Synchrotron-based imaging reveals silver ions trafficking within hepatocytes exposed to silver nanoparticles
Résumé
The widespread use of silver nanoparticles (AgNP) in consumer goods raises concerns about
their toxicity to humans and their impact on environment [1]. AgNP toxicity in cells and
animals has been extensively studied and it has been shown that the toxicity depends upon
the release of Ag(I) ions from the NP[2,3]. Besides, Ag accumulates in liver following AgNP
exposure [4]. In this context, we studied AgNP internalization and fate into hepatocytes. We
made use of a synchrotron nanoprobe to visualize the subcellular distribution of silver. The
combined use of X-ray fluorescence (XRF) microscopy on whole cells and electron
microscopy allowed the discrimination between the nanoparticle form located inside
endosomes and lysosomes and the ionic species that distribute throughout the cell [5].
Besides, synchrotron X-ray absorption spectroscopy showed that Ag(I) recombines with
sulphur in hepatocytes in the form of AgS2 and AgS3 complexes[5,6].
More recently, we developed a nano-XRF method performed on cell sections (Figure 1) that
can be correlated with electron microscopy to reveal Ag(I) species distribution at the
organelle level under long-term exposure to non-toxic concentration of AgNPs. We thus
observed Ag(I) species in different organelles including in the nucleus [7]. This approach
was also used on sections from 3D hepatic cell cultures that mimic liver architecture
including bile canaliculi. XRF allowed to visualize Ag(I) excretion into these intercellular
structures. To get more insights into the fate and effects of AgNPs, these data were
completed with 3D electron microscopy, STEM-EDX and physiology assays. The later
revealed, for the first time, that Ag(I) species translocating into the nucleus can trigger an
endocrine disruptor-like effect. Overall, synchrotron-based imaging was central in our
studies that aim at understanding the fate of nanomaterials in cells and organisms.