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Received for publication April 29, 2008.
Revised July 14, 2008.
Accepted for publication July 15, 2008.
Intraperitoneal injection of [Gd@C82(OH)22]n nanoparticles decreased activities of enzymes associated with the metabolism of reactive oxygen species (ROS) in the tumor-bearing mice. Several physiologically relevant ROS were directly scavenged by nanoparticles and lipid peroxidation was inhibited in this study. [Gd@C82(OH)22]n nanoparticles significantly reduced the electron spin resonance (ESR) signal of the stable DPPH radical measured by ESR spectroscopy. Similarly, studies using ESR with spin-trapping demonstrated efficient scavenging of superoxide radical anion (O2·-), hydroxyl radical (HO·) and singlet oxygen (1O2) by [Gd@C82(OH)22]n nanoparticles. In vitro studies using liposomes prepared from bovine liver phosphatidylcholine revealed that nanoparticles also had a strong inhibitory effect on lipid peroxidation. Consistent with their ability to scavenge ROS and inhibit lipid peroxidation, we determined that [Gd@C82(OH)22]n nanoparticles also protected cells subjected in vitro to oxidative stress. Studies using human lung adenocarcinoma cells or rat brain capillary endothelial cells demonstrated that [Gd@C82(OH)22]n nanoparticles reduced H2O2-induced ROS formation and mitochondrial damage. [Gd@C82(OH)22]n nanoparticles efficiently inhibited the growth of malignant tumors in vivo. In summary, the results obtained in this study reveal anti-tumor activities of [Gd@C82(OH)22]n nanoparticles in vitro and in vivo. As ROS are known to be implicated in the etiology of a wide range of human diseases, including cancer, the present findings demonstrate that the potent inhibition of [Gd@C82(OH)22]n nanoparticles on tumor growth likely relates with typical capacity of its reactive oxygen species scavenge.
Key words:
Oxidative stress, Mechanisms of cell killing/apoptosis, Resistance