Current high-throughput screening of nanotoxicity on bacteria viability relies largely on optical assays, including assays using luminescence and absorbance. However, because nanomaterials often display optical properties of their own, interference by nanomaterials in optical assays can be significant. Herein, we developed a bacterial viability assay that is free of interference from nanomaterials and can be performed in a high-throughput format on 96-well plates in a plate reader. Bacteria were exposed to various materials, and then diluted into fresh growth medium by a large amount. The fraction of viable cells after exposure grew in fresh medium and generated measured growth curves. Bacterial viability was quantitatively correlated to the delay of bacterial growth compared to a reference that started with 100% viability; data analysis was inspired by that in quantitative polymerase chain reactions, where the delay in the amplification curve is correlated to the starting amount of template nucleic acid. The large dilution ensured minimal optical interference from the nanomaterial when reading optical density, and the residue left from the exposure mixture after dilution was confirmed not to affect the bacterial growth profile. Fast and robust data analysis was achieved by developing computer algorithms carried out in R code. To date, this growth-based bacterial viability (GBV) assay has been tested on four bacterial strains, showing great potential of application to all culturable bacterial strains. With the increasing diversity of engineered nanomaterials being considered for large-scale use, this high-throughput screening method may facilitate the rapid screening of nanomaterial toxicity and thus inform the risk assessment of nanoparticles in a timely fashion.

Growth-based Bacterial Viability (GBV) assay for interference-free and high-throughput nanotoxicity screening

253rd National Meeting (2017)

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