Comparison of the suitability of alkaline or enzymatic sample pre-treatment for characterization of silver nanoparticles in human tissue by single particle ICP-MS

Abstract

To understand potential harmful effects of silver nanoparticles (AgNPs) for the growing fetus, studies dealing with the translocation and accumulation of NPs across the placental barrier are of great importance. Quantitative methods for determination of NP mass and number concentration and their size are required for studying NP accumulation in placental tissue. In the present study, we applied and compared two sample preparation techniques, alkaline and enzymatic treatment, followed by single particle ICP-MS (spICP-MS) analysis, for characterizing AgNPs spiked to human placental tissue. Both sample preparation approaches are currently used for AgNPs in biological tissues but have not been directly compared yet. We showed that the method using enzymatic tissue treatment followed by spICP-MS is efficient for determination of mass and number concentration and size distribution of AgNPs in human placental tissues. Properties of the AgNPs were preserved during enzymatic digestion and comparable with the primary particles. The matrix effect on the determination of Ag sensitivity and transport efficiency in spICP-MS analysis was systematically evaluated as well. The method was applied to human placenta, exposed to AgNPs with two different surface modifications: 27 nm polyethylene glycol (AgPEG NPs) or 34 nm sodium carboxylate groups (AgCOONa NPs) in an ex vivo human placental perfusion model. The Ag mass concentration obtained with spICP-MS following enzymatic sample pretreatment was not significantly different from the Ag concentration obtained by conventional ICP-MS analysis of acid digested tissue. With this we confirmed the ability of the procedure to quantitatively characterize AgNPs accumulated in human tissue under realistic exposure scenario.