Biological response and developmental toxicity of zebrafish embryo and larvae exposed to multi-walled carbon nanotubes with different dimension.

The development and use of nanomaterials are increasing significantly. Among nanomaterials, carbon nanotubes are of particular interest due to its distinctive physicochemical properties. This material composed of sheets of graphite has very high thermal conductivity, metallic-type electrical conductivity, stiffness, toughness and unique ability to bond to itself in an extended network with extraordinary strength. Its application in the industry is continuously growing, which could lead to the accumulation in the environment and a consequent impact on both humans and ecosystems. Considering that environmental systems are dynamic, it is difficult to predict the risks associated with the release of nanomaterials to the environment. Bioindicators are useful tools as primary signals of environmental risk, and their responses reveal the organism and ecosystem health. In the present study, we evaluated the impact of multi-walled carbon nanotubes with different dimensions and agglomeration pattern on zebrafish embryo and larvae; mainly, studies were focused on physiological and behavioral responses. In embryos, measurements were hatching rate, morphology changes, and viability. In larvae, locomotor activity, heart rate, innate inflammatory response, general and tissue-specific morphology were measured. MWCNT-S (short, wide and mostly dispersed) caused depression of the locomotor activity of larvae, indicating an alteration of the central nervous system, and depression of neutrophil migration activity. MWCNT-L (long, thin and agglomerated) caused malformations during larval development, a decrease of neutrophil migration and alteration of cardiac rhythm. Results obtained for both carbon nanotubes were different, highlighting the importance of dimensions of the same nanomaterial, and also the kind of agglomeration and shape adopted, for the toxic effects on organisms.

In vivo study of teratogenic and anticonvulsant effects of antiepileptics drugs in zebrafish embryo and larvae.

Epilepsy is a neurological disorder treated with antiepileptic drugs (AEDs). Since AEDs are administered in women in childbearing age, it is critical to study if drugs are capable of inducing developmental toxicity. Along the bibliography available, there is no research comparing teratogenicity and anticonvulsant effect within the same study. In the present study, we evaluated the teratogenic and anticonvulsant effects of six different AEDs: carbamazepine, levetiracetam, lamotrigine, phenobarbital, phenytoin and valproic acid. Zebrafish was the selected animal model because of its small size, rapid external development and similar neurophysiology to mammals. Zebrafish embryo and larvae were exposed to AEDs. Embryo development was monitored by their hatching and morphology. In larvae, locomotor activity was measured as a parameter of neurotoxicity. Finally, anticonvulsant effect was determined after exposure to AEDs in zebrafish larvae treated with the proconvulsant drug pentylenetetrazole. Our results suggest that lamotrigine and phenytoin could be suitable non-teratogenic and efficient anticonvulsant options for epilepsy treatment.

Relation between biophysical properties of nanostructures and their toxicity on zebrafish.

In recent years, the use of commercial nanoparticles in different industry and health fields has increased exponentially. However, the uncontrolled application of nanoparticles might present a potential risk to the environment and health. Toxicity of these nanoparticles is usually evaluated by a fast screening assay in zebrafish (Danio rerio). The use of this vertebrate animal model has grown due to its small size, great adaptability, high fertilization rate and fast external development of transparent embryos. In this review, we describe the toxicity of different micro- and nanoparticles (carbon nanotubes, dendrimers, emulsions, liposomes, metal nanoparticles, and solid lipid nanoparticles) associated to their biophysical properties using this model. The main biophysical properties studied are size, charge and surface potential due to their impact on the environment and health effects. The review also discusses the correlation of the effects of the different nanoparticles on zebrafish. Special focus is made on morphological abnormalities, altered development and abnormal behavior. The last part of the review debates changes that should be made in future directions in order to improve the use of the zebrafish model to assess nanotoxicity.