The recent surge in graphene research, since its liquid phase monolayer isolation and characterization in 2004, has led to advancements which are accelerating the exploration of alternative 2D materials such as molybdenum disulphide (MoS 2 ), whose unique physicochemical properties can be exploited in applications ranging from cutting edge electronic devices to nanomedicine. However, to assess any potential impact on human health and the environment, the need to understand the bio-interaction of MoS 2 at a cellular and subcellular level is critical. Notably, it is important to assess such potential impacts of materials which are produced by large scale production techniques, rather than research grade materials.The aim of this study was to explore cytotoxicity, cellular uptake and inflammatory responses in established cell-lines that mimic different potential exposure routes samples. Therefore, the inflammatory response of the cells to the MoS 2 or endotoxin contamination was interrogated using a 10-plex ELISA which illustrates cytokine production.The experiments carried out using wild-type and endotoxin hyporesponsive bone marrow derived dendritic cells confirmed that the inflammatory responses result from a combination of endotoxin contamination, the MoS 2 nanomaterials themselves, and the stabilizing surfactant.

Mercury emissions from artisanal and small-scale gold mining throughout the Global South exceed coal combustion as the largest global source of mercury. We examined mercury deposition and storage in an area of the Peruvian Amazon heavily impacted by artisanal gold mining. Intact forests in the Peruvian Amazon near gold mining receive extremely high inputs of mercury and experience elevated total mercury and methylmercury in the atmosphere, canopy foliage, and soils. Here we show for the first time that an intact forest canopy near artisanal gold mining intercepts large amounts of particulate and gaseous mercury, at a rate proportional with total leaf area. We document substantial mercury accumulation in soils, biomass, and resident songbirds in some of the Amazon’s most protected and biodiverse areas, raising important questions about how mercury pollution may constrain modern and future conservation efforts in these tropical ecosystems.

In-vitro localisation and degradation of few-layer MoS2 submicrometric plates in human macrophage-like cells: a label free Raman micro-spectroscopic study

Understanding the correlation between the physico-chemical properties of carbonaceous nanomaterials and how these properties impact on cells and subcelluar mechanisms is critical to their risk assessment and safe translation into newly engineered devices. Here the toxicity, uptake and catabolic response of primary human macrophages to pristine graphene (PG) and pristine single walled carbon nanotubes (pSWCNT) are explored, compared and contrasted. The nanomaterial toxicity was assessed using three complementary techniques (live-dead assay, real time impedance technique and confocal microscopic analysis), all of which indicated no signs of acute cytotoxicity in response to PG or pSWCNT. Transmission electron microscopy (TEM) demonstrated that PG was phagocytosed by the cells into single membrane lysosomal vesicles, whereas the primary macrophages exposed to pSWCNT contained many double membrane vesicles indicative of an autophagic response. These distinct catabolic pathways were further verified by biochemical and microscopic techniques. Raman spectroscopic mapping was used to explore the nanomaterial uptake and distribution. Based on the G-band, significant uptake and accumulation of the PG in discrete vesicles was recorded, whereas the pSWCNT were not taken up to the same extent. Thermogravimetric analysis (TGA) of the cells treated with PG revealed that ~ 20-30% of the remaining dry mass was made up of PG. No detectable amount of pSWCNT was recorded using TGA. TEM analysis confirmed that PG was still graphitic even after 24 hours of accumulation in the lysosomal compartments. In conclusion, these two nanomaterials with similar surface chemistries but unique geometries differ significantly in their uptake mechanisms and subsequently induced lysosomal and autophagic catabolic pathways in human primary macrophages.

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