3.9. Effect of the amount of metal-loaded organoclay
Deeper insights through different amounts of metal-loaded organoclays ranging from 1 to 9 mg were achieved to confirm the effect of MNP insertion on their antibacterial activity. A first overview of the obtained results revealed that the bacterial growth was inhibited after an incubation with 1 mg antimicrobial agents (Fig. 3.b) . The average diameter of the inhibition zone was of 2-2.3 cm for Cu2+/H20@NaMt and 0.8-2 cm Ag+/H20@NaMt (Table S2 ). This result can be ascribed to the strong antibacterial capacity of metal-loaded organoclay matrices on E. coli and Bacillus . The appearance of antibacterial activity seems due to the metal incorporation, regardless to its oxidation state. In other words, the mere presence of metal species appears to promote an antibacterial activity. This is well argued by the fact that no antibacterial activity was found for both clay mineral and polyol alone (Fig. 3.a) . Therefore, the biocide effect of the as-synthesized samples should be due to the action of both MNPs and metal cations. The diameter of the inhibition zone of both strains E. coli and B. subtilis increased almost proportionally with increasing amount of bactericidal agents up to a certain level. Maximal values of 2.5 and 3.5 cm for 9 mg of Cu2+/NaMt@H20 and of 2.4 and 3 cm for the same amount of Cu0/NaMt@H20 against E. coli and B. subtilis, were respectively attained (Table S2 ).