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
 · 
338 Views
  • 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; · 3.04 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Zinc oxide nanoparticles (ZnO NPs) are largely used in consumer products and industrial applications. The increased use of such materials may lead to its release into the environment. The study used chemically synthesized ZnO NPs and characterized by using UV-visible spectrophotometer, scanning electron microscopy, particle size analyzer and X-ray diffraction (XRD) analysis. The mean diameter of the particles was found to be 55±1.2nm. The XRD patterns exhibited hexagonal structure for ZnO NPs. The photocatalytic property of ZnO NPs was evaluated based on the UV-vis spectra changes of the methylene blue solution as a function of reaction time in the presence of ZnO NPs under visible light. The study suggests that ZnO NPs can be used as an efficient photocatalyst and the environmental factor such as exopolysaccharides could mask the photocatalytic activity of NPs.
    Colloids and surfaces B: Biointerfaces 08/2014; · 4.28 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. · 2.83 Impact Factor

Full-text

Download
264 Downloads
Available from
May 19, 2014