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Quantum Dots (QDs) are becoming more prevalent in products used in our daily lives, such as TVs and laptops, due to their unique and tunable optical properties. The possibility of using QDs as fluorescent probes in applications, such as medical imaging, has been a topic of interest for some time, but their potential toxicity and long-term effects on the environment are not well understood. In the present study, we investigated the effects of yellow CdSe/ZnS-QDs on Saccharomyces cerevisiae. We utilized growth assays, RNA-seq, reactive oxygen species (ROS) detection assays, and cell wall stability experiments to investigate the potential toxic effects of CdSe/ZnS-QDs. We found CdSe/ZnS-QDs had no negative effects on cell viability; however, cell wall-compromised cells showed more sensitivity in the presence of 10 µg/mL CdSe/ZnS-QDs compared to non-treated cells. In CdSe/ZnS-treated and non-treated cells, no significant change in superoxide was detected, but according to our transcriptomic analysis, thousands of genes in CdSe/ZnS-treated cells became differentially expressed. Four significantly differentiated genes found, including FAF1, SDA1, DAN1, and TIR1, were validated by consistent results with RT-qPCR assays. Our transcriptome analysis led us to conclude that exposure of CdSe/ZnS-QDs on yeast significantly affected genes implicated in multiple cellular processes.

InP/ZnS quantum dots (QDs) are an emerging option in QD technologies for uses of fluorescent imaging as well as targeted drug and anticancer therapies based on their customizable properties. In this study we explored effects of InP/ZnS when treated with HeLa cervical cancer cells. We employed XTT viability assays, reactive oxygen species (ROS) analysis, and apoptosis analysis to better understand cytotoxicity extents at different concentrations of InP/ZnS. In addition, we compared the transcriptome profile from the QD-treated HeLa cells with that of untreated HeLa cells to identify changes to the transcriptome in response to the QD. RT-qPCR assay was performed to confirm the findings of transcriptome analysis, and the QD mode of action was illustrated. Our study determined both IC50 concentration of 69 µg/mL and MIC concentration of 167 µg/mL of InP/ZnS. It was observed via XTT assay that cell viability was decreased significantly at the MIC. Production of superoxide, measured by ROS assay with flow cytometry, was decreased, whereas levels of nitrogen radicals increased. Using analysis of apoptosis, we found that induced cell death in the QD-treated samples was shown to be significantly increased when compared to untreated cells. We conclude InP/ZnS QD to decrease cell viability by inducing stress via ROS levels, apoptosis induction, and alteration of transcriptome.

The primary focus of our research was to obtain global gene expression data in baker’s yeast exposed to sub-lethal doses of quantum dots (QDs), such as green-emitting CdSe/ZnS and InP/ZnS, to reveal novel insights on their unique mechanisms of toxicity. Despite their promising applications, their toxicity and long-lasting effects on the environment are not well understood. To assess toxicity, we conducted cell viability assays, ROS detection assays, and assessed their effects on the trafficking of Vps10-GFP toward the trans-Golgi network with confocal microscopy. Most notably, we used RNA-sequencing (RNA-seq) to obtain gene expression profiles and gene identities of differentially expressed genes (DEGs) in QD-treated yeast. We found CdSe/ZnS QDs significantly altered genes implicated in carboxylic acid, amino acid, nitrogen compounds, protein metabolic processes, transmembrane transport, cellular homeostasis, cell wall organization, translation, and ribosomal biogenesis. Additionally, we found InP/ZnS QDs to alter genes associated with oxidation-reduction, transmembrane transport, metal ion homeostasis, cellular component organization, translation, and protein and nitrogen compound metabolic processes. Interestingly, we observed an increase in reactive oxygen species (ROS) in CdSe/ZnS-treated cells and a decrease in ROS levels in InP/ZnS-treated cells. Nevertheless, we concluded that both QDs modestly contributed cytotoxic effects on the budding yeast.

Next-generation sequencing (NGS) technology has revolutionized sequence-based research. In recent years, high-throughput sequencing has become the method of choice in studying the toxicity of chemical agents through observing and measuring changes in transcript levels. Engineered nanomaterial (ENM)-toxicity has become a major field of research and has adopted microarray and newer RNA-Seq methods. Recently, nanotechnology has become a promising tool in the diagnosis and treatment of several diseases in humans. However, due to their high stability, they are likely capable of remaining in the body and environment for long periods of time. Their mechanisms of toxicity and long-lasting effects on our health is still poorly understood. This review explores the effects of three ENMs including carbon nanotubes (CNTs), quantum dots (QDs), and Ag nanoparticles (AgNPs) by cross examining publications on transcriptomic changes induced by these nanomaterials.

Engineered Nano Materials (ENMs) are commercially used in everyday products, including zinc sunscreens and water resistant fabrics and surfaces, but in the future, they may be used in targeted treatment of cancer, printable monitoring systems, and foldable phones. Understanding the effects of ENMs on the environment is crucial for the responsible use of these technologies. The aim of this project is to develop a standard operating procedure (SOP) for investigating the effects of ENMs on budding yeast (Saccharomyces cerevisiae). The ENMs used to develop this protocol were Ag and CdSe/ZnS. Toxicity was determined using plate assays to analyze the effect of ENMs on the growth cycle, Fun-1 staining assays to understand the effects on cell metabolism, and quantitative reverse transcriptase-based polymerase chain reaction (PCR) and RNAseq to understand the effects on genetic expression. From plate assays, doubling times, average time spent in lag phase, maximum concentrations were determined and compared between yeast grown in varying concentrations of ENMs, and a yeast grown in a control environment. Fun-1 staining determines the amount of metabolically active cells present in a treated cell culture. RNAseq and Quantitative PCR results, in expression levels of genes, are used to determine potential toxic effects of ENMs. DISCLAIMER: The contents of this report are not to be used for advertising, publication, or promotional purposes. Citation of trade names does not constitute an official endorsement or approval of the use of such commercial products. All product names and trademarks cited are the property of their respective owners. The findings of this report are not to be construed as an official Department of the Army position unless so designated by other authorized documents.

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.

Our research focuses on the effects of quantum dots, CdSe/ZnS and InP/ZnS, in Saccharomyces cerevisiae. Although quantum dots have many potential and promising applications, there is much we still don't understand about their toxicity and effects on the environment. We tested our quantum dot's toxicity by conducting a series of experiments including cell viability assays, ROS detection assays, confocal microscopy, and an RNA‐seq to identify differentially expressed genes in QD‐treated yeast. We found CdSe/ZnS had no statistical effect on the growth of yeast, and InP/ZnS displayed a dose dependent effect on yeast growth. Our ROS detection experiment revealed that both QDs significantly alter ROS levels. Additionally, we found that CdSe/ZnS increased the number of Vps10‐GFP puncta and InP/ZnS decreased the number of puncta in each cell. Finally, our RNA‐seq data identified hundreds of differentially expressed genes in the presence of the quantum dots. Altogether, we concluded that CdSe/ZnS and InP/ZnS quantum dots exhibit modest and unique cytotoxic effects on the budding yeast.