Considerations using silver nitrate as a reference for in vitro tests with silver nanoparticles

Abstract

Most in vitro tests regarding the cellular toxicology of nanoparticulate metals compare particle to associated metal ion exposure. However, it is also a fact, that for example silver ions are reduced by sugars or transformed to silver chloride by chloride salts which are abundant components of cell culture media. These reactions are likely to either complicate or even invalidate comparisons between effects of ions and particles. Here, we present a fast and quantitative method to determine particle formation and numbers in different cell culture media with non-destructive small-angle X-ray scattering (SAXS). Silver nitrate with a concentration of 25μgAgmL−1 was dissolved for up to 24h at 37°C in Dulbeccos Modified Eagle Medium (DMEM) with and without 10% fetal bovine serum (FBS) and a solution of D-glucose (4.5μgmL−1), respectively. Silver nanoparticles were observed in all solutions after 5min. The cell culture media displayed a limited particle-growth. FBS showed an effect on the polydispersity of the generated particles but after 5min the overall particle size was nearly equal in FBS and non FBS supplemented medium. Particles in D-glucose were precipitating after 10min. Particulate silver concentration was between 3 and 4μgmL−1 in both cell culture media (CCM). These results should be taken into account when performing silver ion-toxicity experiments in relevant media.