Speciation of gold nanoparticles and low-molecular gold species in Wistar rat tissues by HPLC coupled to ICP-MS

Gold nanoparticles (Au NPs) are widely used today in a broad range of applications like electronics, sensors, catalysis and especially in biomedicine. However, the increase in their use has raised concerns about the possible interactions in vivo and the unexpected responses inside humans and other living organisms. Analytical tools that are able to detect their presence in biological samples and also provide information about the presence of dissolved metal ions inside biological samples are, therefore, urgently needed for a proper understanding of the behaviour of these materials. In this work, an HPLC-ICP-MS technique for the determination of Au NPs was adapted to the analysis of tissues from Wistar rats after intraperitoneal injection of 10 nm Au NPs. This technique allows the detection of Au NPs and low-molecular Au species, permitting the detection and monitoring of potential degradation processes. Alkaline and enzymatic digestions were tested to solubilize the particles and to verify their stability during the extraction process. Enzymatic digestion with proteinase K over 14 h was found to be suitable for the extraction of the Au species with recovery rates of about 91%. Finally, the method was applied to the analysis of liver and spleen samples. Significant abundances of low-molecular Au species were detected (around 30%). This observation suggested that a degradation process played a pivotal role during the transport and accumulation of Au NPs that were intraperitoneally injected into Wistar rats.