Embryotoxic potential of engineered nanoparticles: Lessons from mammalian and non-mammalian species

Engineered nanomaterials (ENM) are a new class of purposefully produced particles sharing the property of having at least one dimension lower than 100 nm. This fact seems to confer them new characteristics in comparison to the bulk form and/or to emphasize some intrinsic properties of the material. These characteristics are relevant for industry and bio-medicine, but may lead to enhanced toxicity in humans. There is in fact suggestion that some peculiar physico-chemical properties of ENM may be linked to specific adverse effects. Very recently, data are being accumulated about possible toxic effects on embryo survival and development after exposure during pregnancy, a situation with relevant social and clinical implication. In this review, we critically analyze the most relevant studies on this subject, placing emphasis to chemical and physical properties associated with their effect. In detail, we examined whether the embryotoxic effect of ENM of similar size and shape may vary according to their different chemical composition, and whether, within the same class of ENM (e.g. carbon nanotubes) toxicity may be modulated by the presence of different contaminants retained during the synthetic process, by the introduction of different chemical groups (functionalization), generally aimed to improve their solubility for biomedical utilization, or by strong acidic treatments often used to remove impurities. The different embryotoxic effect due to changes in size and shape of ENM of the same chemical composition has been also reported.