Carbon Nanomaterials Promote M1/M2 Macrophage Activation

Toxic effects of certain carbon nanomaterials (CNM) have been observed in several exposure scenarios both in vivo and in vitro. However, most of the data currently available has been generated in a high-dose/acute exposure setup, limiting the understanding of their immunomodulatory mechanisms. Here, macrophage-like THP-1 cells, exposed to ten different CNM for 48 h in low-cytotoxic concentration of 10 mu g mL(-1), are characterized by secretion of different cytokines and global transcriptional changes. Subsequently, the relationships between cytokine secretion and transcriptional patterns are modeled, highlighting specific pathways related to alternative macrophage activation. Finally, time- and dose-dependent activation of transcription and secretion of M1 marker genes IL-1 beta and tumor necrosis factor, and M2 marker genes IL-10 and CSF1 is confirmed among the three most responsive CNM, with concentrations of 5, 10, and 20 mu g mL(-1) at 24, 48, and 72 h of exposure. These results underline CNM effects on the formation of cell microenvironment and gene expression leading to specific patterns of macrophage polarization. Taken together, these findings imply that, instead of a high and toxic CNM dose, a sub-lethal dose in controlled exposure setup can be utilized to alter the cell microenvironment and program antigen presenting cells, with fascinating implications for novel therapeutic strategies.Peer reviewe

In vivo genotoxicity and inflammatory effects of uncoated and coated CeO2 NPs in mice

P17-045 Ceria nanoparticles (CeO2 NPs) have several industrial applications and pharmacological potential due to their antioxidant properties. However, toxicity data on CeO2 NPs are scarce and show contradictory results. In the present study, uncoated, polyethylene glycol- and citrate-coated CeO2 NPs (4-8 nm) were administrated to C57Bl/6 mice by repeated dose (3×) pharyngeal aspiration using four different doses of each type of NPs (corresponding to 4.4, 8.8, 17.6 and 35.2 µg Ce2+/mouse/aspiration), and sampled 1 and 28 days after the last administration. DNA damage was assessed by the comet assay locally in bronchoalveolar lavage (BAL) and lung cells, and systemically in liver cells. Micronuclei, a biomarker of chromosome damage, were analysed in bone marrow and peripheral blood erythrocytes. Immunotoxicity was evaluated by BAL cell counting. Furthermore, histopathological effects on the lungs and biodistribution of the NPs (analysis of Ce2+ in several organs) were assessed. At 24-h, a significant increase in DNA damage was induced at the highest doses by uncoated and citrate-coated NPs in BAL cells. For these NPs a significant, but non-dose-dependent, effect was observed in lung and liver cells at 28-d. No systemic genotoxic effects were observed with any of the NPs. A dose-dependent accumulation of macrophages and activated lymphocytes was seen in the lungs for all the NPs, although a milder reaction was elicited by the coated NPs. Our findings show that short-term exposure of mice to CeO2 NPs induces pulmonary inflammation, and non-dose-dependent DNA damage, but no systemic genotoxicity. (Funded by the EU FP-7 GUIDEnano, Grant Agreement No.604387)

Free radical scavenging and formation by multi-walled carbon nanotubes in cell free conditions and in human bronchial epithelial cells

Background: Certain multi-walled carbon nanotubes (MWCNTs) have been shown to elicit asbestos-like toxicological effects. To reduce needs for risk assessment it has been suggested that the physicochemical characteristics or reactivity of nanomaterials could be used to predict their hazard. Fibre-shape and ability to generate reactive oxygen species (ROS) are important indicators of high hazard materials. Asbestos is a known ROS generator, while MWCNTs may either produce or scavenge ROS. However, certain biomolecules, such as albumin – used as dispersants in nanomaterial preparation for toxicological testing in vivo and in vitro - may reduce the surface reactivity of nanomaterials. Methods: Here, we investigated the effect of bovine serum albumin (BSA) and cell culture medium with and without BEAS 2B cells on radical formation/scavenging by five MWCNTs, Printex 90 carbon black, crocidolite asbestos, and glass wool, using electron spin resonance (ESR) spectroscopy and linked this to cytotoxic effects measured by trypan blue exclusion assay. In addition, the materials were characterized in the exposure medium (e.g. for hydrodynamic size-distribution and sedimentation rate). Results: The test materials induced highly variable cytotoxic effects which could generally be related to the abundance and characteristics of agglomerates/aggregates and to the rate of sedimentation. All carbon nanomaterials were found to scavenge hydroxyl radicals (•OH) in at least one of the solutions tested. The effect of BSA was different among the materials. Two types of long, needle-like MWCNTs (average diameter >74 and 64.2 nm, average length 5.7 and 4.0 µm, respectively) induced, in addition to a scavenging effect, a dose-dependent formation of a unique, yet unidentified radical in both absence and presence of cells, which also coincided with cytotoxicity. Conclusions: Culture medium and BSA affects scavenging/production of •OH by MWCNTs, Printex 90 carbon black, asbestos and glass-wool. An unidentified radical is generated by two long, needle-like MWCNTs and these two CNTs were more cytotoxic than the other CNTs tested, suggesting that this radical could be related to the adverse effects of MWCNTs

