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Is the toxic potential of nanosilver dependent on its size?

Huk A, Izak-Nau E, Reidy B, Boyles M, Duschl A, Lynch I, Dušinska M - Part Fibre Toxicol (2014)

Bottom Line: However, re-calculation of Ag ENMs concentrations from mass unit to surface area and number of ENMs per cm2 highlighted that 200 nm Ag ENMs, are the most toxic.Strong cytotoxic and genotoxic effects were observed in cells exposed to Ag ENMs 50 nm, but Ag ENMs 200 nm had the most mutagenic potential.Additionally, we showed that expression of concentrations of ENMs in mass units is not representative.

View Article: PubMed Central - PubMed

ABSTRACT

Background: Nanosilver is one of the most commonly used engineered nanomaterials (ENMs). In our study we focused on assessing the size-dependence of the toxicity of nanosilver (Ag ENMs), utilising materials of three sizes (50, 80 and 200 nm) synthesized by the same method, with the same chemical composition, charge and coating.

Methods: Uptake and localisation (by Transmission Electron Microscopy), cell proliferation (Relative growth activity) and cytotoxic effects (Plating efficiency), inflammatory response (induction of IL-8 and MCP-1 by Enzyme linked immune sorbent assay), DNA damage (strand breaks and oxidised DNA lesions by the Comet assay) were all assessed in human lung carcinoma epithelial cells (A549), and the mutagenic potential of ENMs (Mammalian hprt gene mutation test) was assessed in V79-4 cells as per the OECD protocol. Detailed physico-chemical characterization of the ENMs was performed in water and in biological media as a prerequisite to assessment of their impacts on cells. To study the relationship between the surface area of the ENMs and the number of ENMs with the biological response observed, Ag ENMs concentrations were recalculated from μg/cm2 to ENMs cm2/cm2 and ENMs/cm2.

Results: Studied Ag ENMs are cytotoxic and cytostatic, and induced strand breaks, DNA oxidation, inflammation and gene mutations. Results expressed in mass unit [μg/cm2] suggested that the toxicity of Ag ENMs is size dependent with 50 nm being most toxic. However, re-calculation of Ag ENMs concentrations from mass unit to surface area and number of ENMs per cm2 highlighted that 200 nm Ag ENMs, are the most toxic. Results from hprt gene mutation assay showed that Ag ENMs 200 nm are the most mutagenic irrespective of the concentration unit expressed.

Conclusion: We found that the toxicity of Ag ENMs is not always size dependent. Strong cytotoxic and genotoxic effects were observed in cells exposed to Ag ENMs 50 nm, but Ag ENMs 200 nm had the most mutagenic potential. Additionally, we showed that expression of concentrations of ENMs in mass units is not representative. Number of ENMs or surface area of ENMs (per cm2) seem more precise units with which to compare the toxicity of different ENMs.

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Related in: MedlinePlus

TEM characterization of pristine Ag ENMs: (A) Ag ENMs 200 nm, (B) Ag ENMs 80 nm, (C) Ag ENMs 50 nm; scale bar: 1 μm.
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Fig1: TEM characterization of pristine Ag ENMs: (A) Ag ENMs 200 nm, (B) Ag ENMs 80 nm, (C) Ag ENMs 50 nm; scale bar: 1 μm.

Mentions: PVP-stabilized Ag ENMs were produced with the desired sizes (50, 80, 200 nm). The results of the ENM characterization in water (as synthesised) are summarized in Table 1. SEM and TEM images show a quasi-spherical shape and good monodispersity of the ENMs (Figure 1, Additional file 1: Figure S1, Additional file 2: Figure S2 and Additional file 3: Figure S3). The monodispersity was additionally proven by DLS (Table 1) and analytical centrifugation (AC) measurements (Additional files 1, 2 and 3). The XRD spectra show the crystalline nature of the Ag ENM. The presence of PVP immobilized onto the ENMs surface was indicated by XPS and SIMS analysis. XPS data also demonstrated that all surface atoms are in the Ag0 state, confirming the absence of Ag ions at this time point. (Additional file 1: Figure S1, Additional file 2: Figure S2 and Additional file 3: Figure S3).Table 1


Is the toxic potential of nanosilver dependent on its size?

