The in vitro micronucleus assay detects small membrane bound DNA fragments (micronuclei) in the cytoplasm of interphase cells. The assay measures the clastogenicity (chromosome breakage) and aneugenicity (changes in chromosome number) of test chemicals in cells that have undergone cell division during or after exposure [23]. There are a number of studies on the genotoxicity of nanomaterials in the assay, with most of the positive responses involving tests conducted on TiO2 nanoparticles [24], [25], [26], [27] and [28]. Other nanoparticles such as a nano-sized cobalt–chromium alloy [29], SiO2 [30] and water soluble C60 fullerenes (C60(OH)24) [31] also induced elevated micronucleus frequencies. While single-walled carbon nanotubes produced no significant increase in micronucleus frequency [19], multi-walled carbon nanotubes were positive in the assay [32]. In addition, starch-coated AgNPs tested positive in normal human lung fibroblast cells (IMR-90) and human glioblastoma cells (U251) using the cytokinesis blocked version of the micronucleus assay [33].