Amine Mezni

Effect of permethrin, anthracene and mixture exposure on shell components, enzymatic activities and proteins status in the Mediterranean clam Venerupis decussata

Anthracene (ANT) and permethrin (PER) are two of the more toxic compounds reaching the marine environment. This study aimed to determine the impact of these molecules on Venerupis decussata, an economically important species cultured on the Tunisian coast. Shell structure and its possible transformation upon exposure to the two contaminants were studied by X-ray diffraction and gravimetric analyses. Results revealed a phase transition in shell composition from aragonite to calcite after PER exposure, to a mixture of PER and ANT (Mix) but not for ANT alone. Catalase (CAT), superoxide dismutase (SOD) and glutathione transferase (GST) activities were determined in digestive gland and gills after exposure to ANT, PER and Mix to assess the impact of the contamination on the oxidative status of V. decussata. Enzyme activities increased in the digestive gland after PER treatment and in the gills after ANT treatment. PER exposure significantly reduced the levels of free thiols and increased levels of carbonylated proteins in the digestive gland, as compared to controls. In contrast, ANT exposure significantly reduced free thiols and increased the number of carbonylated proteins in the gills. Mix induced additive effects as measured by both enzymatic and proteomic approaches. The present study suggests that PER has a strong effect on shell structure; that PER and ANT exposure generate compound-dependent oxidative stress in the tissues of V. decussata and that a mixture of the two compounds has synergistic effects on biochemical response.

Size- and shape-controlled synthesis of well-organised carbon nanotubes using nanoporous anodic alumina with different pore diameters

This work aims at introducing the synthesis process of carbon nanotubes (CNTs) inside nanoporous anodic alumina (NAA) templates adopting a catalyst-free chemical vapor deposition (CVD) approach under different conditions. The nanotubular structure of NAA is prepared according to tow-step anodization process. This provides a unique platform to grow CNTs with precisely controlled geometric features. The structural features, crystalline structures and chemical composition of the resulting CNTs-NAA composites were systematically characterized using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM), High Resolution Transmission Electron Microscopy (HRTEM), X-ray Diffraction (XRD), X-ray Photoelectron Spectroscopy (XPS), Energy-dispersive X-ray spectroscopy (EDX), Fourier Transform Infrared Spectroscopy (FTIR) as well as Raman spectroscopy. Preparing the CNTs according to this template technique allows us to obtain nanotubes which are open at one/both end(s) with a uniform diameter (10-200nm) along the pore length (1-100μm) without using any metal catalyst.

Facile synthesis of highly thermally stable TiO2 photocatalysts

A new and facile method of synthesizing high-temperature stable titanium dioxide (TiO2) nanoparticles (NPs) is presented in this work. This novel approach allows the production of titanium dioxide nanoparticles owing to a modified solvothermal process that makes use of titanium(IV) butoxide as a titanium precursor and Dimethyl Sulfoxide (DMSO) as a solvent. The structure and morphology of the TiO2 nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectrometry (EDX) and high-resolution transmission electron microscopy (HRTEM). Based on FTIR and TDA/TGA measurements, a proposed mechanism for the formation of TiO2 NPs in DMSO (without adding any other reagents) is discussed in this contribution. Optical absorption measurements showed that the TiO2 nanoparticles exhibited a UV significant absorption peak clearly blue-shifted with respect to that of bulk TiO2. The results showed that monodisperse quasi-spherical TiO2 nanoparticles (with an average size of 11 nm) consisting of a pure anatase phase were formed. The titanium dioxide nanoparticles showed a high photocatalytic performance in the degradation of diuron pesticide (C9H10Cl2N2O) under illumination by UV light. The high crystalline quality, together with the easy synthesis process, makes TiO2 nanoparticles a promising candidate for many applications, such as optoelectronics and water photolysis for hydrogen production.

