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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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Related in: MedlinePlus

Radar plots of gene distribution per altered function. Genes significantly induced or repressed after exposure to NPs were selected as described in Table 1, Column 4. Genes were selected with fold-change ratios greater than 1.5 (n = 4, p-value ≤ 0.05), and distributed per function. This graph displays the number of significantly altered genes per function. The enlarged part concerns light-degraded Nanobyk (NB-DL) and acid-degraded Nanobyk (NB-DA). For each compound, a pattern is obtained representing the amplitude and the nature of its toxicity, then allowing a visual comparison of their respective toxicities.
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Fig4: Radar plots of gene distribution per altered function. Genes significantly induced or repressed after exposure to NPs were selected as described in Table 1, Column 4. Genes were selected with fold-change ratios greater than 1.5 (n = 4, p-value ≤ 0.05), and distributed per function. This graph displays the number of significantly altered genes per function. The enlarged part concerns light-degraded Nanobyk (NB-DL) and acid-degraded Nanobyk (NB-DA). For each compound, a pattern is obtained representing the amplitude and the nature of its toxicity, then allowing a visual comparison of their respective toxicities.

Mentions: For pristine CeO2 NPs, the main altered functions were cellular growth and proliferation (274 genes) and cell death (265 genes), as shown in Figure 4. Contrarily to pristine CeO2 NPs, the surface-treated NB NPs did not alter any specific cellular function (not shown in Figure 4, as only 13 genes are altered), thus proving the efficiency of the protective triammonium citrate layer. The NB nanoparticle residues of degradation by light or acid altered similar functions to pristine CeO2 NPs, although in a very moderate way, given the number of altered genes. The distribution per function for NB residues is shown in the enlarged part of Figure 4. For NB-DL, the main altered functions were cellular growth and proliferation (51 genes), cellular development (35 genes), small molecule biochemistry (26 genes), cellular assembly and organization (25 genes), cell cycle (24 genes), cellular function and maintenance (24 genes) and cell death (20 genes). Other functions counted for less than 15 genes each.Figure 4


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)

Radar plots of gene distribution per altered function. Genes significantly induced or repressed after exposure to NPs were selected as described in Table 1, Column 4. Genes were selected with fold-change ratios greater than 1.5 (n = 4, p-value ≤ 0.05), and distributed per function. This graph displays the number of significantly altered genes per function. The enlarged part concerns light-degraded Nanobyk (NB-DL) and acid-degraded Nanobyk (NB-DA). For each compound, a pattern is obtained representing the amplitude and the nature of its toxicity, then allowing a visual comparison of their respective toxicities.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Fig4: Radar plots of gene distribution per altered function. Genes significantly induced or repressed after exposure to NPs were selected as described in Table 1, Column 4. Genes were selected with fold-change ratios greater than 1.5 (n = 4, p-value ≤ 0.05), and distributed per function. This graph displays the number of significantly altered genes per function. The enlarged part concerns light-degraded Nanobyk (NB-DL) and acid-degraded Nanobyk (NB-DA). For each compound, a pattern is obtained representing the amplitude and the nature of its toxicity, then allowing a visual comparison of their respective toxicities.
Mentions: For pristine CeO2 NPs, the main altered functions were cellular growth and proliferation (274 genes) and cell death (265 genes), as shown in Figure 4. Contrarily to pristine CeO2 NPs, the surface-treated NB NPs did not alter any specific cellular function (not shown in Figure 4, as only 13 genes are altered), thus proving the efficiency of the protective triammonium citrate layer. The NB nanoparticle residues of degradation by light or acid altered similar functions to pristine CeO2 NPs, although in a very moderate way, given the number of altered genes. The distribution per function for NB residues is shown in the enlarged part of Figure 4. For NB-DL, the main altered functions were cellular growth and proliferation (51 genes), cellular development (35 genes), small molecule biochemistry (26 genes), cellular assembly and organization (25 genes), cell cycle (24 genes), cellular function and maintenance (24 genes) and cell death (20 genes). Other functions counted for less than 15 genes each.Figure 4

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