79
TiO 2 nanoparticles played a role in toxicity, the larger being safer than smaller, with
a value of LC50(120 hpf) = 23.4 μg/ml for nanoparticles sized 6 nm (Kim et al.
2014). The shape of nanoparticles, instead, did not play a major role: embryos were
safely exposed to spheres and plates, and only bipyramidal nanoparticles induced
some increase of malformation, no more than 20% at the highest concentration used
(van Pomeren et al. 2017b). The titanium dioxide nanoparticles were safe at
concentration as high as 1000 μg/ml, also in another alternative model organism, the
amphibian, Xenopus laevis (Nations et al. 2011). The most important characteristic
of titanium dioxide is its photo-activity: under direct sunlight or UV irradiation, the
production of reactive oxygen species greatly increases, with dramatic changes of
embryotoxicity. The yolk-sac larvae were the most sensitive stage to the phototoxicity
of titanium dioxide nanoparticles, while embryos, free-swimming larvae, and
juvenile were resistant (Ma and Diamond 2013). The effect of UV irradiation
enhanced the malformation rate of plate-shaped nanoparticles (ID50 = 0.015 μg/
ml), and that of spheres and bipyramids remained unchanged. The mortality rate
under irradiation was increased in all differently shaped nanoparticles; however,
LC50 was never reached (van Pomeren et al. 2017b). The weak or absent toxicity
observed in zebrafish embryonic test with photo-inactivated TiO2 nanoparticles
doped in sulfur- or sulfur and fluorine is a countercheck of the fundamental role of
irradiation (Pathakoti et al. 2013). As a general remark, the titanium dioxide
nanoparticles are weak embryotoxic in itself, but can represent a threat for many
species under sunlight or UV irradiation.
The zinc oxide nanoparticles are also widely diffused. Their toxicity included
reduced hatching and increased heart rate, possibly due to hypoxia, in zebrafish
embryos exposed to 10–120 μg/ml. The toxic mechanisms included the oxidative
stress and apoptosis, with reduced potential of the mitochondrial membrane and
altered expression of genes related to both processes (Zhao et al. 2016). The embryo
toxicity of zinc oxide nanoparticles increased the theratogenicity of an environmental
pollutant, the perfluorooctane sulfonate (Du et al. 2016). However, the mortality
rate and the prevalence of sever malformations after exposure to zinc oxide were not
reported in zebrafish embryonic test. The results obtained in Xenopus laevis, in
which ID50 (96 h) = 10.3 μg/ml and 89% of gut malformation were recorded
(Nations et al. 2011), suggest species-specific sensitivity to these nanoparticles.
Attempts to reduce the dissolution from nanoparticles included doping in silver,
which reduced the hatching failure. The engineered nanoparticles of zinc oxide in a
shell of gadolinium oxide were intended as a probe for imaging. They anticipated
the hatching at 72 hpf, but induced multiple malformations, dose-dependent in
incidence and severity (Woźniak et al. 2017).
Other metal- and metal oxide-based nanoparticles have been tested with the
zebrafish embryonic test. Copper-based nanoparticles were weakly toxic, with
LC50 greater than 1000 μg/ml in standard medium and after 96 hour of exposure
(Nations et al. 2011), and over 100 μg/ml in natural freshwater (Heinlaan et al.
2016). Another study reported lower values, LC50 = 10 μM and ID50 = 0.5 μM for
delayed hatching (Thit et al. 2017). The effect of nanoparticles and ions were
comparable, the dissolution low. Copper nanoparticles seemed to be more toxic to
3 Safety and Utility of Nanomaterials on Reproduction and Development: An Update…
TiO 2 nanoparticles played a role in toxicity, the larger being safer than smaller, with
a value of LC50(120 hpf) = 23.4 μg/ml for nanoparticles sized 6 nm (Kim et al.
2014). The shape of nanoparticles, instead, did not play a major role: embryos were
safely exposed to spheres and plates, and only bipyramidal nanoparticles induced
some increase of malformation, no more than 20% at the highest concentration used
(van Pomeren et al. 2017b). The titanium dioxide nanoparticles were safe at
concentration as high as 1000 μg/ml, also in another alternative model organism, the
amphibian, Xenopus laevis (Nations et al. 2011). The most important characteristic
of titanium dioxide is its photo-activity: under direct sunlight or UV irradiation, the
production of reactive oxygen species greatly increases, with dramatic changes of
embryotoxicity. The yolk-sac larvae were the most sensitive stage to the phototoxicity
of titanium dioxide nanoparticles, while embryos, free-swimming larvae, and
juvenile were resistant (Ma and Diamond 2013). The effect of UV irradiation
enhanced the malformation rate of plate-shaped nanoparticles (ID50 = 0.015 μg/
ml), and that of spheres and bipyramids remained unchanged. The mortality rate
under irradiation was increased in all differently shaped nanoparticles; however,
LC50 was never reached (van Pomeren et al. 2017b). The weak or absent toxicity
observed in zebrafish embryonic test with photo-inactivated TiO2 nanoparticles
doped in sulfur- or sulfur and fluorine is a countercheck of the fundamental role of
irradiation (Pathakoti et al. 2013). As a general remark, the titanium dioxide
nanoparticles are weak embryotoxic in itself, but can represent a threat for many
species under sunlight or UV irradiation.
The zinc oxide nanoparticles are also widely diffused. Their toxicity included
reduced hatching and increased heart rate, possibly due to hypoxia, in zebrafish
embryos exposed to 10–120 μg/ml. The toxic mechanisms included the oxidative
stress and apoptosis, with reduced potential of the mitochondrial membrane and
altered expression of genes related to both processes (Zhao et al. 2016). The embryo
toxicity of zinc oxide nanoparticles increased the theratogenicity of an environmental
pollutant, the perfluorooctane sulfonate (Du et al. 2016). However, the mortality
rate and the prevalence of sever malformations after exposure to zinc oxide were not
reported in zebrafish embryonic test. The results obtained in Xenopus laevis, in
which ID50 (96 h) = 10.3 μg/ml and 89% of gut malformation were recorded
(Nations et al. 2011), suggest species-specific sensitivity to these nanoparticles.
Attempts to reduce the dissolution from nanoparticles included doping in silver,
which reduced the hatching failure. The engineered nanoparticles of zinc oxide in a
shell of gadolinium oxide were intended as a probe for imaging. They anticipated
the hatching at 72 hpf, but induced multiple malformations, dose-dependent in
incidence and severity (Woźniak et al. 2017).
Other metal- and metal oxide-based nanoparticles have been tested with the
zebrafish embryonic test. Copper-based nanoparticles were weakly toxic, with
LC50 greater than 1000 μg/ml in standard medium and after 96 hour of exposure
(Nations et al. 2011), and over 100 μg/ml in natural freshwater (Heinlaan et al.
2016). Another study reported lower values, LC50 = 10 μM and ID50 = 0.5 μM for
delayed hatching (Thit et al. 2017). The effect of nanoparticles and ions were
comparable, the dissolution low. Copper nanoparticles seemed to be more toxic to
3 Safety and Utility of Nanomaterials on Reproduction and Development: An Update…