Facile Synthesis of Cu Doped Au–ZnS Photocatalyst

In this work, we report on the synthesis of of Cu-doped Au–ZnS nanoparticles (Au–Zn1−xCuxS; where x = 0.00, 0.1 and 1%) using a one-pot chemical method that makes use of 1,3-propanediol as a solvent, a reducting agent and a stabilizing layer. The structure and morphology of the as prepared nanoparticles were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD) and energy dispersive X-ray spectrometry (EDX). Optical extinction measurements showed that the Cu-doped Au–ZnS nanoparticles exhibit a localized surface plasmon resonance (SPR) clearly red-shifted with respect to that of bare Au nanoparticles (AuNPs). In addition, it was found that the optical band gaps of Cu-doped ZnS nanocrystals blue-shifted (i.e., the band gap widening) to shorter wavelength compared to pure ZnS nanocrystals. Photocatalytic activities of Cu-doped Au–ZnS nanocomposites were evaluated by the degradation of 4-Nitrophenol under illumination by solar light. Enhanced performances compared either to undoped Au–ZnS nanocomposites were observed. The effect of various parameters was investigated on the photocatalytic activities of Cu-doped Au–ZnS nanocomposites.

Titanium dioxide nanoparticles: synthesis, characterisations and aquatic ecotoxicity effects

ABSTRACT Little information is available on the potential ecotoxicity of nanomaterials in the marine environment. In particular, the aquatic ecotoxicity impact of titanium dioxide (TiO2) has been rarely reported. To carefully address this issue, we report on the synthesis of TiO2 NPs using solvothermal process. The structure and morphology of the prepared TiO2 nanoparticles were characterised using different techniques. To study the potential ecotoxicity effect of TiO2, antioxidant system of mediterranean bivalves (Mytilus galloprovincialis) was used, measuring three oxidative biomarkers (ROS production, SOD activity and GSH/GSSG level). No considerable effect was found in the digestive glands of any of the groups treated with TiO2 with concentration gradients ranging from 1 to 100 mg/L. Thus, the level of the superoxide anion, the activity of an antioxidant enzyme superoxide dismutase (SOD) and the GSH/GSSG ratio showed no significantly differences in digestive glands of all treated groups compared to the control. However, slight modifications were observed in the gills at high concentrations. These results demonstrated that TiO2 appears to exert little toxicity on marine mussels after a short-term exposure at high concentration. However, before considering the use of this nanomaterial in various applications, further complementary studies are required in order to ensure the environmental safety of these NPs.

Effect of exposure time, particle size and uptake pathways in immune cell lysosomal cytotoxicity of mussels exposed to silver nanoparticles

Abstract Cytotoxicity evaluation of hemocytes (lysosomal membrane stability [LMS] assay) from Mytilus galloprovincialis Lamarck, exposed to a sublethal dose (100 μg/L) of two size of silver nanoparticles (AgNPs: <50 nm and <100 nm) – prior to and after inhibition of potential uptake pathways (i.e., clathrin- and caveolae-mediated endocytosis) within different times of exposure (3, 6, 12 h) – showed that there was a significant cytotoxic effect on immune cells of mussels exposed for different times to either AgNP size (p < 0.01); the greater effect was with the smaller size. However, hemocytes seemed more sensitive to the larger AgNP after clathrin-mediated endocytosis was blocked (p < 0.01); this was not so with inhibition of caveolae-mediated endocytosis. Dimethyl-sulfoxide (DMSO) did not impart a carrier-mediated effect despite an enhanced cytotoxicity when DMSO was present with AgNP. From these results, it is concluded that the immunotoxicity of AgNP in mussels was size-dependent as well as length of exposure-dependent. It was also clear that nanoparticles (NP) internalization mechanisms were a major factor underlying any toxicity.

Construction of a Novel Three-Dimensional PEDOT/RVC Electrode Structure for Capacitive Deionization: Testing and Performance

This article discusses the deposition of different amount of microstuctured poly(3,4-ethylenedioxythiophene) (PEDOT) on reticulated vitreous carbon (RVC) by electrochemical method to prepare three-dimensional (3D) PEDOT/RVC electrodes aimed to be used in capacitive deionization (CDI) technology. A CDI unit cell has been constructed here in this study. The performance of CDI cell in the ion removal of NaCl onto the sites of PEDOT/RVC electrode has been systematically investigated in terms of flow-rate, applied electrical voltage, and increasing PEDOT loading on PEDOT/RVC electrodes. It is observed that the increase in flow-rate, electric voltage, and PEDOT loading up to a certain level improve the ion removal performance of electrode in the CDI cell. The result shows that these electrodes can be used effectively for desalination technology, as the electrosorption capacity/desalination performance of these electrodes is quite high compared to carbon materials. Moreover, the stability of the electrodes has been tested and it is reported that these electrodes are regenerative. The effect of increasing NaCl concentration on the electrosorption capacity has also been investigated for these electrodes. Finally, it has been shown that 1 m3 PEDOT-120 min/RVC electrodes from 75 mg/L NaCl feed solution produce 421, 978 L water per day of 20 mg/L NaCl final concentration.

