Biomolecular coronas in invertebrate species: Implications in the environmental impact of nanoparticles

The development of nanotechnology will inevitably lead to the release of consistent amounts of nanoparticles (NPs) in the environment. Invertebrates, that represent > 90% of animal species, widespread in different ecosystems, are emerging both as suitable target organisms and as models for evaluating the environmental impact of NPs. Once released in different ecosystems, both NP intrinsic properties and those of the receiving medium will affect particle behavior. In particular, interactions with different biomolecules will lead to the formation of ‘eco-coronas’, that will influence NP bioavailability/uptake/toxicity in different environments, depending on the organisms present and the surrounding conditions. However, as shown in mammalian studies, the evaluation of the biological effects of NPs requires additional understanding of how, once within the organism, NPs interact at the molecular level with cells in a physiological environment, i.e. in biological fluids. Different types of NPs associate with serum soluble components, organized into a ‘protein corona’, which confers a biological identity to NPs and affects their interactions with target cells. In comparison, the study on NP-protein coronas in invertebrates is still at its infancy, since the protein composition of their extracellular fluids is largely unknown, given the large diversity of phyla and species. From the first demonstration of an AgNP protein corona in the body fluid of earthworms, NP-protein coronas are being characterized in marine invertebrates. The identification of protein coronas formed with different types of NPs (amino modified polystyrene- PS NH2 and nano-oxides, n-CeO2 n-TiO2) in hemolymph serum of the marine bivalve Mytilus galloprovincialis is presented as a case study. The results indicate that, in Mytilus hemolymph, the formation of a biomolecular corona is partly NP-specific. The results obtained so far in terrestrial and marine invertebrates indicate that in each model, endowed with a peculiar protein repertoire, NP-coronas are characterized by unique protein components. The role of NP-protein coronas formed by lower organisms, and their possible contribution in evaluating the environmental impact of NPs are discussed.