Investigation of antibacterial activity and related mechanism of a series of nano-Mg(OH)₂.

Here we reported the antibacterial effect and related mechanism of three nano-Mg(OH)(2) slurries using Escherichia coli as model bacteria. X-ray diffraction (XRD), scanning electron microscopy (SEM) and laser particle size analysis revealed that the as-synthesized Mg(OH)(2)_(MgCl2), Mg(OH)(2)_(MgSO4) and Mg(OH)(2)_(MgO) are all composed by nanoflakes with different sizes, and their aggregates in water are 5.5, 4.5, and 1.2 μm, respectively. Bactericidal tests showed that the antibacterial efficiency is conversely correlated with the size of Mg(OH)(2) aggregates. Transmission electron microscopy (TEM) observation have not provided evidence of cellular internalization, however, the antibacterial effect is positive correlation to the loss of integrity of cell walls. SEM and zeta potential analysis revealed that the adhering ability of Mg(OH)(2) on the bacterial surface is Mg(OH)(2)_(MgCl2) > Mg(OH)(2)_(MgSO4) > Mg(OH)(2)_(MgO), indicating the toxicity of Mg(OH)(2) may be caused by the electrostatic interaction-induced external adsorption. Confocal laser scanning microscopy (CLSM) further revealed that the adhering of Mg(OH)(2) on the bacterial surface could increase the permeability of cell membranes. Taken together, the antibacterial mechanism of nano-Mg(OH)(2) could be as follows: nano-Mg(OH)(2) adsorbed on the bacterial surface by charge attraction first, and then destroyed the integrity of cell walls, which resulting in the final death of bacteria.