Environmental Engineering Reference
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Mechanistic explanation has also been given in a study supporting the reduced acute
toxicity of functionalized fullerenes. The differential cytotoxicity of a series of
water-soluble fullerene species showed that changes in the fullerene cage structure
had substantial impact on in vitro cytotoxicity. As the number of hydroxyl or
carboxyl groups on the surface of the fullerene cage was increased, cytotoxicity
decreased over seven orders of magnitude. In a study (Chen et al.
1998
), polyalkyl-
sulfonated fullerenes (in water) were not found to be lethal, subsequent to the oral
exposure of rats in acute (50 mg/kg, single administration) or subacute (50 mg/kg
daily for 12 days) exposure setups, and as a consequence was considered to be nontoxic.
It should be noted that fullerol have proved to be less cytotoxic than fullerene in the
in vitro fi broblast test system. Fullerol at 50 mg/L (Zhu et al.
2007
) did not exert
toxicity to zebrafi sh embryos. In contrast, nC60 at 1.5 mg/L delayed zebrafi sh
embryo and larval development, decreased survival and hatching rates, and caused
pericardial edema. However, tetrahydrofuran treated C60, C60(OH)18 generated
cytotoxicity which was related to the residual THF. It was reported that tetrahydro-
furan used for the purifi cation and dispersion of C60 remained in C60 aggregates
after the treatment and enhanced the cytotoxicity. THF-pre-treated C60 induced
mortality in fathead minnows, whereas stirring of engineering nanoparticles in
water did not affect survival. However, lipid peroxidation was observed in the gill.
One of the publications linked the toxic effects directly to a THF degradation product
(
-butyrolactone) rather than to C60 and may explain toxicity attributed to C60 in
other investigations (Kovochich et al.
2009
). The selected toxicity results have been
compared and summarized in Table
5
.
ʳ
Table 5
Selected toxicity comparison studies of modifi ed/unmodifi ed fullerenes
Type of fullerene
Study/test
Result
References
Fullerene, Substituted
fullerene
In vitro Cytotoxicity
The unsubstituted fullerene
exhibited the highest
toxicity whereas more
functionalised (and polar)
derivatives showed
decreased toxicity.
Sayes et al.
(
2004
)
Fullerenols
Human epidermal
keratinocytes
Hydroxylation of
fullerenes caused no
cytotoxicity or
infl ammation up
to 8.55
Saathoff
et al. (
2011
)
ʼ
g/ml.
Functionalised fullerenes,
CD-C60, hexa-C60,
and tris-C60
Cytokine secretion
profi le of dermal
epithelial cells.
tris-C60 signifi cantly
reduces infl ammatory
cytokine release in a
dose- and time-dependent
manner; CD-C60
demonstrated a relatively
pro-infl ammatory cytokine
response, while hexa-C60
did not signifi cantly
perturb cytokine responses
Gao et al.
(
2010
)
(continued)
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