Reducing the Toxicity of Carbon Nanotubes and Fullerenes Using Surface Modifi cation Strategy - Management of Natural Resources in a Changing Environment - page 182

Table 5 (continued)

Type of fullerene Study/test Result References

Pure fullerene suspension
and water-soluble
polyhydroxylated
fullerene [C60(OH)n]

The mechanisms
underlying the
cytotoxic action.
Crystal violet assay
for cell viability

Pure fullerene was at least
three orders of magnitude
more toxic than C60(OH)n
to mouse L929
fi brosarcoma, rat C6
glioma, and U251 human
glioma cell lines.

Isakovic
et al. ( 2006 )

LC50 of C60: 0.25 ʼ g/ml;

LC50 of C60(OH)n:
800-1,000 ʼ g/ml

C60, C70 and C60(OH)24 Embryonic zebrafi sh

morphological and
cellular responses

Exposure to 200 lg/L C60
and C70 induced a
signifi cant increase in
malformations, pericardial
edema, and mortality;
while the response to
C60(OH)24 exposure
was less pronounced at
concentrations an order
of magnitude higher.
Exposure to C60 induced
both necrotic and apoptotic
cellular death throughout
the embryo.

Crystal
et al. ( 2007 )

C82(OH)22, C60(OH)22,
C60(C(COOH)2)2

H2O2-induced
oxidative injury
within A549 lung
epithelial and rat
brain capillary
endothelial cells

Protective effects of
fullerenes are dependent
on ability to scavenge
ROS, which is increased
by greater derivatization

Yin et al.
( 2009 )

Non-treated C60,
SWCNTs and MWCNTs

Macrophages Cytotoxicity of C60

was lower than that of
SWCNTs and MWCNTs

Jia et al.
( 2005 )

Conclusions

This study identifi ed the CNT/fullerene and its derivatives with lesser risks for given
sets of required properties by exploring and analyzing the toxicity studies reported till
date in published reports and literature. From number of toxicity studies of non-
derivatized and derivatized fullerene it can be concluded that as the number of
hydroxyl or carboxyl groups on the surface of the fullerene cage increases, cytotox-
icity decreases. For non-derivatized fullerenes, generally organic solvents are used
during the specimen treatment process to make it soluble in water and the residual
organic solvents are capable of contributing toxicity. In case of CNTs it is reported
that toxicity can be reduced by keeping their length less than 5 ʼ m. CNT became