Early Combination of Material Characteristics and Toxicology Is Useful in the Design of Low Toxicity Carbon Nanofiber

Abstract

This paper describes an approach for the early combination of material characterization and toxicology testing in order to design carbon nanofiber (CNF) with low toxicity. The aim was to investigate how the adjustment of production parameters and purification procedures can result in a CNF product with low toxicity. Different CNF batches from a pilot plant were characterized with respect to physical properties (chemical composition, specific surface area, morphology, surface chemistry) as well as toxicity by in vitro and in vivo tests. A description of a test battery for both material characterization and toxicity is given. The results illustrate how the adjustment of production parameters and purification, thermal treatment in particular, influence the material characterization as well as the outcome of the toxic tests. The combination of the tests early during product development is a useful and efficient approach when aiming at designing CNF with low toxicity. Early quality and safety characterization, preferably in an iterative process, is expected to be efficient and promising for this purpose. The toxicity tests applied are preliminary tests of low cost and rapid execution. For further studies, effects such as lung inflammation, fibrosis and respiratory cancer are recommended for the more in-depth studies of the mature CNF product.

Carbon Nanofibers Have IgE Adjuvant Capacity but Are Less Potent Than Nanotubes in Promoting Allergic Airway Responses

“…Particle sample properties are shown in Table 1, while the methods used for particle characterization and more comprehensive characterization of the samples are previously reported [2, 7]. TEM micrographs at similar magnifications from CNF A, B, C, D, swCNT, and mwCNT samples are presented in Figures 1(a)–1(f), respectively.…”

“…An advantage of this study was the availability of four CNF batches manufactured in the same facility but with varying particle characteristics deliberately introduced by changing manufacturing conditions [7]. Despite their qualitative differences, the allergy-promoting capacity of the four CNF samples did not differ in the intranasal model, neither with regard to IgE levels nor eosinophil influx.…”

“…All particle samples were characterized by transmission electron microscopy (TEM), and the specific surface area was determined by nitrogen adsorption using the Brunauer, Emmet, and Teller method (BET). The endotoxin levels were determined in particle supernatants by the limulus amebocyte lysate (LAL) assay as previously described [2, 7], and the pH of the particle supernatants was measured (Mettler Toledo AS, NY, USA).…”

“…Carbon nanotubes (CNT) are particles applied in an increasing number of consumer products and are also incidental components in indoor air pollution [5, 6]. Carbon nanofibers (CNF) are useful in many of the same applications as CNT, such as Li-ion batteries and polymer nanocomposites [7]. In parallel to the increasing manufacture of CNT and CNF, there is a growing concern for the health impact of these nanoparticles in occupational workers and consumers in general, also in relation to allergy.…”

“…We, therefore, explored the importance of major physicochemical properties of carbon nanoparticles on their capacity to modulate allergy, by comparing the allergy-promoting capacity of samples having different physicochemical properties. Four samples of well-characterized, qualitatively different CNF produced in the same pilot plant were tested in both mouse models (CNF A, B, C, and D [7]). By deliberate use of different conditions and purification steps during the CNF manufacturing process, four samples with different particle properties such as fiber width and length, open versus closed channels, metal impurity content, relative surface area, presence of structural defects, and relative amount of fibers to other graphitic material were produced.…”