Undetactable levels of genotoxicity of Si[O.sub.2] nanoparticles in in vitro and in vivo tests

Background: Silica dioxide (Si[O.sub.2]) has been used in various industrial products, including paints and coatings, plastics, synthetic rubbers, and adhesives. Several studies have investigated the genotoxic effects of Si[O.sub.2]; however, the results remain controversial due to variations in the evaluation methods applied in determining its physicochemical properties. Thus, well characterized chemicals and standardized methods are needed for better assessment of the genotoxicity of nanoparticles. Methods: The genotoxicity of Si[O.sub.2] was evaluated using two types of well characterized Si[O.sub.2], ie, 20 nm (-) charge (Si[O.sup.EN20(-).sub.2]) and 100 nm (-) charge (Si[O.sup.EN100(-).sub.2]). Four end point genotoxicity tests, ie, the bacterial mutation assay, in vitro chromosomal aberration test, in vivo comet assay, and in vivo micronucleus test, were conducted following the test guidelines of the Organization for Economic Cooperation and Development (OECD) with application of Good Laboratory Practice. Results: No statistically significant differences were found in the bacterial mutation assay, in vitro chromosomal aberration test, in vivo comet assay, and in vivo micronucleus test when tested for induction of genotoxicity in both two types of Si[O.sub.2] nanoparticles. Conclusion: These results suggest that Si[O.sub.2] nanoparticles, in particular Si[O.sup.EN20(-).sub.2] and Si[O.sup.EN100(-).sub.2], are not genotoxic in both in vitro and in vivo systems under OECD guidelines. Further, the results were generated in accordance with OECD test guidelines, and Good Laboratory Practice application; it can be accepted as reliable information regarding Si[O.sub.2]-induced genotoxicity. Keywords: genotoxicity test, Organization for Economic Cooperation and Development test guideline, Good Laboratory Practice, silica dioxide