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Toxicity evaluation of manufactured CeO2 nanoparticles before and after alteration: combined physicochemical and whole-genome expression analysis in Caco-2 cells.

Fisichella M, Berenguer F, Steinmetz G, Auffan M, Rose J, Prat O - BMC Genomics (2014)

Bottom Line: Gene expression profiles obtained from cells exposed to NPs before and after their alteration were compared, to highlight differences in cellular functions.No change in the cerium redox state was observed for altered NPs.Conversely, Nanobyk 3810™ coated with ammonium citrate did not display any adverse effect at the same concentration.It can be assumed that the safe design of engineered nanoparticles could include robust protective layers conferring on them greater resistance to alteration during their life cycle.

View Article: PubMed Central - PubMed

Affiliation: CEA, IBEB, SBTN, Laboratoire d'Etude des Protéines Cibles, F-30207 Bagnols-sur-Cèze, France. odette.prat@cea.fr.

ABSTRACT

Background: Engineered nanomaterials may release nanosized residues, by degradation, throughout their life cycle. These residues may be a threat for living organisms. They may be ingested by humans through food and water. Although the toxicity of pristine CeO2 nanoparticles (NPs) has been documented, there is a lack of studies on manufactured nanoparticles, which are often surface modified. Here, we investigated the potential adverse effects of CeO2 Nanobyk 3810™ NPs, used in wood care, and their residues, altered by light or acid.

Results: Human intestinal Caco-2 cells were exposed to residues degraded by daylight or in a medium simulating gastric acidity. Size and zeta potential were determined by dynamic light scattering. The surface structure and redox state of cerium were analyzed by transmission electronic microscopy (TEM) and X-ray absorption spectroscopy, respectively. Viability tests were performed in Caco-2 cells exposed to NPs. Cell morphology was imaged with scanning electronic microscopy. Gene expression profiles obtained from cells exposed to NPs before and after their alteration were compared, to highlight differences in cellular functions.No change in the cerium redox state was observed for altered NPs. All CeO2 NPs suspended in the culture medium became microsized. Cytotoxicity tests showed no toxicity after Caco-2 cell exposure to these various NPs up to 170 μg/mL (24 h and 72 h). Nevertheless, a more-sensitive whole-gene-expression study, based on a pathway-driven analysis, highlighted a modification of metabolic activity, especially mitochondrial function, by altered Nanobyk 3810™. The down-regulation of key genes of this pathway was validated by qRT-PCR. Conversely, Nanobyk 3810™ coated with ammonium citrate did not display any adverse effect at the same concentration.

Conclusion: The degraded nanoparticles were more toxic than their coated counterparts. Desorption of the outside layer was the most likely cause of this discrepancy in toxicity. It can be assumed that the safe design of engineered nanoparticles could include robust protective layers conferring on them greater resistance to alteration during their life cycle.

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SEM image and cerium characterization. Left side: SEM image, obtained in BSE mode, of Caco-2 cells exposed to Nanobyk-DL. Magnification 500 x. Right side: The EDX spectrum of the clear spots detected on the cell membrane indicates they are composed of cerium.
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Fig3: SEM image and cerium characterization. Left side: SEM image, obtained in BSE mode, of Caco-2 cells exposed to Nanobyk-DL. Magnification 500 x. Right side: The EDX spectrum of the clear spots detected on the cell membrane indicates they are composed of cerium.

Mentions: We visualized cells with SEM. Caco-2 cells exposed for 72 h to 170 μg/mL Nanobyk-type NPs did not show any alteration in density. The microvilli were also clearly visible (Additional file 2: Figure S2). These observations confirmed the absence of visible toxicity of Nanobyk NPs and indicated that, if an effect exists owing to exposure to degraded NB, this effect is small enough not to induce any drastic changes in cell morphology. It is noteworthy that this does not exclude any possible metabolic modification. Nevertheless, clear spots identified as CeO2 deposits were clearly visible on the surface of the plasma membrane, especially for NB-DL (Figure 3).Figure 3


Toxicity evaluation of manufactured CeO2 nanoparticles before and after alteration: combined physicochemical and whole-genome expression analysis in Caco-2 cells.

