Cytoprotective Activities of Water-Soluble Fullerenes in Zebrafish Models - Zebrafish: Methods for Assessing Drug Safety and Toxicity - page 250

fullerene and reactive oxygen species. The concentrations required for effective
biological protection in mammalian cell cultures appear to be in the 10-100 M

range (Yamago et al., 1995; Dugan et al., 1996, 1997, 2001; Huang et al., 1998,
2001a; Lotharius et al., 1999; Fumelli et al., 2000; Lin et al., 2004). Data using
antibodies against fullerenes indicate that water-soluble fullerenes readily
enter many cell types, and may be located preferentially with mitochondria (Foley
et al., 2002), although it is not clear whether they can enter the mitochondria to any
significant extent.
One of the leading candidates for a pharmacologically active formof fullerenes is
the e,e,e-trismalonic acid (1) (so-called C3) (Fig. 19.1). C3 (1) has been shown to
protect against oxidative injury and cell death in a variety of cell culture and animal
models (Dugan et al., 1996, 1997, 2001; Djojo and Hirsch, 1998; Straface et al., 1999;
Bisaglia et al., 2000; Fumelli et al., 2000; Lin et al., 2000; Monti et al., 2000; Foley
et al., 2002; Reuther et al., 2002; Ali et al., 2004). Moreover, C3 fullerenes appear to
cross the blood-brain barrier in detectable amounts and are eliminated almost entirely
from the body via the liver and kidneys.
We have recently synthesized and characterized various new families of water-
soluble fullerenes that can be prepared in scalable amounts and have compared their
activities against C3 (1) (Witte et al., 2007). We observed broad differences among the
various modified fullerenes with respect to both superoxide quenching and interaction
with cytochrome c. One factor linked to the overall antioxidant capabilities was net
charge of the modified fullerene. Anionic fullerenes give rise to stronger binding of
cytochrome c. On the other hand, monoadducts (e.g., dendrofullerenes 2-7)tendtohave
enhanced activity of superoxide quenching compared with higher adducts such as C3-
like fullerenes (1 and 8-10)oroxo-aminofullerenes11 and 12 (Fig. 19.1 and Table 19.1)
(Witte et al., 2007). However, other, as yet unknown, factors appear to play a role as well.
We have extended our observations on the cytoprotective antioxidant effects of a
subset of our water-soluble fullerenes 1-12 (Fig. 19.1) to zebrafish (Danio rerio), a

m

Table 19.1 IC 50 Values for the Superoxide Quenching Activities of Fullerene Derivatives
1-12 in Xanthine/Xanthine Oxidase Assays

Compound Class IC 50 superoxide (mM)

1 C3-like fullerenes 18.5

2 Dendrofullerenes 6.2

3 Dendrofullerenes 11.0

4 Dendrofullerenes 15.4

5 Dendrofullerenes 14.7

6 Dendrofullerenes 24.0

7 Dendrofullerenes 26.1

8 C3-like fullerenes 56.0

9 C3-like fullerenes 35.0

10 C3-like fullerenes 202.0

11 Oxo-aminofullerenes 35.0

12 Oxo-aminofullerenes 45.4