Huk A, Izak-Nau E, Reidy B, Boyles M, Duschl A, Lynch I, Dušinska M - Part Fibre Toxicol (2014)

TEM characterization of pristine Ag ENMs: (A) Ag ENMs 200 nm, (B) Ag ENMs 80 nm, (C) Ag ENMs 50 nm; scale bar: 1 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4274708&req=5

Fig1: TEM characterization of pristine Ag ENMs: (A) Ag ENMs 200 nm, (B) Ag ENMs 80 nm, (C) Ag ENMs 50 nm; scale bar: 1 μm.
Mentions: PVP-stabilized Ag ENMs were produced with the desired sizes (50, 80, 200 nm). The results of the ENM characterization in water (as synthesised) are summarized in Table 1. SEM and TEM images show a quasi-spherical shape and good monodispersity of the ENMs (Figure 1, Additional file 1: Figure S1, Additional file 2: Figure S2 and Additional file 3: Figure S3). The monodispersity was additionally proven by DLS (Table 1) and analytical centrifugation (AC) measurements (Additional files 1, 2 and 3). The XRD spectra show the crystalline nature of the Ag ENM. The presence of PVP immobilized onto the ENMs surface was indicated by XPS and SIMS analysis. XPS data also demonstrated that all surface atoms are in the Ag0 state, confirming the absence of Ag ions at this time point. (Additional file 1: Figure S1, Additional file 2: Figure S2 and Additional file 3: Figure S3).Table 1

Bottom Line: However, re-calculation of Ag ENMs concentrations from mass unit to surface area and number of ENMs per cm2 highlighted that 200 nm Ag ENMs, are the most toxic.Strong cytotoxic and genotoxic effects were observed in cells exposed to Ag ENMs 50 nm, but Ag ENMs 200 nm had the most mutagenic potential.Additionally, we showed that expression of concentrations of ENMs in mass units is not representative.

View Article: PubMed Central - PubMed

ABSTRACT

Background: Nanosilver is one of the most commonly used engineered nanomaterials (ENMs). In our study we focused on assessing the size-dependence of the toxicity of nanosilver (Ag ENMs), utilising materials of three sizes (50, 80 and 200 nm) synthesized by the same method, with the same chemical composition, charge and coating.

Methods: Uptake and localisation (by Transmission Electron Microscopy), cell proliferation (Relative growth activity) and cytotoxic effects (Plating efficiency), inflammatory response (induction of IL-8 and MCP-1 by Enzyme linked immune sorbent assay), DNA damage (strand breaks and oxidised DNA lesions by the Comet assay) were all assessed in human lung carcinoma epithelial cells (A549), and the mutagenic potential of ENMs (Mammalian hprt gene mutation test) was assessed in V79-4 cells as per the OECD protocol. Detailed physico-chemical characterization of the ENMs was performed in water and in biological media as a prerequisite to assessment of their impacts on cells. To study the relationship between the surface area of the ENMs and the number of ENMs with the biological response observed, Ag ENMs concentrations were recalculated from μg/cm2 to ENMs cm2/cm2 and ENMs/cm2.

Results: Studied Ag ENMs are cytotoxic and cytostatic, and induced strand breaks, DNA oxidation, inflammation and gene mutations. Results expressed in mass unit [μg/cm2] suggested that the toxicity of Ag ENMs is size dependent with 50 nm being most toxic. However, re-calculation of Ag ENMs concentrations from mass unit to surface area and number of ENMs per cm2 highlighted that 200 nm Ag ENMs, are the most toxic. Results from hprt gene mutation assay showed that Ag ENMs 200 nm are the most mutagenic irrespective of the concentration unit expressed.

Conclusion: We found that the toxicity of Ag ENMs is not always size dependent. Strong cytotoxic and genotoxic effects were observed in cells exposed to Ag ENMs 50 nm, but Ag ENMs 200 nm had the most mutagenic potential. Additionally, we showed that expression of concentrations of ENMs in mass units is not representative. Number of ENMs or surface area of ENMs (per cm2) seem more precise units with which to compare the toxicity of different ENMs.

Show MeSH
Related in: MedlinePlus