188
(anatase and a mixture of anatase 80% and rutile 20%) were evaluated at the same
light conditions. The occurrence of sublethal effects was influenced not only by
illumination condition but also by titanium dioxide nanoparticle crystal phase. Pure
anatase produced more oxidative damage without co-exposure to UV, while the
mixture anatase:rutile caused more sublethal effects under UV (Clemente et al.
2015). Light conditions also play an important role in the dissolution processes of
nanoparticles as silver nanoparticles and zinc oxide nanoparticles (Odzak et al. 2017).
Given the possibility of long-term exposure of nanomaterials, it becomes important to apply a set of bioassays in the evaluation of the potential hazard taking into
account these factors. For this purpose, bioassays as survival rates, malformation,
size, hatching, and biochemical biomarkers may be performed in different organisms exposed in different experimental conditions (Bour et al. 2015).
Zebrafish (Danio rerio) embryos are one of the most common in vivo model
systems for high-throughput toxicity screening of chemicals because of their small
size, rapid development, and high fecundity (Felix et al. 2016). Therefore, it is considered an excellent model for ecotoxicological (Pecoraro et al. 2018) molecular
studies, embryonic development, and developmental biology (Brohi et al. 2017).
Zebrafish embryo toxicity test has been shown to have results that correlate well
with those of adult fish acute toxicity tests (Lammer et al. 2009; Belanger et al.
2013; Scholz et al. 2013; Busquet et al. 2014). Moreover, zebrafish embryo assays
are pain-free in vivo tests, and embryonic development is perceptive to environment
stress (Mu et al. 2016). In relation to titanium dioxide nanoparticle effects on zebrafish, the exposure to titanium dioxide nanoparticles anatase (TA) or an anatase/rutile
mixture (TM) under UV irradiation accelerated hatching of the larvae and may have
altered the equilibrium of the larvae and caused some oxidative stress. Under UV
irradiation, greater mortality of the larvae of the groups exposed to TM was observed
compared to TA (Clemente et al. 2014b).
Factors such as pH, ionic strength, and sunlight can interfere in the degree of
toxicity and effects resulting from a combination of them are dynamic and complex.
Another environmental factor that can alter nanoparticle toxicity is natural organic
matter (NOM) presence. The stabilization of nanoparticles in aquatic systems due
to NOM may be of concern due to their mobility. Different aquatic sources of NOM
can result in variance of toxicity, and different concentrations of humic acid (HA)
can affect aggregation and toxicity (Ong et al. 2017).
Recently, Clemente et al. (2017) showed that the presence of NOM changed
graphene oxide toxic effects on aquatic organisms. They evaluated the toxicological
effects of graphene oxide through tests with Danio rerio embryos, considering the
washing treatment and the interaction with organic matter. Although the embryo
exposure showed no acute toxicity or malformation, the larvae exposed to graphene
oxide presented a reduction in the length and acetylcholinesterase activity. The
authors observed that although there is a critical influence of oxidative debris (OD)
on the graphene oxide material biological reactivity and hydroxyapatite interaction,
the findings indicate a mitigation of material toxicity after OD removal.
Nanohybrid materials are emerging nanosystems where the properties that command the toxicity may be different compared to the isolated materials. Therefore,
F. F. Pereira et al.
(anatase and a mixture of anatase 80% and rutile 20%) were evaluated at the same
light conditions. The occurrence of sublethal effects was influenced not only by
illumination condition but also by titanium dioxide nanoparticle crystal phase. Pure
anatase produced more oxidative damage without co-exposure to UV, while the
mixture anatase:rutile caused more sublethal effects under UV (Clemente et al.
2015). Light conditions also play an important role in the dissolution processes of
nanoparticles as silver nanoparticles and zinc oxide nanoparticles (Odzak et al. 2017).
Given the possibility of long-term exposure of nanomaterials, it becomes important to apply a set of bioassays in the evaluation of the potential hazard taking into
account these factors. For this purpose, bioassays as survival rates, malformation,
size, hatching, and biochemical biomarkers may be performed in different organisms exposed in different experimental conditions (Bour et al. 2015).
Zebrafish (Danio rerio) embryos are one of the most common in vivo model
systems for high-throughput toxicity screening of chemicals because of their small
size, rapid development, and high fecundity (Felix et al. 2016). Therefore, it is considered an excellent model for ecotoxicological (Pecoraro et al. 2018) molecular
studies, embryonic development, and developmental biology (Brohi et al. 2017).
Zebrafish embryo toxicity test has been shown to have results that correlate well
with those of adult fish acute toxicity tests (Lammer et al. 2009; Belanger et al.
2013; Scholz et al. 2013; Busquet et al. 2014). Moreover, zebrafish embryo assays
are pain-free in vivo tests, and embryonic development is perceptive to environment
stress (Mu et al. 2016). In relation to titanium dioxide nanoparticle effects on zebrafish, the exposure to titanium dioxide nanoparticles anatase (TA) or an anatase/rutile
mixture (TM) under UV irradiation accelerated hatching of the larvae and may have
altered the equilibrium of the larvae and caused some oxidative stress. Under UV
irradiation, greater mortality of the larvae of the groups exposed to TM was observed
compared to TA (Clemente et al. 2014b).
Factors such as pH, ionic strength, and sunlight can interfere in the degree of
toxicity and effects resulting from a combination of them are dynamic and complex.
Another environmental factor that can alter nanoparticle toxicity is natural organic
matter (NOM) presence. The stabilization of nanoparticles in aquatic systems due
to NOM may be of concern due to their mobility. Different aquatic sources of NOM
can result in variance of toxicity, and different concentrations of humic acid (HA)
can affect aggregation and toxicity (Ong et al. 2017).
Recently, Clemente et al. (2017) showed that the presence of NOM changed
graphene oxide toxic effects on aquatic organisms. They evaluated the toxicological
effects of graphene oxide through tests with Danio rerio embryos, considering the
washing treatment and the interaction with organic matter. Although the embryo
exposure showed no acute toxicity or malformation, the larvae exposed to graphene
oxide presented a reduction in the length and acetylcholinesterase activity. The
authors observed that although there is a critical influence of oxidative debris (OD)
on the graphene oxide material biological reactivity and hydroxyapatite interaction,
the findings indicate a mitigation of material toxicity after OD removal.
Nanohybrid materials are emerging nanosystems where the properties that command the toxicity may be different compared to the isolated materials. Therefore,
F. F. Pereira et al.