Application of photoexcited TiO2 semicondoctor to the treatment of bladder cancer

光激发二氧化钛表面具有很强的将水分解为氢和氧的能力。我们研究了这种作用，以便在体外和体内用它来杀死癌细胞。用二氧化钛颗粒和300~400 nm紫外光照射对培养的人膀胱癌T-24细胞有明显的杀伤作用。二氧化钛加紫外线还显著抑制了移植到裸鼠体内的T-24细胞的肿瘤生长。当电极被阳极极化时，培养在二氧化钛电极上的细胞也会在紫外线照射下被杀死，这表明光生孔洞参与了细胞的杀死。在羟基自由基清除剂L-半胱氨酸和过氧化氢酶的存在下，二氧化钛颗粒加紫外光照射对细胞的杀伤作用明显受阻。透射电子显微镜观察表明，二氧化钛颗粒分布在细胞表面和细胞内。这些结果表明，在紫外光照射下，二氧化钛颗粒在表面产生光生孔洞，在细胞内外产生羟基自由基和过氧化氢，然后细胞被这些高度氧化的分子的作用杀死。讨论了光激发二氧化钛粒子作为一种新的抗癌方式在癌症治疗中的可能应用。

A photoexcited titanium dioxide surface has a strong ability to decompose water into hydrogen and oxygen. We have studied this effect in order to use it to kill cancer cells in vitro and in vivo. A distinct cell killing effect was observed on cultured T-24 human bladder cancer cells treated with titanium dioxide particles and 300-400 nm UV light irradiation. Titanium dioxide plus UV light also dramatically suppressed the tumour growth of T-24 cells that were implanted in nude mice. Cells cultured on the titanium dioxide electrode were also killed under UV irradiation when the electrode was anodically polarised, suggesting that photogenerated holes are involved in the cell killing. The cell killing effect caused by titanium dioxide particles plus UV light irradiation was significantly hampered in the presence of L-cysteine and catalase, scavengers of hydroxyl radicals and hydrogen peroxide respectively. Transmission electron microscopic observations showed the titanium dioxide particles to be distributed on the cell surface and inside the cells. These results suggest that titanium dioxide particles under UV light irradiation produced photogenerated holes on the surface yielding hydroxyl radicals and hydrogen peroxide inside or outside the cells and the cells were then killed by the action of these highly oxidising molecules. The possible application of photoexcited titanium dioxide particles to cancer treatment as a new anti-cancer modality is discussed.