Toxicity assessment of manufactured nanomaterials using the unicellular green alga Chlamydomonas reinhardtii. Chemosphere, 73, 1121-1128

Department of Civil and Environmental Engineering, Arizona State University, Tempe, AZ 85287, USA
Chemosphere (Impact Factor: 3.34). 10/2008; 73(7):1121-1128. DOI: 10.1016/j.chemosphere.2008.07.040


With the rapid development of nanotechnology, there is an increasing risk of human and environmental exposure to nanotechnology-based materials and products. As water resources are particularly vulnerable to direct and indirect contamination of nonomaterials (NMs), the potential toxicity and environmental implication of NMs to aquatic organisms must be evaluated. In this study, we assessed potential toxicity of two commercially used NMs, titanium dioxide (TiO2) and quantum dots (QDs), using the unicellular green alga Chlamydomonas reinhartii as a model system. The response of the organism to NMs was assessed at physiological, biochemical, and molecular genetic levels. Growth kinetics showed that growth inhibition occurred during the first two to three days of cultivation in the presence of TiO2 or QDs. Measurements of lipid peroxidation measurement indicated that oxidative stress of the cells occurred as early as 6 h after exposure to TiO2 or QDs. The transcriptional expression profiling of four stress response genes (sod1, gpx, cat, and ptox2) revealed that transient up-regulation of these genes occurred in cultures containing as low as 1.0 mg L−1 of TiO2 or 0.1 mg L−1 of QDs, and the maximum transcripts of cat, sod1, gpx, and ptox2 occurred at 1.5, 3, 3, and 6 h, respectively, and were proportional to the initial concentration of the NMs. As the cultures continued, recovery in growth was observed and the extent of recovery, as indicated by the final cell concentration, was dosage-dependent. QDs were found to be more toxic to Chlamydomonas cells than TiO2 under our experimental conditions.

