Characteristics of Multiwall Carbon Nanotubes for an Intratracheal Instillation Study with Rats

Abstract

Much concern has been raised over the health consequences of workers exposed to carbon nanotubes. In order to characterize multi-wall carbon nanotubes (MWCNT) suspended in a phosphate-buffered saline containing 0.1% Tween 80 for an intratracheal instillation study.

Pulmonary Toxicity of Intratracheally Instilled Multiwall Carbon Nanotubes in Male Fischer 344 Rats

“…Persistence of MWCNT fibers in the alveolar interstitium might allow sufficient time for migration of the fibers through the pulmonary lymphatic pathway adjacent to the pleural cavity. Deposition of MWCNT in the pulmonary lymphatics such as BALT suggests that the dispersed MWCNT fibers might migrate from the alveolar interstitium to the pleura and exert asbestoslike lung pathogenicity in the pleural cavity, as hypothesized by Poland et al 7) The mean length and width of MWCNT fibers used in the present study were 5.0 m m and 88 nm, respectively, with an averaged aspect ratio of 57, and fibers longer than 5 m m were found to occupy 38.9% of total fibers 22) , suggesting a similarity in size and shape of MWCNT and asbestos fibers. Peritoneal and intrascrotal administrations of MWCNT fibers having an equal length and width as those used in the present study are reported to have induced peritoneal mesotheliomas in male p53 gene-deficient mice 5) and intact male F344 rats 6) , respectively.…”

“…In the separate paper 22) , we reported that the 20-min and additional 30-s ultrasonication and intratracheal instillation of MWCNT suspended in PBS containing 0.1% Tween 80 allowed good dispersion of MWCNT fibers in the suspension at the time of intratracheal instillation with a microspray cannula. Besides, the well-dispersed MWCNT fibers were partly engulfed by alveolar macrophages in the alveolar area of MWCNTdosed rats sacrificed on Day 1 after instillation, suggesting the occurrence of frustrated phagocytosis or incomplete phagocytosis, as proposed by Poland et al 7) and Hubbs et al 24) , respectively.…”

“…Since neither MWCNT nor α -quartz is water-soluble or wettable, these test substances were suspended in phosphate-buffered saline (PBS) containing 0.1% Tween 80 as a colloidal dispersant and subjected to ultrasonication for 20 min with an ultrasonic homogenizer (VP-30S, 20 kHz, 300 W, TAITEC Co., Ltd, Tokyo, Japan). The size distribution of the MWCNT in the suspension was measured by both a dynamic light scattering size measurement (DLS) and scanning electron microscopic (SEM) observation 22) . Briefly, the DLS measurement showed that the median hydrodynamic diameter of MWCNT in the suspension after 20-min ultrasonication ranged below 1.0 m m. The SEM observation revealed that the mean length and width of the MWCNT fibers were 5.0 m m and 88 nm, respectively, and that fibers longer than 5.0 m m occupied 38.9% of the total fibers counted.…”

“…Briefly, the DLS measurement showed that the median hydrodynamic diameter of MWCNT in the suspension after 20-min ultrasonication ranged below 1.0 m m. The SEM observation revealed that the mean length and width of the MWCNT fibers were 5.0 m m and 88 nm, respectively, and that fibers longer than 5.0 m m occupied 38.9% of the total fibers counted. The MWCNT was found to contain 4,400 ppm (wt/wt) iron, 48 ppm chromium and 17 ppm nickel by graphite furnace atomic absorption spectrometric analysis, and these levels of metals were considered not to elicit any positive pulmonary responses 22) . Measurement of endotoxin levels in the PBS-Tween 80 suspending MWCNT or α -quartz was commissioned to Japan SLC, Ltd. (Tokyo, Japan).…”

“…The affected lungs were examined for both lung histopathology and biochemical and cytological analyses of bronchoalveolar lavage (BAL) fluid, with reference to the lung lesions and their severities induced by intratracheally instilled α -quartz as a positive control. The results of the dose characteristics of MWCNT in the suspension were accepted for publication in this Journal as a separate paper 22) .…”