Biocide activity of diatom-silver nanocomposite

Diatom-nAg composites containing 1 wt.% of metallic silver nanoparticles (≤ 20 nm) have been obtained by a colloidal route and chemical reduction. This nanostructured powder has proved to be a selective green inorganic biocide which reduces the starting concentrations of Escherichia coli and Micrococcus luteus cultures by at least 5 orders of magnitude, while completely inactive against yeast. Diatom-nAg can be considered as a selective inorganic biocide particularly suitable for the food and pharmacological sectors. The silver nanoparticles are released from the diatom surface to the liquid media in a controlled manner, reaching a concentration (< 11 ppm) far below the toxicity limit for human cells.