Effects of Carbon-Based Nanomaterials on Human Cell Heath
Jennifer Jordan
The nanotechnology buzz cannot be ignored. Is all buzz good buzz? The advancement of carbon-based
nanomaterials (CBNs) is of high interest due to their wide range of applications such as, shrinking
electronics, strengthening materials, higher efficiency fuel cells, and advancing biomedicine [1, 2].
Although significant progress has been made in their maturity, little is known about the adverse effects
they may cause the human body. Specifically, the potential toxicity of carbon nanomaterials for medical
applications, cause a great deal of concern among those in the nanotechnology industry and eventually
the general public [2]. In the nanotechnology community, a big concern of medical uses for CNTs is their
structural resemblance to asbestos, which is linked to lung cancer [2-4].
In recent years, more and more studies are being conducted to determine just how safe carbon
nanomaterials really are. Arnaud Magrez and colleagues studied the toxicity of different types of
carbon-based nanomaterials with human cells [4]. In the study, Magrez and colleagues tested multi-wall
carbon nanotube (MWNT), carbon nanofibers (CNFs), and carbon nanoparticles (carbon black) in vitro
using lung tumor cells, H596, with varied dosage levels of 0.002, 0.02, and 0.2 g/mL. Results show the
toxicity was dependent on both the structures of the nanomaterials and the concentration. The larger
MWNTs were much less toxic than the smaller CNFs and carbon black at all concentrations over the 4
day culture [4]. Determination of living cells was correlated with the optical density, established by the
MTT assessment [6].
In another study by Guang et al. correlate CBN toxicity to their masses, rather than their physical size
[5]. Both studies show the dosage levels are indicative of the level of toxicity. Guang uses SWNTs,
MWNTs, quartz (control), and fullerenes (C60) with guinea pig lung alveolar macrophage (AM) as the cell
source. In this study, SWNTs were fabricated by electric arc discharge resulting 90% pure SWNTs with
cellular dosage range of 1.41-226.00 m/cm2 for SWNT and C60. The MWNTs were made by chemical
vapor deposition (CVD) yielding a 95% pure product, with dosages 1.41-22.60 m/cm2 [5]. These are
much higher and more tested dosages than the Magrez study. Also note the difference in cell medium
being used (lung cells from guinea pigs versus lung cells from human).
The smaller carbon black in [4] and SWNTs in [5] become toxic at lower dosage levels than the MWNT,
CNF, and carbon black [4], and MWNT, quartz, and C60 [5], respectively . However, the methodologies
are different and use different types of cells. Neither study used surfactants [5] or aggregating additives
[4] to keep the nanomaterials separated. This helps determine how in its true form carbon
nanomaterials may react in cells. The study used the widely accepted MTT reduction method assay [6].
After only 6 hours, the SWNT had a much higher toxicity level than MWNT, but both increased with
dosage level. The SWNTs, even at a low dose of 1.41 g/cm2, showed almost 20% toxicity. The toxicity
increases at a greater rate than that of MWNTs. At a dosage of 22.60 g/cm2, the MWNT toxicity
reaches about 14%, which is still notably lower than SWNT at a considerable lower dosage [5]. This
indicates cells are much more susceptible to the lighter SWNT than MWNT, which has a less surface
molecules exposed [2].
In both studies, the carbon-based nanomaterials all showed some level of toxicity to the lung cells. The
degree of which greatly depended on the type and dosage. Magrez inversely correlated the
nanomaterial size to its toxicity level, whereas Guang relates the toxicity to weight. Because the CNTs
had impurities of amorphous carbon and traces of other metals [5], it is very likely, that these impurities
and trace metals can increase toxicity in the cells [2]. Additionally the presence of “dangling bonds”
could impact toxicity in smaller nanomaterials, especially in an amorphous structure [4]. Additoinally,
both show definite signs of cellular change under a light microscope [4, 5].
These studies presented are focused on in vitro methods. How will the body react when carbon
nanomaterials invade in vivo? How much of a difference does the type of cell, and type of nonmaterial
(type of structure, material, size, surface area, and weight), play in its toxicity? At what point is a given
dosage of a particular nanomaterial considered to be an acceptable level? Although some studies, like
the ones discussed above, are being conducted to determine the likely cellular toxicity from carbonbased nanomaterials, research on the topic is still in its infancy. More research needs to be done to
determine if there is a real health hazard with CBNs. Even though carbon nanomaterials are very hopeful
for advancement in human health and several other areas of society, not much is known about the
potential side effects, in the human body, especially with long term exposure. Are the unknown risks
worth continuing development for the known benefits? Regardless, advancements in CBN will continue
to progress unless there is a strong case that they are detrimental to human health. Currently, the risks
are worth the rewards.
References:
1. C. M. Sayes, F. Liang, et al., “Functionalization Density Dependence of Single-Walled Carbon
Nanotubes Cytotoxicity in Vitro,” Toxicology Letters, August 2005.
2. A. Nel, T. Xia, L. Madler, N. Li, “Toxic Potential of Materials at the Nanolevel,” Science Magazine,
February 2003.
3. V. L. Colvin, “The Potential Environmental Impact of Engineered Nanomaterials,” Nature
Biotechnology, October 2003.
4. A. Magrez, S. Kasas, et al., “Cellular Toxicity of Carbon-Based Nanomaterials,” Nano Letters, May
2006.
5. J. Guang, H. Wang et al., “Cytotoxicity of Carbon Nanomaterials: Single-Wall Nanotube, MultiWall Nanotube, and Fullerene,” Environmental Science and Technology, January 2005.
6. T. Mosmann, “Rapid Colorimetric Assay for Cellular Growth and Survival: Application to
Proliferation and Cytotoxicity Assays, J. Immunol. Methods, 1983.