title: Assessing bio-available silver released from silver nanoparticles embedded in silica layers using the green algae Chlamydomonas reinhardtii as bio-sensors.
abstract: Silver nanoparticles (AgNPs) because of their strong antibacterial activity are widely used in health-care sector and industrial applications. Their huge surface-volume ratio enhances the silver release compared to the bulk material, leading to an increased toxicity for microorganisms sensitive to this element. This work presents an assessment of the toxic effect on algal photosynthesis due to small (size <20nm) AgNPs embedded in silica layers. Two physical approaches were originally used to elaborate the nanocomposite structures: (i) low energy ion beam synthesis and (ii) combined silver sputtering and plasma polymerization. These techniques allow elaboration of a single layer of AgNPs embedded in silica films at defined nanometer distances (from 0 to 7nm) beneath the free surface. The structural and optical properties of the nanostructures were studied by transmission electron microscopy and optical reflectance. The silver release from the nanostructures after 20h of immersion in buffered water was measured by inductively coupled plasma mass spectrometry and ranges between 0.02 and 0.49μM. The short-term toxicity of Ag to photosynthesis of Chlamydomonas reinhardtii was assessed by fluorometry. The obtained results show that embedding AgNPs reduces the interactions with the buffered water free media, protecting the AgNPs from fast oxidation. The release of bio-available silver (impacting on the algal photosynthesis) is controlled by the depth at which AgNPs are located for a given host matrix. This provides a procedure to tailor the toxicity of nanocomposites containing AgNPs.
authors.affiliation: nMat group-CEMES (Centre d'Elaboration de Matériaux et d'Etudes Structurales)-CNRS, Université de Toulouse, 29 rue Jeanne Marvig, BP 94347, F-31055 Toulouse Cedex 4, France; LAPLACE (LAboratoire PLAsma et Conversion d'Energie), Université de Toulouse, CNRS, UPS, INPT, 118 route de Narbonne, F-31062 Toulouse, France.
authors.forename: Alessandro
authors.initials: A
authors.lastname: Pugliara
authors.affiliation: LAPLACE (LAboratoire PLAsma et Conversion d'Energie), Université de Toulouse, CNRS, UPS, INPT, 118 route de Narbonne, F-31062 Toulouse, France.
authors.forename: Kremena
authors.initials: K
authors.lastname: Makasheva
authors.affiliation: LAPLACE (LAboratoire PLAsma et Conversion d'Energie), Université de Toulouse, CNRS, UPS, INPT, 118 route de Narbonne, F-31062 Toulouse, France.
authors.forename: Bernard
authors.initials: B
authors.lastname: Despax
authors.affiliation: nMat group-CEMES (Centre d'Elaboration de Matériaux et d'Etudes Structurales)-CNRS, Université de Toulouse, 29 rue Jeanne Marvig, BP 94347, F-31055 Toulouse Cedex 4, France.
authors.forename: Maxime
authors.initials: M
authors.lastname: Bayle
authors.affiliation: nMat group-CEMES (Centre d'Elaboration de Matériaux et d'Etudes Structurales)-CNRS, Université de Toulouse, 29 rue Jeanne Marvig, BP 94347, F-31055 Toulouse Cedex 4, France.
authors.forename: Robert
authors.initials: R
authors.lastname: Carles
authors.affiliation: nMat group-CEMES (Centre d'Elaboration de Matériaux et d'Etudes Structurales)-CNRS, Université de Toulouse, 29 rue Jeanne Marvig, BP 94347, F-31055 Toulouse Cedex 4, France.
authors.forename: Patrizio
authors.initials: P
authors.lastname: Benzo
authors.affiliation: nMat group-CEMES (Centre d'Elaboration de Matériaux et d'Etudes Structurales)-CNRS, Université de Toulouse, 29 rue Jeanne Marvig, BP 94347, F-31055 Toulouse Cedex 4, France.
authors.forename: Gérard
authors.initials: G
authors.lastname: BenAssayag
authors.affiliation: nMat group-CEMES (Centre d'Elaboration de Matériaux et d'Etudes Structurales)-CNRS, Université de Toulouse, 29 rue Jeanne Marvig, BP 94347, F-31055 Toulouse Cedex 4, France.
authors.forename: Béatrice
authors.initials: B
authors.lastname: Pécassou
authors.affiliation: IPE (Instituto Pirenaico de Ecología)-CSIC, Avda. Montañana 1005, Zaragoza 50059, Spain.
authors.forename: Maria Carmen
authors.initials: MC
authors.lastname: Sancho
authors.affiliation: IPE (Instituto Pirenaico de Ecología)-CSIC, Avda. Montañana 1005, Zaragoza 50059, Spain.
authors.forename: Enrique
authors.initials: E
authors.lastname: Navarro
authors.affiliation: I3A, Department of Analytical Chemistry, University of Zaragoza, C/ María de Luna 3, 50018, Zaragoza, Spain.
authors.forename: Yolanda
authors.initials: Y
authors.lastname: Echegoyen
authors.affiliation: nMat group-CEMES (Centre d'Elaboration de Matériaux et d'Etudes Structurales)-CNRS, Université de Toulouse, 29 rue Jeanne Marvig, BP 94347, F-31055 Toulouse Cedex 4, France. Electronic address: bonafos@cemes.fr.
authors.forename: Caroline
authors.initials: C
authors.lastname: Bonafos
mesh_terms: D000900:Anti-Bacterial Agents / Q000633:toxicity*; D016825:Chlamydomonas reinhardtii / Q000187:drug effects*; D004784:Environmental Monitoring / Q000379:methods*; D053768:Metal Nanoparticles / Q000633:toxicity*; D012822:Silicon Dioxide / Q000737:chemistry; D012834:Silver / Q000633:toxicity*; D014874:Water Pollutants, Chemical / Q000633:toxicity*
chemical_list: D000900:Anti-Bacterial Agents; D014874:Water Pollutants, Chemical; D012834:Silver; D012822:Silicon Dioxide
keywords: Bio-available silver release; Chlamydomonas reinhardtii; Embedded silver nanoparticles; Host silica matrix; Physical synthesis; Toxicity