Comparative genotoxicity of nanosilver in human liver HepG2 and colon Caco2 cells evaluated by fluorescent microscopy of cytochalasin B-blocked micronucleus formation.

As a consequence of the increased use of silver nanoparticles in food, food contact materials, dietary supplements and cosmetics to prevent fungal and bacterial growth, there is a need for validated rapid screening methods to assess the safety of nanoparticle exposure. This study evaluated two widely used in vitro cell culture models, human liver HepG2 cells and human colon Caco2 cells, as tools for assessing the potential genotoxicity of 20-nm nanosilver. The average silver nanoparticle size as determined by transmission electron microscopy (TEM) was 20.4 nm. Dynamic light scattering (DLS) analysis showed no large agglomeration of the silver nanoparticles. The silver concentration in a 20-nm nanosilver solution determined by the inductively coupled plasma-mass spectrometry (ICP-MS) analysis was 0.962 mg ml(-1) . Analysis by ICP-MS and TEM demonstrated the uptake of 20-nm silver by both HepG2 and Caco2 cells. Genotoxicity was determined by the cytochalasin B-blocked micronucleus assay with acridine orange staining and fluorescence microscopy. Concentration- and time-dependent increases in the frequency of binucleated cells with micronuclei induced by the nanosilver was observed in the concentration range of 0.5 to 15 µg ml(-1) in both HepG2 and Caco2 cells compared with the control. Our results indicated that HepG2 cells were more sensitive than Caco2 cells in terms of micronuclei formation induced by nanosilver exposure. In summary, the results of this study indicate that the widely used in vitro models, HepG2 and Caco2 cells in culture, represent potential screening models for prediction of genotoxicity of silver nanoparticles by in vitro micronucleus assay.