Assessing bio-available silver released from silver nanoparticles embedded in silica layers using the green algae Chlamydomonas reinhardtii as bio-sensors

Alessandro Pugliara (1, 2) , Kremena Makasheva (3) , Bernard Despax (2) , Maxime Bayle (1) , Robert Carles (1) , Patrizio Benzo (1) , Gérard Benassayag (1) , Béatrice Pécassou (1) , Maria Carmen Sancho (4) , Enrique Navarro (4) , Yolanda Echegoyen (5) , Caroline Bonafos (1)

1 CEMES - Centre d'élaboration de matériaux et d'études structurales
2 LAPLACE - LAboratoire PLasma et Conversion d'Energie
3 LAPLACE-MPP - Matériaux et Procédés Plasmas
4 IPE - CSIC - Instituto Pirenaico de Ecologìa = Pyrenean Institute of Ecology [Zaragoza]
5 University of Zaragoza - Universidad de Zaragoza [Zaragoza]

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 < 20 nm) 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 7 nm) 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 20 h of immersion in buffered water was measured by inductively coupled plasma mass spectrometry and ranges between 0.02 and 0.49 μM. 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.

Mots clés: Algae; High resolution transmission electron microscopy; Ion beams; Light transmission; Metal nanoparticles; Nanocomposites; Nanoparticles; Nanostructures; Optical properties; Plasma polymerization; Synthesis (chemical); Bio-available silver release; Chlamydomonas reinhardtii; Physical synthesis; Silica matrix; Silver nanoparticles; nanocomposite; silver; silver nanoparticle; bioavailability; green alga; nanoparticle; photosynthesis; sensor; silica; toxicity; Article; concentration (parameters); controlled study; ecotoxicity; fluorometry; mass spectrometry; nonhuman; particle size; priority journal; structure analysis; transmission electron microscopy; algae; Chlorophyta

Domaines: Physique [physics]

Alessandro Pugliara, Kremena Makasheva, Bernard Despax, Maxime Bayle, Robert Carles, et al.. Assessing bio-available silver released from silver nanoparticles embedded in silica layers using the green algae Chlamydomonas reinhardtii as bio-sensors. Science of the Total Environment, 2015, 565, pp.863-871. ⟨10.1016/j.scitotenv.2016.02.141⟩. ⟨hal-01718633⟩