Development of a new cancer therapy using photoexcited semiconductor particles

光激发tio2半导体粒子具有很强的氧化还原能力，可以驱动多种化学反应。为了探讨这种效应在癌症治疗中的可能应用，我们在体外和体内研究了光激发tio2颗粒的抗肿瘤活性。体外培养的人癌细胞，如T-24人膀胱癌细胞和HeLa细胞，在500 W Hg灯的光照射下，在tio2存在下完全死亡。相比之下，没有光照射的tio2处理几乎没有观察到细胞死亡。与单独接受tio2或光照射的裸鼠相比，光激发的tio2颗粒也显著抑制了人癌细胞的生长。在l -色氨酸和过氧化氢酶存在的情况下，光激发tio2颗粒引起的细胞死亡有明显的保护作用。这些分子分别是羟基自由基（OH^）的猝灭剂和过氧化氢（H_2O_2）的清除剂，表明细胞是被OH^杀死的。和由光激发tio2粒子产生的H_2O_2。在这些实验观察的基础上，可以得出结论，在紫外光照射下，二氧化钛的细胞杀伤作用可以作为抗癌方式之一。

Photo-excited Ti02 semiconductor particles can drive various chemical reactions due to their strong oxidizing and reducing ability. To investigate the possible use of this effect for cancer treatment, the anti-tumor activity of photo-excited Ti02 particles were studied in vitro and in vivo. Human cancer cells, like T-24 human bladder cancer cells and HeLa cells, cultured in vitro were completely killed in the presence of Ti02 with photo-irradiation by a 500 W Hg lamp. In cotrast, very little cell death was observed by Ti02 treatment without photo-irradiation. Photoexcited Ti02 particles also suppressed growth of human cancer cells implanted in nude mice significantly, compared with those receiving Ti02 alone or photo-irradiation alone. The cell death caused by photo-excited Ti02 particles was significantly protected in the presence of L-tryptophan and catalase. These molecules are quenchers of hydroxyl radicals(OH^.) and scavengers of hydrogen peroxide (H_2O_2), respectively, suggesting that the cells were killed by the OH^. and H_2O_2 produced from photo-excited Ti02 particles. On the basis of these experimental observation, it can concluded that the cell killing effect of Ti02 under UV light irradiation could be adopted as one of anti-cancer modality.