Revised Procedure of the Bacterial Reverse Mutation Test for Genotoxic Evaluation of Nanoparticles

Abstract

A recent review of in vitro genotoxicity testing strategies for nanoparticles (NPs) revealed that the conventional Bacterial Reverse Mutation Test (Ames test) primarily yielded negative results, whereas the other in vitro genotoxicity assays were usually positive. Accordingly, the effi ciency of the test for NP evaluation was questioned, as was the NP entrance in bacterial cells. Indeed, prokaryotes are unable to perform endocytosis and NPs are too large to be transported through the pores of the cell wall. However, regardless of whether they have been internalized, the mutagenic potential of free radicals, produced intrinsically or indirectly by NPs adsorbed onto the bacterial cell walls, should be detected by the Bacterial Reverse Mutation Test .Another phenomenon that can explain the low test effi ciency is the lack of interactions between NPs and cells due to strong NP aggregation in the exposure medium of the assay and the presence of electrostatic repulsive forces between NPs and bacteria, which both carry overall negative charge. This hypothesis is supported by our recent study that revealed the mutagenic potential of NP-TiO 2 using a revised procedure of the Bacterial Reverse Mutation Test , which improves the NP-cell interactions and the sensitivity of the test.In this chapter, we provide several recommendations for the genotoxic evaluation of NPs and propose a revised version of the Bacterial Reverse Mutation Test more in line with the specifi c properties of NPs.