Fisichella M, Berenguer F, Steinmetz G, Auffan M, Rose J, Prat O - BMC Genomics (2014)

SEM image and cerium characterization. Left side: SEM image, obtained in BSE mode, of Caco-2 cells exposed to Nanobyk-DL. Magnification 500 x. Right side: The EDX spectrum of the clear spots detected on the cell membrane indicates they are composed of cerium.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC4150968&req=5

Fig3: SEM image and cerium characterization. Left side: SEM image, obtained in BSE mode, of Caco-2 cells exposed to Nanobyk-DL. Magnification 500 x. Right side: The EDX spectrum of the clear spots detected on the cell membrane indicates they are composed of cerium.
Mentions: We visualized cells with SEM. Caco-2 cells exposed for 72 h to 170 μg/mL Nanobyk-type NPs did not show any alteration in density. The microvilli were also clearly visible (Additional file 2: Figure S2). These observations confirmed the absence of visible toxicity of Nanobyk NPs and indicated that, if an effect exists owing to exposure to degraded NB, this effect is small enough not to induce any drastic changes in cell morphology. It is noteworthy that this does not exclude any possible metabolic modification. Nevertheless, clear spots identified as CeO2 deposits were clearly visible on the surface of the plasma membrane, especially for NB-DL (Figure 3).Figure 3

Bottom Line: Gene expression profiles obtained from cells exposed to NPs before and after their alteration were compared, to highlight differences in cellular functions.No change in the cerium redox state was observed for altered NPs.Conversely, Nanobyk 3810™ coated with ammonium citrate did not display any adverse effect at the same concentration.It can be assumed that the safe design of engineered nanoparticles could include robust protective layers conferring on them greater resistance to alteration during their life cycle.

View Article: PubMed Central - PubMed

Affiliation: CEA, IBEB, SBTN, Laboratoire d'Etude des Protéines Cibles, F-30207 Bagnols-sur-Cèze, France. odette.prat@cea.fr.

ABSTRACT

Background: Engineered nanomaterials may release nanosized residues, by degradation, throughout their life cycle. These residues may be a threat for living organisms. They may be ingested by humans through food and water. Although the toxicity of pristine CeO2 nanoparticles (NPs) has been documented, there is a lack of studies on manufactured nanoparticles, which are often surface modified. Here, we investigated the potential adverse effects of CeO2 Nanobyk 3810™ NPs, used in wood care, and their residues, altered by light or acid.

Results: Human intestinal Caco-2 cells were exposed to residues degraded by daylight or in a medium simulating gastric acidity. Size and zeta potential were determined by dynamic light scattering. The surface structure and redox state of cerium were analyzed by transmission electronic microscopy (TEM) and X-ray absorption spectroscopy, respectively. Viability tests were performed in Caco-2 cells exposed to NPs. Cell morphology was imaged with scanning electronic microscopy. Gene expression profiles obtained from cells exposed to NPs before and after their alteration were compared, to highlight differences in cellular functions.No change in the cerium redox state was observed for altered NPs. All CeO2 NPs suspended in the culture medium became microsized. Cytotoxicity tests showed no toxicity after Caco-2 cell exposure to these various NPs up to 170 μg/mL (24 h and 72 h). Nevertheless, a more-sensitive whole-gene-expression study, based on a pathway-driven analysis, highlighted a modification of metabolic activity, especially mitochondrial function, by altered Nanobyk 3810™. The down-regulation of key genes of this pathway was validated by qRT-PCR. Conversely, Nanobyk 3810™ coated with ammonium citrate did not display any adverse effect at the same concentration.

Conclusion: The degraded nanoparticles were more toxic than their coated counterparts. Desorption of the outside layer was the most likely cause of this discrepancy in toxicity. It can be assumed that the safe design of engineered nanoparticles could include robust protective layers conferring on them greater resistance to alteration during their life cycle.

Show MeSH
Related in: MedlinePlus