Fig. 1

CoNPs induced Balb/3T3 cell death, while ALA significantly inhibited its cytotoxicity. a The cells were incubated with CoNPs (400 μM) and ALA (200 μM) for 24 h. The cell morphology became round with smaller volume and the cell nucleus was concentrated in response to CoNPs treatment. Interestingly, ALA could reverse these changes induced by CoNPs(40X). b ALA exhibited low cytotoxicity toward Balb/3T3 cells, and it could significantly reduce cell activity only when its concentration is greater than 1200 μM. c CoNPs induced cytotoxicity in both dose- and time-dependent manner. d ALA could reverse the cytotoxicity induced by CoNPs. All the data were expressed as mean ± SD of three independent experiments performed in triplicates. (*p < 0.01, #p < 0.05 vs. control, **p < 0.01 vs. cobalt group)