We thus posit that the size dependent toxicity relates to the intra cellular Bortezomib order release of Ag ions. When we attempted to mimic one intracellular compartment, the lysosome, by using artificial lysosomal fluid, very little release was ob served. This is explained by the severe agglomeration that takes place in this solution due to the very high ionic strength since low pH is known to cause higher Ag release. In addition, ALF does not contain any pro teins that can serve to stabilize the particles and we con clude that mimicking various intracellular compartments is challenging. Previous studies have shown that Ag ions interfere with cellular functions by interacting with the thiol and amino groups of biomolecules, thus provid ing an explanation for the toxicity.

Ag release has also been reported to govern the toxicity of AgNPs towards bacteria, where the particles act as a vehicle for Ag deliv ery. In the same study the antibacterial effect was hin dered under anaerobic conditions. Inhibitors,Modulators,Libraries Moreover, AgNPs with higher Ag release were shown to be more toxic in Caenorhabditis Inhibitors,Modulators,Libraries elegans. In all, this suggests that AgNPs may change the transport rate of Ag ions into cells and organisms and that subsequently released Ag ions exert the detrimental effects. Conclusion The present study addresses aspects that often are over looked in nanotoxicology studies such as careful time dependent characterization of agglomeration and ion release. The study clearly shows size dependent Inhibitors,Modulators,Libraries cytotox icity of AgNPs since only the 10 nm particles affected the cell Inhibitors,Modulators,Libraries viability of human lung cells.

Despite differences in ag glomeration Inhibitors,Modulators,Libraries of the citrate and PVP coated 10 nm particles, there was no coating dependent example difference in cytotoxicity. Furthermore, our results suggest that intracellular metal release rather than differences in cellular uptake or intra cellular localization is a likely explanation for the observed differences in cytotoxicity. This study thus provides sup port for the so called Trojan horse mechanism by which the particle form facilitates uptake thereby increasing the metal cellular bioavailability. Materials and methods Nanomaterials Five types of AgNPs were investigated in this study. 10 nm OECD PVP BioPure Silver, 10 nm Citrate BioPure Silver, 40 nm Citrate BioPure Silver and 75 nm OECD Citrate BioPure Silver were purchased from NanoComposix, Inc in the form of stock dispersions in Milli Q water or aque ous 2 mM citrate. Uncoated AgNPs in the form of powder were supplied by EV NANO Technology Co Ltd, China. All particles were negative for endotoxin contamination in the lim ulus amebocyte lysate test, performed as described elsewhere.