Abstract
Because of wide applications of surface-modified zinc oxide nanoparticles (ZnO-NPs) in commercial sunscreens and their easiness of being released into water, concerns have been raised over their potential effects on aquatic organisms. This study compared physicochemical properties of silane-coated and uncoated ZnO-NPs to elucidate their toxic potencies toward three freshwater and three marine microalgae. Surfaces of ZnO-NPs (20 nm) were modified by coating with 3-aminopropyltrimethoxysilane (A-ZnO-NPs) that provides the particles with a more hydrophilic surface, or dodecyltrichlorosilane (D-ZnO-NPs) that turns the particles to hydrophobic. Uncoated ZnO-NPs formed larger aggregates and released more Zn2+ than did either of the two coated ZnO-NPs. The three nanoparticles formed larger aggregates but released less Zn2+ at pH 8 than at pH 7. Although sensitivities varied among algal species, A-ZnO-NPs and uncoated ZnO-NPs were more potent at inhibiting growth of algal cells than were D-ZnO-NPs after 96-h exposure to ZnO, uncoated ZnO-NPs, each of the coated ZnO-NPs or ZnSO4 at 10 concentrations ranging from 0.1 to 100 mg/L. The marine diatom Thalassiosira pseudonana exposed to ZnO-NPs, A-ZnO-NPs or D-ZnO-NPs resulted in differential expressions of genes, suggesting that each of the coatings resulted in ZnO-NPs acting through different mechanisms of toxic action.
Highlights
Due to their wide band gap of 3.37 eV at room temperature, zinc oxide nanoparticles (ZnO-NPs), with at least one dimension between 1 and 100 nm, are excellent absorbers of ultraviolet radiation of solar light[1] and are widely used in sunscreens[2] and photocatalysts[3,4,5]
Because the coating serves as a barrier between nanoparticles and the environment, and hinders generation of reactive oxygen species (ROS), Zinc oxide (ZnO)-NPs coated with HP1, a coating agent commonly used in sunscreens have lesser photocatalytic activities than do uncoated ZnO-NPs21
Seawater-based f/2 medium at higher pH facilitated aggregation of ZnO, ZnO-NPs and the two coated ZnO-NPs; whereas the freshwater-based BG-11 medium at lower pH enhanced dissolution of the four test zinc compounds after seven days of exposure
Summary
Due to their wide band gap of 3.37 eV at room temperature, zinc oxide nanoparticles (ZnO-NPs), with at least one dimension between 1 and 100 nm, are excellent absorbers of ultraviolet radiation of solar light[1] and are widely used in sunscreens[2] and photocatalysts[3,4,5]. Because the coating serves as a barrier between nanoparticles and the environment, and hinders generation of ROS, ZnO-NPs coated with HP1 (triethoxycaprylylsilane), a coating agent commonly used in sunscreens have lesser photocatalytic activities than do uncoated ZnO-NPs21. Treatment with two coated ZnO-NPs (HP1 and MAX; dimethoxydiphenylsilane and triethoxycaprylylsilane crosspolymer) or Zn2+ from ZnSO4 had little effect on these cells Such differences in toxic potencies among Zn2+, coated and uncoated ZnO-NPs were supported by differentially-expressed genes in hepatic stellate cells[22]. Dodecyltrichlorosilane, which shares a similar chemical structure with HP1, provides a hydrophobic surface to ZnO-NPs. The present study had three primary goals to: (1) compare the physicochemical characteristics of coated and uncoated ZnO-NPs among several culture media; (2) investigate their acute toxicities to selected freshwater and marine microalgae species, and (3) determine molecular mechanisms of toxic action in a marine diatom species
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
