Pathology and Physiology Research Branch, Health Effects Laboratory Division, National Institute for Occupational Safety and Health, Morgantown, WV, USA.
Part Fibre Toxicol. 2012 Apr 10;9:10. doi: 10.1186/1743-8977-9-10.
Carbon nanotubes (CNT) and carbon nanofibers (CNF) are allotropes of carbon featuring fibrous morphology. The dimensions and high aspect ratio of CNT and CNF have prompted the comparison with naturally occurring asbestos fibers which are known to be extremely pathogenic. While the toxicity and hazardous outcomes elicited by airborne exposure to single-walled CNT or asbestos have been widely reported, very limited data are currently available describing adverse effects of respirable CNF.
Here, we assessed pulmonary inflammation, fibrosis, oxidative stress markers and systemic immune responses to respirable CNF in comparison to single-walled CNT (SWCNT) and asbestos. Pulmonary inflammatory and fibrogenic responses to CNF, SWCNT and asbestos varied depending upon the agglomeration state of the particles/fibers. Foci of granulomatous lesions and collagen deposition were associated with dense particle-like SWCNT agglomerates, while no granuloma formation was found following exposure to fiber-like CNF or asbestos. The average thickness of the alveolar connective tissue--a marker of interstitial fibrosis--was increased 28 days post SWCNT, CNF or asbestos exposure. Exposure to SWCNT, CNF or asbestos resulted in oxidative stress evidenced by accumulations of 4-HNE and carbonylated proteins in the lung tissues. Additionally, local inflammatory and fibrogenic responses were accompanied by modified systemic immunity, as documented by decreased proliferation of splenic T cells ex vivo on day 28 post exposure. The accuracies of assessments of effective surface area for asbestos, SWCNT and CNF (based on geometrical analysis of their agglomeration) versus estimates of mass dose and number of particles were compared as predictors of toxicological outcomes.
We provide evidence that effective surface area along with mass dose rather than specific surface area or particle number are significantly correlated with toxicological responses to carbonaceous fibrous nanoparticles. Therefore, they could be useful dose metrics for risk assessment and management.
碳纳米管（CNT）和碳纳米纤维（CNF）是碳的同素异形体，具有纤维形态。CNT 和 CNF 的尺寸和高纵横比促使人们将其与天然存在的石棉纤维进行比较，而石棉纤维已知具有极强的致病性。虽然空气中单壁 CNT 或石棉的毒性和有害后果已被广泛报道，但目前有关可吸入 CNF 的不良影响的数据非常有限。
在这里，我们评估了可吸入 CNF 与单壁 CNT（SWCNT）和石棉相比对肺部炎症、纤维化、氧化应激标志物和全身免疫反应的影响。CNF、SWCNT 和石棉的肺部炎症和纤维发生反应取决于颗粒/纤维的团聚状态。肉芽肿病变和胶原蛋白沉积的焦点与密集的颗粒状 SWCNT 团聚物有关，而暴露于纤维状 CNF 或石棉后则未发现肉芽肿形成。肺泡结缔组织的平均厚度（间质纤维化的标志物）在 SWCNT、CNF 或石棉暴露 28 天后增加。SWCNT、CNF 或石棉暴露导致肺部组织中 4-HNE 和羰基化蛋白的积累，从而导致氧化应激。此外，局部炎症和纤维发生反应伴随着系统免疫的改变，暴露后 28 天脾 T 细胞的体外增殖减少证明了这一点。
我们提供的证据表明，有效表面积以及质量剂量而不是比表面积或颗粒数与碳质纤维状纳米颗粒的毒性反应显著相关。因此，它们可能是用于风险评估和管理的有用剂量指标。
