Recent study comparing 12 silver NPs showed that there are strong effects on toxicity depending on the coating materials. Neither aggregation size, coating materials themselves- at the concentrations used, nor dissolution of NP explained the observed toxicity pattern, driving us to examine more detailed measurements of the NP surface. We will investigate the stability of the bonds between coating materials and the Ag core as well as the density of coating molecules on the surface of the NP (i.e. number of coating molecules per NP surface area) and relate these measurements to the observed toxicity pattern. On the toxicity side, we are examining cellular alterations and changes in internal sodium concentration. Uptake of silver (total) and biodistribution of AgNPs is also being quantified and compared.