Size Dependent Dissolution of Silver Nanoparticles in Human Monocytic/Macrophage-Like U937 Cells and Speciation by Single Particle-Inductively Coupled Plasma-Mass Spectrometry (SP-ICP-MS)

Abstract

Various analytical methods have been employed to assess the nanoparticle (NP) toxicity and to better understand cell interactions. In this study, a rapid single particle – inductively coupled plasma – mass spectrometry (SP-ICP-MS) method is utilized to evaluate silver nanoparticle (AgNP) uptake by human monocytic/macrophage-like U937 cells. For this purpose, the cells were incubated with 40 nm and 70 nm AgNPs at 100 and 1000 ng mL−1 for 48 h. After cells were incubated with 40 nm and 70 nm AgNPs at the lower dosage (100 ng mL−1), the silver mass per cell was determined to be 1.5 ± 0.1 fg/cell (approximately 4 nanoparticles) and 3.6 ± 0.1 fg/cell (approximately 2 nanoparticles), respectively. Furthermore, for 100 ng mL−1 AgNP exposure, the results showed that silver was present both in the medium and in cell lysate only as AgNP. However, when cells were treated with 40 nm and 70 nm AgNPs at 1000 ng mL−1, approximately 10% and 40% of the total Ag concentration in cell lysate were AgNP and the rest was Ag+, while AgNP was the only species in the medium. The results show that 40 nm AgNP dissolved significantly more in cells compared to 70 nm AgNP. Moreover, ultracentrifugation, ICP-MS, and field emission scanning electron microscopy (FE-SEM) were employed with scanning transmission electron microscopy (STEM) to validate and confirm the SP-ICP-MS results.