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conditions improved the tolerance of E. coli to toxicants. According to the
authors, the effect of water chemistry on the physicochemical properties of
nanoparticles should receive more attention in future nanotoxicity evaluations.
Bai et al. ( 2010 ), in turn, evaluated the ZnO nanoparticle (nano-ZnO, 30 nm)
properties in a water suspension (E3 medium) and then used a zebrafish 96-h post
fertilization embryo-larval test to assess the toxicity of nano-ZnO suspension. As in
the other studies, nano-ZnO was found to readily form aggregates with different
sizes: small aggregates (142.4-517.7 nm) were suspended in E3 medium, but large
aggregates ( > 1 μ m) quickly deposited on the bottom of 24-well plates; nano-ZnO
was partially dissolved to Zn species. The embryo toxicity test revealed that nano-
ZnO killed zebrafish embryos (50 and 100 mg L 1 ), retarded the embryo hatching
(1-25 mg L 1 ), reduced the body length of larvae, and caused tail malformation
after the 96 h of exposure. The dissolved zinc only partially contributed to the
toxicity of nano-ZnO.
13.5.3 Barium Titanate (BaTiO 3 )
Barium titanate (BaTiO 3 , BT) is a perovskite-like oxide traditionally known to be
an important semiconductor/ferroelectric material with remarkable dielectric con-
stant and therefore with high employability in the electroceramics field (Ciofani
et al. 2010a ). Nanosized barium titanate (BT), in turn, has been recently gaining
application in biomedicine, as a biological nanocarrier for proteins (Ciofani
et al. 2010a ), an uptake enhancer of low-molecular-weight drugs such as doxoru-
bicin (Ciofani et al. 2010b ), a biomarker for imaging probes (Hsieh et al. 2010 ), and
as bone graft material (Ball et al. 2014 ).
Polonini et al. ( 2014 ) performed ecotoxicological tests on three aquatic micro-
organisms: C. vulgaris , A. flos - aquae , and E. gracilis . Two materials (micro- and
nanosized) were used. They were identified by XRD as tetragonal BaTiO 3 (BT MP)
and cubic BaTiO 3 (BT NP), with average crystallite sizes of 172.0
102.4
Å
(with
0.19
0.05 %), respectively.
Using SEM and TEM, the diameter of the particles could be estimated as 170 nm
(BT MP) and 60 nm (BT NP), and the BT MP presented some degree of
polydispersion. The BET surface area was calculated as 3.24 m 2 g 1 for BT MP
and 16.60 m 2 g 1 for BT NP; the total pore volumes were 0.006 and 0.07 cm 3 g 1 ,
respectively, and the mean pore diameters were 7.34 and 17.46 nm, respectively.
Both materials were negative and easily aggregated (unstable) in all aqueous media
studied, and the release rate of Ba 2+ ions did not exceed 1.5 %. BT presented a
statistically significant toxic effect on C. vulgaris growth from the lowest concen-
tration tested (1 μ gmL 1 ) that seemed to be mediated by an induced oxidative
stress. For A. flos - aquae , BT had a low toxic effect on the growth, but both particles
affected cell viability from the lowest concentration tested, which was caused by
indirect effect on oxidative stress in cells. For E. gracilis , BT showed a statistically
0.06 % of micro strain) and 60.0
16.7
Å
(0.10
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