An improved superoxide-generating nanodevice for oxidative stress studies in cultured cells

The effects of reactive oxygen species on cells have attracted great attention from both physiological and pathological aspects. Superoxide (O(2)(−)) is the primary reactive oxygen species formed in animals. We previously developed an O(2)(−)-generating nanodevice consisting of NADPH oxidase 2 (Nox2) and modulated activating factors. However, the device was subsequently found to be unstable in a standard culture medium. Here we improved the device in stability by cross-linking. This new nanodevice, Device II, had a half-life of 3 h at 37 °C in the medium. Device II induced cell death in 80% of HEK293 cells after 24 h of incubation. Superoxide dismutase alone did not diminish the effect of the device, but eliminated the effect when used together with catalase, confirming that the cell death was caused by H(2)O(2) derived from O(2)(−). Flow cytometric analyses revealed that Device II induced caspase-3 activation in HEK293 cells, suggesting that the cell death proceeded largely through apoptosis.