extremely significantP<0.001
The statistical analysis of mean difference of the purplish red halo diameters under different H 2 O 2 concentrations showed that the increase of the halo diameter was extremely significant (P<0.001) with the increase of H 2 O 2 concentration from 0 to 160 μM, but not significant (P>0.05) with the further increase of H 2 O 2 concentration from 160 μM to 250 μM (Supplementary Table S1 ).