Development of a Mass Spectrometry Imaging Method for Detecting and Mapping Graphene Oxide Nanoparticles in Rodent Tissues.

Graphene-based nanoparticles are continuously being developed for biomedical applications, and their use raises concerns about their environmental and biological impact. In the literature, some imaging techniques based on fluorescence and radioimaging have been used to explore their fate in vivo. Here, we report on the use of label-free mass spectrometry and mass spectrometry imaging (MSI) for graphene oxide (GO) and reduced graphene oxide (rGO) analyses in rodent tissues. Thereby, we extend previous work by focusing on practical questions to obtain reliable and meaningful images. Specific radical anionic carbon clusters ranging from C2-• to C9-• were observed for both GO and rGO species, with a base peak at m/z 72 under negative laser desorption ionization mass spectrometry (LDI-MS) conditions. Extension to an LDI-MSI method was then performed, thus enabling the efficient detection of GO nanoparticles in lung tissue sections of previously exposed mice. The possibility of quantifying those nanoparticles on tissue sections has also been investigated. Two different ways of building calibration curves (i.e., GO suspensions spotted on tissue sections, or added to lung tissue homogenates) were evaluated and returned similar results, with linear dynamic concentration ranges over at least 2 orders of magnitude. Moreover, intra- and inter-day precision studies have been assessed, with relative standard deviation below 25% for each concentration point of a calibration curve. In conclusion, our study confirms that LDI-MSI is a relevant approach for biodistribution studies of carbon-based nanoparticles, as quantification can be achieved, provided that nanoparticle suspension and manufacturing are carefully controlled.

Carbon nanotubes, but not spherical nanoparticles, block autophagy by a shape-related targeting of lysosomes in murine macrophages.

Nanoparticles (NPs) can be toxic, depending on their physico-chemical characteristics. Macroautophagy/autophagy could represent a potential underlying mechanism of this toxicity. We therefore set up a study aimed to characterize in depth the effects, on autophagy, of macrophage exposure to NPs, with a particular attention paid to the role of NP physico-chemical characteristics (specifically chemical composition, shape, size, length, crystal phase, and/or surface properties). We demonstrate that exposure to carbon nanotubes (CNT) but not to spherical NPs leads to the blockage of the autophagic flux. We further identified lysosomal dysfunction, in association with the downregulation of SNAPIN expression, as the underlying mechanism responsible for the CNT-induced autophagy blockade. These results identify for the first time the shape as a major determinant of the interaction of NPs with the autophagy pathway. Moreover, identifying the lysosomes and SNAPIN as primary targets of MWCNT toxicity opens new directions in the interpretation and understanding of nanomaterial toxicity.