The effects of different concentrations of DETA-NO on the metabolic activity of MDA-MB-231 cells were evaluated. Starting with 0.1 μM DETA-NO up to 1500 μM, the cells maintained their viability in the first 24 hours of culture (supplementary fig. ). However, a significant decrease in the metabolic activity was observed after a subsequent culture for further 24 hours, particularly at 50 μM DETA-NO upwards.