An insight into the effect of rough surfaces and contact orientation on the fretting characteristics of quenched and tempered steel

The effect of a rough, textured surface and contact orientations on the fretting behavior of self-mated martensitic 34CrNiMo6 +QT steel was examined via a large annular flat-on-flat contact. A friction study accompanied by microscopy analyses was performed to provide a clear insight into fretting characteristics. In gross sliding, the rough surface revealed a lower delayed friction peak and the same steady-state friction as the fine-ground smooth one. In partial slip, the stable friction threshold was around 0.5 for both surfaces. The oxidation-abrasion and its combination with adhesion were observed as wear mechanisms in partial slip and gross sliding, respectively.Peer reviewe

Catalysis over zinc-incorporated berlinite (ZnAlPO4) of the methoxycarbonylation of 1,6-hexanediamine with dimethyl carbonate to form dimethylhexane-1,6-dicarbamate

<p>Abstract</p> <p>Background</p> <p>The alkoxycarbonylation of diamines with dialkyl carbonates presents promising route for the synthesis of dicarbamates, one that is potentially 'greener' owing to the lack of a reliance on phosgene. While a few homogeneous catalysts have been reported, no heterogeneous catalyst could be found in the literature for use in the synthesis of dicarbamates from diamines and dialkyl carbonates. Because heterogeneous catalysts are more manageable than homogeneous catalysts as regards separation and recycling, in our study, we hydrothermally synthesized and used pure berlinite (AlPO₄) and zinc-incorporated berlinite (ZnAlPO₄) as heterogeneous catalysts in the production of dimethylhexane-1,6-dicarbamate from 1,6-hexanediamine (HDA) and dimethyl carbonate (DMC). The catalysts were characterized by means of XRD, FT-IR and XPS. Various influencing factors, such as the HDA/DMC molar ratio, reaction temperature, reaction time, and ZnAlPO₄/HDA ratio, were investigated systematically.</p> <p>Results</p> <p>The XRD characterization identified a berlinite structure associated with both the AlPO₄and ZnAlPO₄catalysts. The FT-IR result confirmed the incorporation of zinc into the berlinite framework for ZnAlPO₄. The XPS measurement revealed that the zinc ions in the ZnAlPO₄structure possessed a higher binding energy than those in ZnO, and as a result, a greater electron-attracting ability. It was found that ZnAlPO₄catalyzed the formation of dimethylhexane-1,6-dicarbamate from the methoxycarbonylation of HDA with DMC, while no activity was detected on using AlPO₄. Under optimum reaction conditions (i.e. a DMC/HDA molar ratio of 8:1, reaction temperature of 349 K, reaction time of 8 h, and ZnAlPO₄/HDA ratio of 5 (mg/mmol)), a yield of up to 92.5% of dimethylhexane-1,6-dicarbamate (with almost 100% conversion of HDA) was obtained. Based on these results, a possible mechanism for the methoxycarbonylation over ZnAlPO₄was also proposed.</p> <p>Conclusion</p> <p>As a heterogeneous catalyst ZnAlPO₄berlinite is highly active and selective for the methoxycarbonylation of HDA with DMC. We propose that dimethylhexane-1,6-dicarbamate is formed <it>via </it>a catalytic cycle, which involves activation of the DMC by a key active intermediate species, formed from the coordination of the carbonyl oxygen with Zn(II), as well as a reaction intermediate formed from the nucleophilic attack of the amino group on the carbonyl carbon.</p

Inhalation of rod-like carbon nanotubes causes unconventional allergic airway inflammation

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