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Mechanisms of Toxicity of Ag Nanoparticles in Comparison to Bulk and Ionic Ag on Mussel Hemocytes and Gill Cells.

Katsumiti A, Gilliland D, Arostegui I, Cajaraville MP - PLoS ONE (2015)

Bottom Line: Maltose alone provoked minor effects on cell viability.Similar effects were observed after exposure to ionic and bulk Ag in the two cell types, although generally effects were more marked for the ionic form.In conclusion, results suggest that most observed responses were due at least in part to dissolved Ag.

View Article: PubMed Central - PubMed

Affiliation: CBET Research Group, Department of Zoology and Animal Cell Biology, Faculty of Science and Technology and Research Centre for Experimental Marine Biology and Biotechnology PIE, University of the Basque Country UPV/EHU, Plentzia, Spain.

ABSTRACT
Silver nanoparticles (Ag NPs) are increasingly used in many products and are expected to end up in the aquatic environment. Mussels have been proposed as marine model species to evaluate NP toxicity in vitro. The objective of this work was to assess the mechanisms of toxicity of Ag NPs on mussel hemocytes and gill cells, in comparison to ionic and bulk Ag. Firstly, cytotoxicity of commercial and maltose stabilized Ag NPs was screened in parallel with the ionic and bulk forms at a wide range of concentrations in isolated mussel cells using cell viability assays. Toxicity of maltose alone was also tested. LC50 values were calculated and the most toxic Ag NPs tested were selected for a second step where sublethal concentrations of each Ag form were tested using a wide array of mechanistic tests in both cell types. Maltose-stabilized Ag NPs showed size-dependent cytotoxicity, smaller (20 nm) NPs being more toxic than larger (40 and 100 nm) NPs. Maltose alone provoked minor effects on cell viability. Ionic Ag was the most cytotoxic Ag form tested whereas bulk Ag showed similar cytotoxicity to the commercial Ag NPs. Main mechanisms of action of Ag NPs involved oxidative stress and genotoxicity in the two cell types, activation of lysosomal AcP activity, disruption of actin cytoskeleton and stimulation of phagocytosis in hemocytes and increase of MXR transport activity and inhibition of Na-K-ATPase in gill cells. Similar effects were observed after exposure to ionic and bulk Ag in the two cell types, although generally effects were more marked for the ionic form. In conclusion, results suggest that most observed responses were due at least in part to dissolved Ag.

No MeSH data available.


Related in: MedlinePlus

DLS patterns of size distribution of the maltose-stabilized Ag NPs.Ag20-Mal (1), Ag40-Mal (2) and Ag100-Mal (3) NPs in distilled water. d.nm = diameter in nm.
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pone.0129039.g002: DLS patterns of size distribution of the maltose-stabilized Ag NPs.Ag20-Mal (1), Ag40-Mal (2) and Ag100-Mal (3) NPs in distilled water. d.nm = diameter in nm.

Mentions: According to the SEM analysis, Ag20-Mal, Ag40-Mal and Ag100-Mal samples correspond to spherical NPs of roughly 20, 40 and 100 nm (Fig 1A–1C). The absorption wavelength peaks of maltose-stabilized Ag NPs (Fig 1D) were consistent with NPs of the size diameters observed in the SEM analysis. DLS analysis showed that maltose-stabilized Ag NPs of the three sizes were monodispersed NPs (Fig 2), with negative zeta potential values ranging from -30 to -35 mV, which correspond to colloidally stable samples. TEM analysis of the commercial Ag20 and Ag80 NPs showed that both samples contain spherical (below 10 nm) and larger polydispersed NPs of roughly 20 and 80 nm respectively besides of some aggregated NPs (Fig 3A–3D). TEM images of bulk Ag showed that sample contains larger amorphous Ag particles over 2 μm in size (Fig 3E and 3F). Ag20 NPs, Ag80 NPs and bulk Ag showed high zeta potential values (-50±0.5, -44±1, -68±3 mV respectively) that correspond to stable electrostatically stabilized particles in dispersions. Dissolution of maltose stabilized Ag NPs in SW was detected after less than 1 h of experimentation (Table 1). The release of silver ions was rapid and continuous. During the first 24 h, Ag20-Mal NPs tended to dissolve faster than the other two maltose stabilized Ag NPs (Table 1). At 24 h, 11.7% of the total Ag20-Mal NPs was converted into ionic Ag when only 8.7 and 7.2% of Ag40-Mal and Ag100-Mal respectively were ionized (Table 1). More than 20% of the metallic silver was converted into ionic form at 168 h in SW (Table 1).


