Page 417 - Environmental Nanotechnology Applications and Impacts of Nanomaterials

400 Potential Impacts of Nanomaterials

Figure 11.2 Transmission electron micrograph of a human epidermal keratinocyte
that was exposed to 0.4 mg/ml of the fullerene-based amino acid for 24 hours. Arrows
depict agglomerates in vacuoles around the periphery of the nucleus.

periphery of the nucleus in large vacuoles (Figure 11.2). Human epi-
dermal keratinocytes exposed to fullerene-based amino acid solu-
tions ranging from 0.04–0.004 mg/ml resulted in a significant
decrease in viability and a statistically significant increase in IL-8
at a dose of 0.04 mg/ml over periods of 8, 12, and 24 hours. IL-6 and
IL-1β were greater at 24 and 48 hours, but there was no significant
TNF-α or IL-10 expression. (Rouse et al., 2006).
Studies were also conducted with a fullerene-substituted phenylala-
nine derivative of a nuclear localization peptide sequence to evaluate the
effects on mechanical stressors such as repetitive flexing motion. Skin
flexed for 60 or 90 minutes and dosed with the fullerene or left unflexed
(control) was studied by confocal laser microscopy which depicted pen-
etration after 60 and 90 minutes of flexion and 8 hours of flow-through
diffusion and further penetration after 24 hours of flow-through diffu-
sion. This study showed that mechanical flexion caused an increase in
nanoparticle penetration through skin (Rouse et al., 2007).
In contrast with these studies suggesting toxicity of various fullerenes
and their derivatives, other studies have concluded that fullerenes
may have beneficial effects for cells. Numerous studies have also been
published that show functionalized fullerenes to be therapeutically
useful in the treatment of a number of diseases. A balanced benefit-
risk assessment must be made before these substances are released for
human use.