PVP-capped silver nanoparticles with a diameter of the metallic core of 70 nm,
a hydrodynamic diameter of 120 nm and a zeta potential of −20 mV were prepared
and investigated with regard to their biological activity. This review
summarizes the physicochemical properties (dissolution, protein adsorption,
dispersability) of these nanoparticles and the cellular consequences of the
exposure of a broad range of biological test systems to this defined type of
silver nanoparticles. Silver nanoparticles dissolve in water in the presence
of oxygen. In addition, in biological media (i.e., in the presence of
proteins) the surface of silver nanoparticles is rapidly coated by a protein
corona that influences their physicochemical and biological properties
including cellular uptake. Silver nanoparticles are taken up by cell-type
specific endocytosis pathways as demonstrated for hMSC, primary T-cells,
primary monocytes, and astrocytes. A visualization of particles inside cells
is possible by X-ray microscopy, fluorescence microscopy, and combined FIB/SEM
analysis. By staining organelles, their localization inside the cell can be
additionally determined. While primary brain astrocytes are shown to be fairly
tolerant toward silver nanoparticles, silver nanoparticles induce the
formation of DNA double-strand-breaks (DSB) and lead to chromosomal
aberrations and sister-chromatid exchanges in Chinese hamster fibroblast cell
lines (CHO9, K1, V79B). An exposure of rats to silver nanoparticles in vivo
induced a moderate pulmonary toxicity, however, only at rather high
concentrations. The same was found in precision-cut lung slices of rats in
which silver nanoparticles remained mainly at the tissue surface. In a human
3D triple-cell culture model consisting of three cell types (alveolar
epithelial cells, macrophages, and dendritic cells), adverse effects were also
only found at high silver concentrations. The silver ions that are released
from silver nanoparticles may be harmful to skin with disrupted barrier (e.g.,
wounds) and induce oxidative stress in skin cells (HaCaT). In conclusion, the
data obtained on the effects of this well-defined type of silver nanoparticles
on various biological systems clearly demonstrate that cell-type specific
properties as well as experimental conditions determine the biocompatibility
of and the cellular responses to an exposure with silver nanoparticles