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    • "2.3.3. Oxidative stress assessment (ROS) Intracellular reactive oxygen species (ROS) such as hydroxyl radical OH − and superoxide anion were detected using cell-permeable dye, 2 -7 -dichlorofluorescein-diacetate (DCFH-DA) (Wang et al., 2008; Dalai et al., 2014). For cellular ROS staining, 100 ␮M DCFH-DA was added to 5 mL of control and NPs-treated culture, followed by 30 min incubation under dark condition. "
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    ABSTRACT: Continuous increase in the usage of ZnO nanoparticles in commercial products has exacerbated the risk of release of these particles into the aquatic environment with possible harmful effects on the biota. In the current study, cytotoxic effects of two types of ZnO nanoparticles, having different initial effective diameters in filtered and sterilized lake water medium [487.5±2.55nm for ZnO-1 NPs and 616.2±38.5nm for ZnO-2 NPs] were evaluated towards a dominant freshwater algal isolate Scenedesmus obliquus in UV-C, visible and dark conditions at three exposure concentrations: 0.25, 0.5 and 1mg/L. The toxic effects were found to be strongly dependent on the initial hydrodynamic particle size in the medium, the exposure concentrations and the irradiation conditions. The loss in viability, LDH release and ROS generation were significantly enhanced in the case of the smaller sized ZnO-1 NPs than in the case of ZnO-2 NPs under comparable test conditions. The toxicity of both types of ZnO NPs was considerably elevated under UV-C irradiation in comparison to that in dark and visible light conditions, the effects being more enhanced in case of ZnO-1 NPs. The size dependent dissolution of the ZnO NPs in the test medium and possible toxicity due to the released Zn(2+) ions was also noted. The surface adsorption of the nanoparticles was substantiated by scanning electron microscopy. The internalization/uptake of the NPs by the algal cells was confirmed by fluorescence microscopy, transmission electron microscopy, and elemental analyses. Copyright © 2015 Elsevier B.V. All rights reserved.
    Full-text · Article · Mar 2015 · Aquatic Toxicology
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    • "Braydich-Stolle et al. (2009) have observed that rutile TiO 2 NPs were capable of initiating apoptosis through the formation of ROS, whereas pure anatase TiO 2 NPs caused cell necrosis and membrane leakage in cells. Most of the previous toxicity studies on microalgae dealt with the anatase phase and P25 form of TiO 2 (Chen et al., 2012; Clement et al., 2013; Dalai et al., 2013; Lee and An, 2013; Wang et al., 2008) and only a handful studies are available with the rutile phase (Ji et al., 2011). Therefore, it is pertinent to study the other crystalline phase, i.e., rutile TiO 2 NPs, which is also commonly employed in commercial products/applications (Winkler, 2003; Yu et al., 2013). "
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    ABSTRACT: In view of the increasing usage of anatase and rutile crystalline phases of titania NPs in the consumer products, their entry into the aquatic environment may pose a serious risk to the ecosystem. In the present study, the possible toxic impact of anatase and rutile nanoparticles (individually and in binary mixture) was investigated using freshwater microalgae, Chlorella sp. at low exposure concentrations (0.25, 0.5 and 1mg/L) in freshwater medium under UV irradiation. Reduction of cell viability as well as a reduction in chlorophyll content were observed due to the presence of NPs. An antagonistic effect was noted at certain concentrations of binary mixture such as (0.25, 0.25), (0.25, 0.5), and (0.5, 0.5) mg/L, and an additive effect for the other combinations, (0.25, 1), (0.5, 0.25), (0.5, 1), (1, 0.25), (1, 0.5), and (1, 1) mg/L. The hydrodynamic size analyses in the test medium revealed that rutile NPs were more stable in lake water than the anatase and binary mixtures [at 6h, the sizes of anatase (1mg/L), rutile NPs (1mg/L), and binary mixture (1, 1mg/L) were 948.83±35.01nm, 555.74±19.93nm, and 1620.24±237.87nm, respectively]. The generation of oxidative stress was found to be strongly dependent on the crystallinity of the nanoparticles. The transmission electron microscopic images revealed damages in the nucleus and cell membrane of algal cells due to the interaction of anatase NPs, whereas rutile NPs were found to cause chloroplast and internal organelle damages. Mis-shaped chloroplasts, lack of nucleus, and starch-pyrenoid complex were noted in binary-treated cells. The findings from the current study may facilitate the environmental risk assessment of titania NPs in an aquatic ecosystem. Copyright © 2015 Elsevier B.V. All rights reserved.
    Full-text · Article · Feb 2015 · Aquatic Toxicology
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    • "The unicellular alga Chlamydomonas reinhardtii is a useful model to study stress responses; growth of this alga is rapid with a short generation time, attaining logarithmic growth phase in two days, and the entire genome of this organism has been sequenced as part of the Chlamydomonas Genome Project ( This microalga is also highly sensitive to a wide range of trace elements, nanomaterials and organic chemicals with quantifiable responses at the genomic and cellular levels (Wang et al., 2008; Elbaz et al., 2010; Altenburger et al., 2012; Petit et al., 2012). Previous studies have demonstrated that perfluoroalkyl substances (PFAS) such as perflurooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) may cause significant reduction of algae growth and biomass (Latała et al., 2009; Mitchell et al., 2011; Xu et al., 2013). "
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    ABSTRACT: Perfluoroalkyl phosphonic acids (PFPAs), a new class of perfluoroalkyl substances used primarily in the industrial sector as surfactants, were recently detected in surface water and wastewater treatment plant effluents. Toxicological effects of PFPAs have as yet not been investigated in aquatic organisms. The objective of the present study was to evaluate the effects of perfluorooctylphosphonic acid (C8-PFPA) and perfluorodecylphosphonic acid (C10-PFPA) exposure (31-250 μg/L) on Chlamydomonas reinhardtii using genomic (qRT-PCR), biochemical (reactive oxygen species production (ROS) and lipid peroxidation), and physiological (cellular viability) indicators. After 72 hr of exposure, no differences were observed in cellular viability for any of the two perfluorochemicals. However, increase in ROS concentrations (36% and 25.6% at 125 and 250 μg/L, respectively) and lipid peroxidation (35.5% and 35.7% at 125 and 250 μg/L, respectively) were observed following exposure to C10-PFPA. C8-PFPA exposure did not impact ROS production and lipid peroxidation in algae. To get insights into the molecular response and modes of action of PFPA toxicity, qRT-PCR-based assays were performed to analyze the transcription of genes related to antioxidant responses including superoxide dismutase (SOD-1), glutathione peroxidase (GPX), catalase (CAT), glutathione S-transferase (GST), and ascorbate peroxidase (APX I). Genomic analyses revealed that the transcription of CAT and APX I was up-regulated for all the C10-PFPA concentrations. In addition, PFPAs were quantified in St. Lawrence River surface water samples and detected at concentrations ranging from 250 to 850 pg/L for C8-PFPA and 380 to 650 pg/L for C10-PFPA. This study supports the prevalence of PFPAs in the aquatic environment and suggests potential impacts of PFPA exposure on the antioxidant defensive system in C. reinhardtii.
    Full-text · Article · Dec 2014 · Aquatic Toxicology
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