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