From Basel: Biophysical Interactions at the Bio-nano Interface: Relevance for Aquatic Nanotoxicology
Ismael Rodea-Palomares, Universidad de Alcalá, Renata Behra and Laura Sigg, EAWAG
The intrinsic characteristics of nanomaterials imply a multi-variable complexity, which affects their toxicological potential. In many aspects, this complexity is related to their colloidal nature that distinguishes them radically from dissolved chemicals—whereas dissolved chemicals undergo chemical speciation, colloids are affected by both chemical and physical speciation. This fact has specific implications to their toxicological examination and their risk assessment, especially in aquatic systems.
Presentations in this session showed how toxicological properties of nanomaterials are studied by applying different novel approaches, including methods to untangle chemical effects (mediated by ions) and physical effects (nanoparticle-specific effects), methods to address and understand the issue of agglomeration and physical speciation and their implications for toxicity, and methods to untangle indirect effects (such as shading of algae by particle suspensions) from particle-specific and ion-mediated effects. An interesting approach included a change in perspective, studying the implications of biological traits of the organisms (e.g., size, aspect ratio, biovolume, etc.) in the toxicity of nanomaterials as a tool to perform effective interspecies extrapolations of nanomaterial bioactivity.
There were interesting lessons learned during the session. For example, in metal-based nanomaterials, free ion can be a determinant in the toxicity and may be behind some apparently “particle-specific effects.” Therefore, the contribution of free ion must always be under control. However, particle-specific effects were also evident even when the contribution of free ion was clearly determined. When speaking of particle-specific effects, internalization of nanoparticles seems not always required to induce toxicity. Therefore, it raises the question: Is internalization a prerequisite for particle-specific toxicity or is just surface adsorption enough? Many questions are still open with respect to internalization of nanoparticles: Why? How? When? In which organisms? A step forward from observation to understanding is required in this area. In addition, evidence presented showed that media composition and coatings may influence or even totally change the intrinsic toxicity of the nanomaterials. Therefore, further understanding of physical interactions and speciation of nanomaterials at the bio-interfaces is necessary, which may shed light on the definition of the “correct” conditions to properly perform and understand results from exposure experiments.
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