(87f) Size-Dependent Cytotoxicity of Nanosilver: Effect of Released Ag+ Ions

Silver nanoparticles (nanosilver) are broadly used today in textiles, food packaging, household devices and in bioapplications prompting for a better understanding of their toxicity and biological interactions [1]. However, the cytotoxicity mechanism of nanosilver is still not clear as limitations regarding its controlled synthesis hinder such investigations. Here, nanosilver with closely controlled size (from 5.7 to 16.8 nm) immobilized on nanostructured silica without any coating was produced by flame synthesis [2,3]. Its dispersibility in aqueous solutions was facilitated by the presence of silica, and therefore, the Ag⁺ ion release of this nanosilver was not inhibited by surface coatings [4,5]. Detailed physicochemical characterization of these nanoparticles with X-ray diffraction, N₂ adsorption and electron microscopy revealed the size tunability. Smaller nanosilver released larger fractions of its mass as Ag⁺ ions upon its dispersion water. This strongly influenced the cytotoxicity of such nanosilver upon incubation with murine macrophages, which was assessed by monitoring their mitochondrial activity. The nanosilver size dictated its mode of cytotoxic activity. The toxicity of small nanosilver that released high fractions of Ag⁺ was mostly mediated by the released ions. In the case of large nanosilver, which released only minimal fractions of Ag⁺, the toxicity was attributed to both the released ions but also to the direct nanoparticle-cell contact. The nanosilver behavior when incubated with murine macrophages was also monitored with dark-field and hyperspectral imaging microscopy. It was found that nanosilver tends to agglomerate upon interacting with cells.

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