PW cells were treated with 0, 1.25, 2.5, 5, and 10 μg/ml of Nano-Co for 6 h (A and B) or treated with 5 μg/ml of Nano-Co for 3, 6, and 12 h (C and D). Cells without particle treatment were used as the control. (A and C) show the results of a single Western blot experiment. (B and D) represent normalized band densitometry readings averaged from three independent experiments ± SD of Western results. * Significant difference as compared with the control, p<0.05.