Structural characterization of antifungal CaZn2(OH)6·2H2O nanoparticles obtained via mechanochemical processing.

The establishment of microorganisms and particularly fungi on rock surfaces, which is favored by humid tropical climates, may accelerate the degradation of historical monuments and buildings and thereby cause the irreversible loss of rich cultural heritage. Therefore, it is urgent to search for new ways to preserve such buildings. The in vitro antifungal activity of calcium zinc hydroxide dihydrate [CaZn2(OH)6·2H2O] (CZ) synthesized via the sol-gel method has been previously reported for limestone. The present study reports for the first time, the minimum fungicidal concentration (MFC) of CZ obtained via mechanochemical processing, against diverse fungi involved in biodeterioration processes of limestone and dolostone. We found that CZ nanoparticles had a fungicidal effect on all evaluated fungi, at concentrations of 156-1250 μg/mL. The MFC depends on the number of cells in conidia and the presence of melanin in cell walls. For these reasons, Pestalotiopsis maculans and Curvularia lunata, which had more than four cells and melanin pigmentation, both required a greater CZ concentration (1250 μg/mL) for inhibition, compared with species from the genera Penicillium oxalicum and Aspergillus niger, which had one cell and were strongly inhibited. Thus, CZ nanoparticles are promising candidates for application in treatments to restore the cultural heritage. [ABSTRACT FROM AUTHOR]