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BackgroundWith the increasing use of nanomaterials, the need for methods and assays to examine their immunosafety is becoming urgent, in particular for nanomaterials that are deliberately administered to human subjects (as in the case of nanomedicines). To obtain reliable results, standardised in vitro immunotoxicological tests should be used to determine the effects of engineered nanoparticles on human immune responses. However, before assays can be standardised, it is important that suitable methods are established and validated.ResultsIn a collaborative work between European laboratories, existing immunological and toxicological in vitro assays were tested and compared for their suitability to test effects of nanoparticles on immune responses. The prototypical nanoparticles used were metal (oxide) particles, either custom-generated by wet synthesis or commercially available as powders. Several problems and challenges were encountered during assay validation, ranging from particle agglomeration in biological media and optical interference with assay systems, to chemical immunotoxicity of solvents and contamination with endotoxin.ConclusionThe problems that were encountered in the immunological assay systems used in this study, such as chemical or endotoxin contamination and optical interference caused by the dense material, significantly affected the data obtained. These problems have to be solved to enable the development of reliable assays for the assessment of nano-immunosafety.

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Owing to the increasing development of nanotechnology, there is a need to assess how engineered nanomaterials can interact with living cells. The main purpose of the present study was to assess whether metal cobalt nanoparticles (CoNP 100-500 nm) are genotoxic compared to cobalt ions (Co(2+)). Uptake experiments were carried out by incubating peripheral blood leukocytes (PBLs) with (57)Co(2+) (added to stable Co(2+) 10(-2) M to obtain concentrations in the range of 10(-5) to 10(-4) M) or with (60)CoNP for 24 and 48 h. Whereas intracellular Co(2+) showed slight or no variations over the baseline levels, CoNP were taken up efficiently leading to intracellular CoNP concentrations of 485 +/- 106.1 and 970 +/- 99 fg per cell after 24 and 48 h, respectively. The genotoxicity end points considered in this study were the frequency of binucleated micronucleated (BNMN) cells and the percentage of tail DNA (% Tail DNA) fragmentation by means of the comet assay. Genotoxic effects were evaluated by incubating PBLs of three healthy donors with subtoxic concentrations (10(-5) to 8 x 10(-5)M) of Co(2+) in the form of cobalt chloride, CoNP and 'washed' CoNP, the latter to exclude any interference by Co(2+). On a group basis, Co(2+) induced a clear trend in the increase of the BNMN frequency, whereas CoNP showed only minor changes. Moreover, we observed a high variability among donors in the induction of micronuclei. The comet assay showed a statistically significant dose-related increase in % Tail DNA for CoNP (P < 0,001), whereas Co(2+) did not induce significant changes over control values. These findings suggest that nanosized Co can be internalized by human leukocytes and can interact with DNA leading to the observed genotoxic effects, which are, however, modulated both by donor's characteristics and/or by Co(2+) release.

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+).