Comparing Transcriptome Profiles of Silver, Cadmium Selenide/Zinc Sulfide, Indium Phosphide/Zinc Sulfide, and Palladium Quantum Dots in Saccharomyces cerevisiae

Abstract

The primary focus of our research is to obtain global gene expression data in baker’s yeast exposed to sub‐lethal doses of specific nanomaterials, such as nanoparticles (NPs) and quantum dots (QDs), to reveal novel insights on their mysterious and undetermined mechanisms of toxicity. We have investigated the negative effects of several nanomaterials including Silver nanoparticles (AgNPs) and yellow emitting Cadmium Selenide/Zinc Sulfide (CdSe/ZnS) QDs, and are continuing our investigation on other nano‐materials like green emitting CdSe/ZnS QDs, Indium Phosphide/Zinc Sulfide (InP/ZnS) QDs, and Palladium nanoparticles (PdNPs). Despite their promising and ever‐growing list of applications (fluorescent probes, drug delivery systems, etc.) their potential toxicity and long lasting effects on the environment are not well understood. Using high‐throughput technology, such as RNA‐sequencing, we obtained gene expression profiles and the identities of specific differentially expressed genes (DEGs) in yeast exposed to our wide variety of nanomaterials. We have found hundreds of DEGs in cells treated with AgNPs involved in rRNA processing, ribosome biogenesis, cell wall formation, cell membrane integrity, and mitochondrial functions. Additionally, our cell wall stability experiment revealed cells treated with AgNPs were extremely susceptible to cell wall damage. Further, we found hundreds more DEGs in yellow emitting CdSe/ZnS treated cells than in Ag treated cells leading us to conclude that both Ag and CdSe/ZnS treated cells induced a mild cytotoxic effect in yeast. Due to the versatile nature of nanoscale materials, their mechanisms of toxicity can differ vastly based on their physical characteristics. Currently, we are analyzing gene expression profiles of a similar green emitting CdSe/ZnS QD, a “safer” InP/ZnS QD, and PdNPs to determine a better understanding of how these materials induce toxicity. Interestingly, we have noted differences in DEGs between yellow and green emitting CdSe/ZnS QDs, such as fewer DEGs involved in RNA processing and ribosome biogenesis, indicating the two similar QDs may have different mechanisms of toxicity. To our knowledge, we are the first to investigate and compare DEGs induced by these nanomaterials in yeast using RNA‐sequencing. Additionally, we expect and anticipate that our findings will help provide useful data on the toxicity of certain nanomaterials and will expedite change in the EPA’s current regulations and standards on the use of such nanomaterials.