No abstract

The widespread use of nanoparticles (NPs) raises concern over their potential toxicological effects in humans and ecosystems. Here we used transcriptome sequencing (RNA-seq) to evaluate the effects of exposure to four different metal-based NPs, nano-Ag (nAg), nano-TiO 2 (nTiO 2 ), nano-ZnO (nZnO), and CdTe/CdS quantum dots (QDs), in the eukaryotic green alga Chlamydomonas reinhardtii. The transcriptome was characterized before and after exposure to each NP type. Specific toxicological effects were inferred from the functions of genes whose transcripts either increased or decreased. Data analysis resulted in important differences and also similarities among the NPs. Elevated levels of transcripts of several marker genes for stress were observed, suggesting that only nZnO caused nonspecific global stress to the cells under environmentally relevant conditions. Genes with photosynthesis-related functions were decreased drastically during exposure to nTiO 2 and slightly during exposures to the other NP types. This pattern suggests either toxicological effects in the chloroplast or effects that mimic a transition from low to high light. nAg exposure dramatically elevated the levels of transcripts encoding known or predicted components of the cell wall and the flagella, suggesting that it damages structures exposed to the external milieu. Exposures to nTiO 2 , nZnO, and QDs elevated the levels of transcripts encoding subunits of the proteasome, suggesting proteasome inhibition, a phenomenon believed to underlie the development and progression of several major diseases, including Alzheimer's disease, and used in chemotherapy against multiple myeloma. N anoparticles (NPs) are materials with at least one dimension in the nanoscale (ca. 1 to 100 nm), with resulting size-related physicochemical properties that differ from those of their bulk counterparts. Specifically, their high surface-to-volume ratio generally results in highly reactive and physicochemically dynamic materials. With the increasing use of engineered NPs, there is an enormous uncertainty with respect to their potential environmental impacts, including their toxicological effects. Of special concern is the emerging evidence that numerous NPs can produce reactive oxygen species (ROS), release toxic metals, or react directly with the biological membrane (1, 2). A major key question is whether toxicological effects are due to general properties shared by diverse NP types or whether they are specific to each NP. For example, if toxicological effects are related to the size, shape, or agglomeration of the NP, then different NP compositions would likely exert similar effects (3), whereas distinct toxicological effects would be expected if particle composition controls the interaction with the biological surface (4, 5). An understanding of the toxicological effects of each NP type is critical for any prediction of their immediate and long-term risks for humans and ecosystems.A powerful approach to determine how an organism responds to a particular abiotic condition...

In order to properly assess the environmental risk of engineered nanoparticles (ENP), it is necessary to determine their fate (including dissolution, aggregation, and bioaccumulation) under representative environmental conditions. CdTe/CdS quantum dots (QD), such as those used in medical imaging, are known to release Cd(2+) due (mainly) to the dissolution of their outer shell. In this study, Chlamydomonas reinhardtii was exposed to either a soluble Cd salt or QD at similar concentrations of total Cd. Free Cd concentrations were measured using the Absence of Gradients and Nernstian Equilibrium Stripping technique. QD dissolution increased with decreasing pH and with increasing QD concentration. When exposed to QD, bioaccumulation was largely accounted for by dissolved Cd. Nonetheless, QD were shown to be taken up by the cells and to provoke unique biological effects. Whole transcriptome screening using RNA-Seq analysis showed that the free Cd and the QD had distinctly different biological effects.

An on-line SPE-UHPLC-HRMS method was optimized for filtration, on-line SPE, and HRMS conditions for the rapid screening of 17 cyanotoxins. 8 cyanotoxins were detected with 75% of lakes containing MC-LR and 38% containing anabaenopeptins (A or B).