Article

Effects of zinc oxide and titanium dioxide nanoparticles on green algae under visible, UVA, and UVB irradiations: No evidence of enhanced algal toxicity under UV pre-irradiation.

Department of Environmental Science, Konkuk University, 1 Hwayang-dong, Gwangjin-gu, Seoul 143-701, Republic of Korea.
Chemosphere (Impact Factor: 3.14). 01/2013; DOI: 10.1016/j.chemosphere.2012.12.033
Source: PubMed

ABSTRACT Some metal oxide nanoparticles are photoreactive, thus raising concerns regarding phototoxicity. This study evaluated ecotoxic effects of zinc oxide nanoparticles and titanium dioxide nanoparticles to the green algae Pseudokirchneriella subcapitata under visible, UVA, and UVB irradiation conditions. The nanoparticles were prepared in algal test medium, and the test units were pre-irradiated by UV light in a photoreactor. Algal assays were also conducted with visible, UVA or UVB lights only without nanoparticles. Algal growth was found to be inhibited as the nanoparticle concentration increased, and ZnO NPs caused destabilization of the cell membranes. We also noted that the inhibitory effects on the growth of algae were not enhanced under UV pre-irradiation conditions. This phenomenon was attributed to the photocatalytic activities of ZnO NPs and TiO(2) NPs in both the visible and UV regions. The toxicity of ZnO NPs was almost entirely the consequence of the dissolved free zinc ions. This study provides us with an improved understanding of toxicity of photoreactive nanoparticles as related to the effects of visible and UV lights.

0 Bookmarks
 · 
252 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: ABSTRACT The in vitro genotoxic and the soft agar anchorage independent cell transformation ability of zinc oxide nanoparticles (NPs) and its bulky forms have been evaluated in human embryonic kidney (HEK293) and in mouse embryonic fibroblast (NIH/3T3) cells, either alone or in combination with UVB-light. The comet assay, with and without the use of FPG and Endo III enzymes, the micronucleus assay and the softagar colony assay were used. For the comet assay a statistically significant induction of DNA damage, with and without the enzymes, were observed up of 100 μg/mL. ZnO NPs were able to increase significantly the frequency of micronuclei, and similar results were observed in the cell transformation assay where such NPs were able to induce cell-anchorage independent growth. These effects were observed at doses up 100 μg/mL. Although UVB-light was able to induce genotoxic damage and cellanchorage growth, a significant antagonist interaction effect was observed in combination with ZnO NPs. These in vitro results, obtained with the selected cell lines, contribute to increase our genotoxicity database on the ZnO NPs effects as well as to open the discussion about their risk in photo-protection sun screens.
    Journal of Hazardous Materials 11/2013; · 3.93 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Aquatic nanotoxicologists and ecotoxicologists have begun to identify the unique properties of the nanomaterials (NM) that potentially impact the health of wildlife. In this review the scientific aims are to discuss the main challenges nanotoxicologists currently face in aquatic toxicity testing, including the transformations of NM in aquatic test media (dissolution, aggregation, and small molecule interactions), and modes of NM interference (optical interference, adsorption to assay components, and generation of reactive oxygen species) on common toxicity assays. Three of the major OECD (Organisation for Economic Co-operation and Development) priority materials, titanium dioxide (TiO2), zinc oxide (ZnO), and silver (Ag) NM, studied recently by the NRC-NSERC-BDC Nanotechnology Initiative (NNBNI), a Canadian consortium, have been identified to cause both bulk effect, dissolution-based (i.e. free metal), and/or NM-specific toxicity in aquatic organisms. TiO2 NM are most toxic to algae, with toxicity being NM size-dependent and principally associated with binding of the materials to the organism. Conversely, dissolution of Zn and Ag NM and the subsequent release of their ionic metal counterparts appear to represent the primary mode of toxicity to aquatic organisms for these NM. In recent years, our understanding of the toxicological properties of these specific OECD relevant materials has increased significantly. Specifically, researchers have begun to alter their experimental design to identify the different behaviour of these materials as colloids, and by introducing appropriate controls and NM characterization, aquatic nanotoxicologists are now beginning to posses a clearer understanding of the chemical and physical properties of these materials in solution, and how these materials may interact with organisms. Arming nanotoxicologists with this understanding, combined with knowledge of the physics, chemistry and biology of these materials is essential for maintaining the accuracy of all future toxicological assessments.
    Environmental Chemistry 05/2014; · 2.65 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The effect of ultraviolet-A irradiated or nonirradiated suspensions of agglomerates of titanium dioxide (TiO(2)) or silicon dioxide (SiO(2)) nanoparticles on roots of the onion (Allium cepa) has been studied. The reactive potential of TiO(2) nanoparticles, which have photocatalytic potential, and the nonphotocatalytic SiO(2) nanoparticles with the same size of agglomerates was compared. The authors measured the activity of antioxidant enzymes glutathione reductase, ascorbate peroxidase, guaiacol peroxidase, and catalase as well as lipid peroxidation to assess the oxidative stress in exposed A. cepa roots. A wide range of concentrations of nanoparticles was tested (0.1-1000 µg/mL). The sizes of agglomerates ranged in both cases from 300 nm to 600 nm, and the exposure time was 24 h. Adsorption of SiO(2) nanoparticles on the root surface was minimal but became significant when roots were exposed to TiO(2) agglomerates. No significant biological effects were observed even at high exposure concentrations of SiO(2) and TiO(2) nanoparticles individually. Plants appear to be protected against nanoparticles by the cell wall, which shields the cell membrane from direct contact with the nanoparticles. The authors discuss the need to supplement conventional phytotoxicity and stress end points with measures of plant physiological state when evaluating the safety of nanoparticles.
    Environmental Toxicology and Chemistry 04/2014; 33(4):858-67. · 2.62 Impact Factor

Full-text

View
132 Downloads
Available from
May 19, 2014