High aspect ratio materials: role of surface chemistry vs. length in the historical “long and short amosite asbestos fibers”

Abstract

In nanotoxicology the question arises whether high aspect ratio materials should be regarded as potentially pathogenic like asbestos, merely on the base of their biopersistence and length to diameter ratio. A higher pathogenicity of long asbestos fibers is associated to their slower clearance and frustrated phagocytosis. In the past decades, two amosite fibers were prepared and studied to confirm the role of fiber length in asbestos toxicity. Long fiber amosite (LFA) and short fiber amosite (SFA) have here been revisited, to check differences in their surface properties, known to modulate the biological responses elicited. We report: (i) micromorphology (abundance of exposed cylindrical vs. truncated surfaces; (ii) surface reactivity (oxidation and coordination state of surface iron, free radical generation and oxidizing potential); (iii) activation of nitric oxide (NO) synthase in lung epithelial cells, as representative of an inflammatory cell response. LFA shows a higher free radical yield, stimulates, more than SFA, NO production by cells and reacts with ascorbic acid, thus depriving the lung lining layer of its antioxidant defenses. The higher activity of LFA than SFA is ascribed to the presence of Fe2+ ions poorly coordinated to the surface. SFA shows only a large number of loosely bound Fe3+ ions, pristine Fe2+ ions having been oxidized during the grinding process converting LFA into SFA. Several factors determine a higher toxicity of LFA than SFA, beside length. The lesson from asbestos indicates that other features besides aspect ratio contribute to the pathogenic potential of a fiber type. All these aspects should be considered when predicting the possible hazard associated to any new fibrous material proposed to the market, let alone nanofibers.

Free-Radical Chemistry as a Means to Evaluate Lunar Dust Health Hazard in View of Future Missions to the Moon

“…Similar to what is observed for other minerals with redox-active TMI (e.g., asbestos- Tomatis et al, 2010;Turci et al, 2013), the reactivity of JSC-1A-vf toward C-H bond in the presence of AA is largely increased with respect to experiments carried out in a nonreducing environment (phosphate buffer only). Such an increased reactivity indicates that redox-active TMI-likely iron-at the surface of JSC-1A-vf minerals are easily reduced and their radical reactivity enhanced.…”

“…Surface iron sites are activated following reduction by AA and become the active center for the release of carbon-centered radicals (Martra et al, 2003;Tomatis et al, 2010). To explore the occurrence of such redox sites in JSC-1A-vf, AA (3 mM) was added to the buffered suspension of JSC-1A-vf containing the formate anion and the spin trapping (DMPO).…”

Length-Dependent Retention of Carbon Nanotubes in the Pleural Space of Mice Initiates Sustained Inflammation and Progressive Fibrosis on the Parietal Pleura

“…There have been suggestions that CNTs can undergo a degree of dissolution depending on their form 42,43 ; thus, the retention/translocation kinetics of long CNTs from the pleural space could change over time if the CNTs undergo any biodissolution. Recently, Tomatis et al 44 reported that the greater toxicity of long asbestos fibers when compared with short asbestos fibers could be attributed to several factors other than length, including greater free radical production and reactive surface. Although these factors may give added toxicity to any fiber, we contend that the properties defined by the fiber pathogenicity paradigm (ie, length, thinness, and biopersistence) remain the primary attributes that a fiber must possess to elicit a pathogenic response.…”

Endocytosis and exocytosis of nanoparticles in mammalian cells

“…18 In particular, the cells internalize nutrients and signaling molecules to obtain energy and interact with other cells, respectively. The endocytosis pathways are typically classified into clathrin-and caveolaemediated endocytosis, phagocytosis, macropinocytosis, and pinocytosis ( [19][20][21] These endocytosis pathways are the most important pathways for the internalization of nanoparticles into cells because the nanoparticles are directly coated with the plasma proteins when exposed to physiological solutions. The phagocytosis pathway is used when phagocytic cells internalize foreign materials with sizes larger than 0.5 μm.…”