Toxicity assessment of ZnO-decorated Au nanoparticles in the Mediterranean clam Ruditapes decussatus.

The synthesis of hybrid nanomaterials has greatly increased in recent years due to their special physical and chemical properties. However, information regarding the environmental toxicity associated with these chemicals is limited, in particular in the aquatic environment. In the present study, an experiment was performed in which the marine bivalve (Ruditapes decussatus) was exposed for 14days to 2 concentrations of zinc oxide-decorated Au nanoparticles (Au-ZnONPs: Au-ZnONP50=50μg/L; Au-ZnONP100=100μg/L). The stability and resistance of Au-ZnONPs in the natural seawater were assessed by combining transmission electron microscopy and dynamic light scattering. Inductively coupled plasma-atomic emission spectroscopy revealed uptake of these nanoparticles within clams and their ability to induce metallic deregulation. The results obtained indicate that Au-ZnONPs induce biochemical and histological alterations within either the digestive gland or gill tissues at high concentration. This was deduced from the significant increase in H2O2 level, superoxide dismutase and catalase activities and malondialdehyde content. Furthermore, the toxicity of Au-ZnO nanoparticles was linked with the increase of intracellular iron and calcium levels in both tissues. Histological alterations in gill and digestive gland were more pronounced with Au-ZnONP100 and this is likely related to oxidative mechanisms. Gill and digestive gland are differentially sensitive to Au-ZnONPs if the exposure concentration is higher than 50μg/L. In conclusion, the parameters considered here could constitute reliable biomarkers for evaluation of hybrid nanoparticles toxicity in environmental model organisms. In addition, based on the results obtained, gill and digestive gland of R. decussatus could be proposed as models to detect harmful effects of hybrid nanoparticles.

Effects of Gold Nanoparticles on the Mediterranean Clams Ruditapes decussatus : Chemical and Biochemical Investigations

Gold nanoparticles (Au NPs) are largely used in the medical sector as a new tool in analytical tests and drug delivery systems.

Aquatic Ecotoxicity Effects of TiO2 Nanocrystals

Aquatic Ecotoxicity Effects of TiO2 Nanocrystals A new and facile synthesis method of titanium dioxide (TiO2) nanoparticles (NPs) is presented in this work. This novel approach allows one to produce titanium dioxide nanoparticles owing to a modified solvothermal process that makes use of Titanium (IV) butoxide as the titanium precursor and Dimethyl Sulfoxide (DMSO) as a solvent. The structure and morphology of the TiO2 nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectrometry (EDX) and high-resolution transmission electron microscopy (HRTEM). Optical absorption measurement showed that the TiO2 nanoparticles exhibit a UV significant absorption peak clearly blue-shifted with respect to that of bulk TiO2. The results showed that monodisperse quasi-spherical TiO2 nanoparticles (with an average size of 11 nm) consisting of pure anatase phase were formed. To investigate the environmental impacts of the new synthesized TiO2 NPs, the oxidative stress in marine bivalves (Mytilus galloprovincialis) was assessed. No considerable effect was found in digestive gland in any of the treatment groups with TiO2 concentration gradients ranging from 0.1 to 100 mg/L. Thus, the level of the superoxide anion, the activity of an antioxidant enzyme superoxide dismutase (SOD) and the GSH/GSSG ratio showed no significantly differences in digestive gland of all treated groups compared to control. Whoever, slight modifications were observed in gill at high concentration (100 mg/L). These results demonstrated that the considered TiO2 appears to exert little toxicity on marine mussels after a short-term exposure at high concentration. The high crystalline quality, together with the easy synthesis process and limited environmental risk, makes the new TiO2 nanoparticles a promising candidate for many applications such as optoelectronics and water photolysis for hydrogen production.