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Physicochemical characteristics and toxicity of surface-modified zinc oxide nanoparticles to freshwater and marine microalgae.

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.

SUBMITTER: Yung MMN

PROVIDER: S-EPMC5698420 | biostudies-literature | 2017 Nov

REPOSITORIES: biostudies-literature

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Physicochemical characteristics and toxicity of surface-modified zinc oxide nanoparticles to freshwater and marine microalgae.

Yung Mana M N MMN Fougères Paul-Antoine PA Leung Yu Hang YH Liu Fangzhou F Djurišić Aleksandra B AB Giesy John P JP Leung Kenneth M Y KMY

Scientific reports 20171121 1

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-Z ...[more]

PMID: 29162907

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Project description:Zinc oxide nanoparticles (ZnO NPs) are widely used in a variety of products, thus understanding their health and environmental impacts is necessary to appropriately manage their risks. To keep pace with the rapid increase in products utilizing engineered ZnO NPs, rapid in silico toxicity test methods based on knowledge of comprehensive in vivo and in vitro toxic responses are beneficial in determining potential nanoparticle impacts. To achieve or enhance their desired function, chemical modifications are often performed on the NPs surface; however, the roles of these alterations play in determining the toxicity of ZnO NPs are still not well understood. As such, we investigated the toxicity of 17 diverse ZnO NPs varying in both size and surface chemistry to developing zebrafish (exposure concentrations ranging from 0.016 to 250 mg/L). Despite assessing a suite of 19 different developmental, behavioural and morphological endpoints in addition to mortality in this study, mortality was the most common endpoint observed for all of the ZnO NP types tested. ZnO NPs with surface chemical modification, regardless of the type, resulted in mortality at 24 hours post-fertilization (hpf) while uncoated particles did not induce significant mortality until 120 hpf. Using eight intrinsic chemical properties that relate to the outermost surface chemistry of the engineered ZnO nanoparticles, the highly dimensional toxicity data were converted to a 2-dimensional data set through principal component analysis (PCA). Euclidean distance was used to partition different NPs into several groups based on converted data (score) which were directly related to changes in the outermost surface chemistry. Kriging estimations were then used to develop a contour map based on mortality data as a response. This study illustrates how the intrinsic properties of NPs, including surface chemical modifications and capping agents, are useful to separate and identify ZnO NP toxicity to zebrafish (Danio rerio).

Project description:Owing to the peculiar broad-spectrum antimicrobial activities of zinc oxide nanoparticles (ZnO NPs), we envisaged their use to treat bacterial/mycobacterial/fungal infections during peritoneal dialysis (PD) of end-stage renal failure patients. However, a recent study from our lab showed that ZnO-NPs cannot be employed for the same in their naked form owing to their rapid agglomeration. Also, the naked ZnO-NPs showed strong interaction with organic acids present in the PD fluid (i.e., lactate and citrate present abundantly in almost all biological fluids) resulting in the formation of bioconjugates. Here, we propose that the surface coating of ZnO NPs may inhibit the binding interactions of NPs with the constituents of PD fluid. Therefore, in this study, we have carried out the surface coating of ZnO NPs with polyethylene glycol (PEG) of different molecular weights, followed by the investigations of physicochemical properties of PEGylated ZnO NPs dispersed in PD fluid using nuclear magnetic resonance (NMR) spectroscopy, dynamic light scattering (DLS), transmission electron microscopy (TEM), and Fourier transform infrared (FT-IR) spectroscopy. The interaction of PEGylated ZnO NPs has also been studied separately in glucose and lactic acid which are the main constituents of PD fluid and in citric acid. Although the X-ray diffraction and TEM results infer the colloidal stability of PEGylated ZnO NPs in PD fluid, FT-IR, UV-vis, and nuclear magnetic resonance results revealed the binding interactions of PEGylated ZnO NPs with the PD constituents. PEGylated ZnO NPs also interact strongly with the lactic acid and citric acid, leading to agglomeration, as observed previously for uncoated ZnO NPs. Further, the antibacterial activities of bare and PEG-coated ZnO NPs dispersion in PD fluid have been studied. A reduction in the bacterial inhibition effect against Staphylococcus aureus and Escherichia coli was observed for both the bare and PEG-coated ZnO NPs dispersed in PD fluid, indicating that the complex nature of PD fluid counteract on the efficiency of these nanobiotics.

Dataset Information

Physicochemical characteristics and toxicity of surface-modified zinc oxide nanoparticles to freshwater and marine microalgae.

Publications

Physicochemical characteristics and toxicity of surface-modified zinc oxide nanoparticles to freshwater and marine microalgae.

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