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 ).