We demonstrate that it is possible to identify the protein--nanoparticle interaction site at amino acid scale in solution. Using NMR, chemical shift perturbation analysis, and dynamic light scattering we have identified a specific domain of human ubiquitin that interacts with gold nanoparticles. This method allows a detailed structural analysis of proteins absorbed onto surfaces of nanoparticles in physiological conditions and it will provide much needed experimental data for better modeling and prediction of protein--nanoparticle interactions.

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Nanotechnology is an emerging field that involves the development, manufacture and measurement of materials and systems in the submicron to nanometer range. Its development is expected to have a large socio-economical impact in practically all fields of industrial activity. However, there is still a lack of information about the potential risks of manufactured nanoparticles for the environment and for human health. In this work, we studied the cytotoxicity, genotoxicity and morphological transforming activity of cobalt nanoparticles (Co-nano) and cobalt ions (Co(2+)) in Balb/3T3 cells. We also evaluated Co-nano dissolution in culture medium and cellular uptake of both Co-nano and Co(2+). Our results indicated dose-dependent cytotoxicity, assessed by colony-forming efficiency test, for both compounds. The toxicity was higher for Co-nano than for Co(2) after 2 and 24 h of exposure, while dose-effect relationships were overlapping after 72 h. Statistically significant results were observed for Co-nano with the micronucleus test and the comet assay, while for Co(2+) positive results were observed only with the latter. In addition, even when Co-nano was genotoxic (at >1 microM), no evident dose-dependent effect was observed. Concerning morphological transformation, we found a statistically significant increase in the formation of type III foci (morphologically transformed colonies) only for Co-nano. Furthermore, we observed a higher cellular uptake of Co-nano compared with Co(2+).

Despite human gastrointestinal exposure to nanoparticles (NPs), data on NPs toxicity in intestinal cells are quite scanty. In this study we evaluated the toxicity induced by zinc oxide (ZnO) and titanium dioxide (TiO₂) NPs on Caco-2 cells. Only ZnO NPs produced significant cytotoxicity, evaluated by two different assays. The presence of foetal calf serum in culture medium significantly reduced ZnO NPs toxicity as well as ion leakage and NP-cell interaction. The two NPs increased the intracellular amount of reactive oxygen species (ROS) after 6 h treatment. However, only ZnO NPs increased ROS and induced IL-8 release both after 6 and 24 h. Experimental data indicate a main role of chemical composition and solubility in ZnO NPs toxicity. Moreover our results suggest a key role of oxidative stress in ZnO NPs cytotoxicity induction related both to ion leakage and to cell interaction with NPs in serum-free medium.