotic indices, nitrotyrosine formation, tumor growth inhibition and increased survival compared with control groups. Especially the LT + UVA group showed more remarkable anti-tumoral effects than the TiO2 + UVA group, which was associated with higher TiO2 incorporation. These findings suggest that LT might be more effective than noncoated TiO2 in the treatment of bladder cancer.