Mechanisms of Toxicity of Ag Nanoparticles in Comparison to Bulk and Ionic Ag on Mussel Hemocytes and Gill Cells.

Katsumiti A, Gilliland D, Arostegui I, Cajaraville MP - PLoS ONE (2015)

DLS patterns of size distribution of the maltose-stabilized Ag NPs.Ag20-Mal (1), Ag40-Mal (2) and Ag100-Mal (3) NPs in distilled water. d.nm = diameter in nm.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4465040&req=5

pone.0129039.g002: DLS patterns of size distribution of the maltose-stabilized Ag NPs.Ag20-Mal (1), Ag40-Mal (2) and Ag100-Mal (3) NPs in distilled water. d.nm = diameter in nm.
Mentions: According to the SEM analysis, Ag20-Mal, Ag40-Mal and Ag100-Mal samples correspond to spherical NPs of roughly 20, 40 and 100 nm (Fig 1A–1C). The absorption wavelength peaks of maltose-stabilized Ag NPs (Fig 1D) were consistent with NPs of the size diameters observed in the SEM analysis. DLS analysis showed that maltose-stabilized Ag NPs of the three sizes were monodispersed NPs (Fig 2), with negative zeta potential values ranging from -30 to -35 mV, which correspond to colloidally stable samples. TEM analysis of the commercial Ag20 and Ag80 NPs showed that both samples contain spherical (below 10 nm) and larger polydispersed NPs of roughly 20 and 80 nm respectively besides of some aggregated NPs (Fig 3A–3D). TEM images of bulk Ag showed that sample contains larger amorphous Ag particles over 2 μm in size (Fig 3E and 3F). Ag20 NPs, Ag80 NPs and bulk Ag showed high zeta potential values (-50±0.5, -44±1, -68±3 mV respectively) that correspond to stable electrostatically stabilized particles in dispersions. Dissolution of maltose stabilized Ag NPs in SW was detected after less than 1 h of experimentation (Table 1). The release of silver ions was rapid and continuous. During the first 24 h, Ag20-Mal NPs tended to dissolve faster than the other two maltose stabilized Ag NPs (Table 1). At 24 h, 11.7% of the total Ag20-Mal NPs was converted into ionic Ag when only 8.7 and 7.2% of Ag40-Mal and Ag100-Mal respectively were ionized (Table 1). More than 20% of the metallic silver was converted into ionic form at 168 h in SW (Table 1).

Bottom Line: Maltose alone provoked minor effects on cell viability.Similar effects were observed after exposure to ionic and bulk Ag in the two cell types, although generally effects were more marked for the ionic form.In conclusion, results suggest that most observed responses were due at least in part to dissolved Ag.

View Article: PubMed Central - PubMed

Affiliation: CBET Research Group, Department of Zoology and Animal Cell Biology, Faculty of Science and Technology and Research Centre for Experimental Marine Biology and Biotechnology PIE, University of the Basque Country UPV/EHU, Plentzia, Spain.

ABSTRACT
Silver nanoparticles (Ag NPs) are increasingly used in many products and are expected to end up in the aquatic environment. Mussels have been proposed as marine model species to evaluate NP toxicity in vitro. The objective of this work was to assess the mechanisms of toxicity of Ag NPs on mussel hemocytes and gill cells, in comparison to ionic and bulk Ag. Firstly, cytotoxicity of commercial and maltose stabilized Ag NPs was screened in parallel with the ionic and bulk forms at a wide range of concentrations in isolated mussel cells using cell viability assays. Toxicity of maltose alone was also tested. LC50 values were calculated and the most toxic Ag NPs tested were selected for a second step where sublethal concentrations of each Ag form were tested using a wide array of mechanistic tests in both cell types. Maltose-stabilized Ag NPs showed size-dependent cytotoxicity, smaller (20 nm) NPs being more toxic than larger (40 and 100 nm) NPs. Maltose alone provoked minor effects on cell viability. Ionic Ag was the most cytotoxic Ag form tested whereas bulk Ag showed similar cytotoxicity to the commercial Ag NPs. Main mechanisms of action of Ag NPs involved oxidative stress and genotoxicity in the two cell types, activation of lysosomal AcP activity, disruption of actin cytoskeleton and stimulation of phagocytosis in hemocytes and increase of MXR transport activity and inhibition of Na-K-ATPase in gill cells. Similar effects were observed after exposure to ionic and bulk Ag in the two cell types, although generally effects were more marked for the ionic form. In conclusion, results suggest that most observed responses were due at least in part to dissolved Ag.

No MeSH data available.


Related in: MedlinePlus