Exposure to High Dosage of Gold Nanoparticles Accelerates Growth Rate by Modulating Ribosomal Protein Expression.

Abstract Gold nanoparticles (AuNPs) have been utilized in various biomedical applications, including diagnostics and drug delivery. However, cellular and metabolic responses of cells to these particles remain poorly characterized. In this study, we used bacteria ( Escherichia coli and Bacillus subtilis ) and a fungus ( Saccharomyces cerevisiae ) as model organisms to investigate the cellular and metabolic effects of exposure to different concentrations of citrate-capped spherical AuNPs with diameters of 5 and 10 nm. Our data showed the stability of synthesized AuNPs in different growth media and revealed comparable uptake by microorganisms. An exposure to a high concentration of AuNPs (10 12 particles) resulted in reduced cell-division time and a two-fold increase in cell density in both bacteria and unicellular eukaryote. The exposed cells exhibited a decrease in average cell size and an increase in the cell-division marker protein (FtsZ), further supporting an accelerate growth rate. Notably, exposure to such high dosage of AuNPs did not induce DNA damage, envelope stress, or a general stress response in bacteria. Differential whole proteome analysis demonstrated modulation of ribosomal protein expression upon exposure to AuNPs in both E. coli and S. cerevisiae . Interestingly, the accelerated growth observed in the presence of AuNPs was sensitive to sub-MIC dosages of a drug that specifically targets ribosome assembly and recycling. Based upon these findings, we argue that exposure to high concentrations of AuNPs induces stress on the translation machinery. This leads to an increase in protein synthesis rate by modulating ribosome assembly, which results in the rapid proliferation of cells.