An improved dispersion method of multi-wall carbon nanotube for inhalation toxicity studies of experimental animals

Abstract

-A multi-wall carbon nanotube (MWCNT) product Mitsui MWNT-7 is a mixture of dispersed single fibers and their agglomerates/aggregates. In rodents, installation of such mixture induces inflammatory lesions triggered predominantly by the aggregates/agglomerates at the level of terminal bronchiole of the lungs. In human, however, pulmonary toxicity induced by dispersed single fibers that reached the lung alveoli is most important to assess. Therefore, a method to generate aerosol predominantly consisting of dispersed single fibers without changing their length and width is needed for inhalation studies. Here, we report a method (designated as Taquann method) to effectively remove the aggregate/agglomerates and enrich the well-dispersed singler fibers in dry state without dispersant and without changing the length and width distribution of the single fibers. This method is base on two major concept; liquid-phase fine filtration and critical point drying to avoid re-aggregation by surface tension. MWNT-7 was suspended in Tert-butyl alcohol, freeze-and-thawed, filtered by a vibrating 25 μm mesh Metallic Sieve, snap-frozen by liquid nitrogen, and vacuum-sublimated (an alternative method to carbon dioxide critical point drying). A newly designed direct injection system generated well-dispersed aerosol in an inhalation chamber. The lung of mice exposed to the aerosol contained single fibers with a length distribution similar to the original and the Taquann-treated sample. Taquann method utilizes inexpensive materials and equipments mostly found in common biological laboratories, and prepares dry powder ready to make well-dispersed aerosol. This method and the chamber with direct injection system would facilitate the inhalation toxicity studies more relevant to human exposure.

Pulmonary and pleural toxicity of potassium octatitanate fibers, rutile titanium dioxide nanoparticles, and MWCNT-7 in male Fischer 344 rats

“…All three particles were dispersed by the Taquann method to generate aerosols consisting predominantly of dispersed single fibers/particles (Taquahashi et al 2013). After dispersion, the material was stored in tert-butyl alcohol.…”

Involvement of IL-1 genes in the cellular responses to carbon nanotube exposure

“…This CNT has been shown to induce inflammatory responses in several in vitro and in vivo experiments [42,51,54,56]. The second CNT (designated as CNT-2) is a novel nanomaterial produced by the method of arc discharge by the Norwegian company n-Tec A/S and was kindly provided by Mr. Mogens Mathiesen.…”

Inhalation Exposure to Carbon Nanotubes (CNT) and Carbon Nanofibers (CNF): Methodology and Dosimetry

“…An improved dispersion method for aerosolizing MWCNT was developed by Taquahashi et al (2013) with the goal of generating predominantly single dispersed fibers by effectively removing agglomerates without changing length and diameter. Two preparatory steps were involved, starting with suspending MWCNT in tert -butyl alcohol (TB) followed by filtration through a vibrating metal sieve of 25 µm, then snap-freezing by liquid nitrogen and vacuum sublimination, which removed all TB.…”