Superoxide ions generation. O2-· anions generation by T-Lite DA, T-Lite DL, and pure TiO2 nanoparticles measured using the XTT combined or not with the SOD chemical probes. Measurements were performed at 470 nm. Error bars indicate the standard deviation from the mean (n = 3). XTT formazan production = [Abs sample(t)-Abs sample(t0)]-[Abs solvent(t)-Abs solvent(t0)].