Toxicity and assimilation of cellulosic copper nanoparticles require α-arrestins in S. cerevisiae.

The incorporation of antimicrobial compounds such as copper into nanoparticles changes how living cells interact with these novel materials. Increased use of antimicrobial nanomaterials combats infectious disease and food spoilage. Fungal infections are particularly difficult to compact because of the few druggable targets, and S. cerevisiae provides an insightful model organism to test these new materials. However, because of the novel characteristics of these materials, it is unclear how these materials interact with living cells and if resistance to copper-based nanomaterials could occur. Copper nanoparticles built on CarboxylMethylCelluose microfibril strands with copper (CMC-Cu) are a promising nanomaterial when imported into yeast cells and induce cell death. α-arrestins are cargo adaptors that select which molecules are imported into eukaryotic cells. We screened α-arrestins mutants and identified Aly2, Rim8, and Rog3 α-arrestins which are necessary for the internalization of CMC-Cu nanoparticles. Internal reactive oxygen species (ROS) in these mutants were lower and corresponded to the increased viability in the presence of CMC-Cu. Using lattice light-sheet microscopy on live cells, we determined that CMC-Cu were imported into yeast within 30 minutes of exposure. Initially, the cytoplasmic pH decreased but returned to basal level 90 minutes later. However, there was heterogeneity in response to CMC-Cu exposure which could be due to the heterogeneity of the particles or differences in the metabolic states within the population. When yeast were exposed to sublethal concentrations of CMC-Cu no resistance occurred. Internalization of CMC-Cu increases the potency of these antimicrobial nanomaterials and is likely key to preventing fungi from evolving resistance.