The key focus of future nano-impact studies should be marine nano-ecotoxicology. Several important issues need to be highlighted and discussed, as follows
1 - Proper and ad hoc ecotoxicological approach
A classical ecotoxicological approach based on controlling sources, as well as uses of chemicals, may be not always possible for nanomaterials. Pathways between release and targets should be evaluated, considering that they are mainly influenced by transport and transformation which could both occur in the natural environment. Transport processes largely leave the structure and properties unchanged. Transformation and bioavailability strongly depend on the local chemistry of the environment. Transformation includes physical, chemical, photochemical reactions, as well as biological reactions within or in the presence of organisms. A well designed and comprehensive risk-oriented ecotoxicological study in the marine environment should address the following issues:
1) diversity and variability, including characterization and functionalization;
2) transformations, in terms of chemical and biological processes occurring in the full life-cycle;
3) the “Trojan horse” effect for other marine chemicals, including pollutants which can affect bioavailability, uptake, bioaccumulation, trophic web transfer and toxicity;
2 - Specific area of research
An area on which ecotoxicological approaches should focus is addressing the chemical or biological transformation of nanomaterials and their ultimate impact on targets and the environment. While some types of nanomaterials may be toxic in the laboratory and inert in the natural environment, it is also possible that other types may become more biologically available and toxic as a result of abiotic and biotic transformations in a complex ecosystem such as the marine environment;
3 - Biological Models
Different marine biological models could be used, from primary cell cultures to whole animals/plants, from in vitro to in vivo studies using standard and, more importantly, innovative bioassays.
4 - Toxicity
Endpoints of toxicity both classical and recently developed need to be investigated with various biological targets from cell surface defence mechanism (ABC transporters) to biotransformation, oxidative stress, genotoxicity, immunotoxicity and organ/function impairment. Important connections with human immunology is mandatory in order to be evaluated alternative methods to current in vivo immunological assays. For example, the immune system of the sea urchin, the only marine invertebrate whose genome has been fully sequenced so far (Science 2006), has been found complex and very sophisticated, with an astonishing large repertoire of innate pathogen recognition proteins. Thus, given their phylogenetically close relationship, the comparative analysis of the effects of NPs on the sea urchin immune system, will have broad implications for understanding the evolution of host defenses and genetic underpinning of immunity in vertebrates. Genomes and/or other “omic” tools, now accessible as global expression analysis, as predictive markers, validated and anchored to functional assays, should be considered. Micro- and meso-cosms should be considered, in order to perform fate and transport studies by modifying external environmental factors in different experimental approaches and determining those relevant in realistic environmental conditions.
5 - Resources and competencies database
Build up a web-based data repository for any experimental purpose concerning marine organisms exposure based on the current difficulties in setting up specific protocols and procedures for both in vitro and in vivo studies with ENM in sea waters.