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Table 1 Studies addressing the effects of different NPs on viability of gastro-intestinal cellular models

From: The unrecognized occupational relevance of the interaction between engineered nanomaterials and the gastro-intestinal tract: a consensus paper from a multidisciplinary working group

Nanoparticles Physico-chemical NP properties Cell line Experimental design Cytotoxic effects Reference
SW-CNTs Surface functionalization: SW-CNTs modified with COOH-functional groups. SW480 Up to 24 h exposure to CNTs (0.5–2 μg per well) After 4 and 24 h of exposure, CNTs did not have any cytotoxic effect, however there was a reduction in viability at 48 h and for the highest dose employed. Kulamarva et al. 2008 [58]
CdSe- QDs; CdSe-ZnS-PEG coated QDs Surface characterization: ZnS shell and poly-ethylene glycol hydrophilic coating. Caco-2 Twenty four h exposure to native QDs or QDs incubated acidic medium (0–105 nmol/ml) A dose dependent cytotoxicity for CdSe-QDs was detected. Toxic effects increased with increasing the Cd/Se ratio during synthesis.
PEG-coated QDs had less effects.
The relative viability of Caco-2 cells dropped from 90% when incubating with 4.2 nmol/ml CdSe-ZnS-PEG-QDs to 53% when incubating with acid medium treated QDs. This result was not confirmed for CdSe- QDs incubated into acid medium.
Wang et al. 2008 [67]
Au-nanorods CTAB capped and PAA and PAH-coated Au-nanorods. HT-29 Four days exposure to Au-nanorods (0.4 nM) CTAB-capped Au-nanorods displayed a significant cytotoxicity (65–75% loss of viability), independent of the aspect ratio.
PAA- and PAH-coated gold nanorod solutions were found relatively nontoxic
Alkilany et al. 2009 [49]
SW- CNTs Size: average diameter of individual SW-CNT is 1.4 ± 0.1 nm, bundle dimensions are 4–5 nm × 0.5–1.5 μm
Surface functionalization: carboxylic acid.
Caco-2 Twenty-four h exposure to CNTs (5 and 1000 μg/ml) A significant decrease in cell viability was detected at the higher concentrations: 500 and 1000 μg/ml. Jos et al. 2009 [57]
MW-CNTs Impurities: traces of cobalt, nickel, zinc and lead Caco-2 Seventy-two h exposure to MW-CNTs (0–100 μg/ml) No significant difference in CFE dose-effect relationship in comparison to controls. Ponti et al. 2010 [65]
ZnO-NPs Size: 50–70 nm;
Average diameter: 196 nm;
Surface area: 3 m2/g.
Lovo Up to 72 h exposure to ZnO, (0–23 μg/ml) ZnO-NPs induced a time- and dose-dependent decrease of cell number. Ten, 20 and 40 μg/cm2 induced <5% cell survival after 24 h.
Dose-dependent apoptotic cell death was evident.
De Berardis et al. 2010 [42]
TiO2-NPs Size: <40 nm;
Crystal form: a mixture of rutile and anatase;
Surface area: 20–40 m2/g;
Hydrodynamic diameter (water): 220 ± 20 nm.
Caco-2 Twenty-four h, or 10 days chronic exposure to TiO2-NPs (0–1000 μg/ml) Little indication of any cell fatality compared to the controls was reported at both time points for all concentrations employed. Koeneman et al. 2010 [32]
Ag-NPs Caco-2 Twenty-four h exposure to Ag-NPs (0–10 μg/ml) At 1 μg/ml cells did not show a significant viability decrease (LD50: ~5 μg Ag/ml). Lamb et al. 2010 [62]
Ag-NPs Size (mean ± SD): 20 ± 2–113 ± 8 nm;
Hydrodinamic diameter (mean ± SD):
- MQ water (24 h followed by sonication): 94 ± 4–177 ± 8 nm;
- DMEM (24 h followed by sonication): 118 ± 8–189 ± 9;
Impurities in NP suspensions: none.
Elementary Ag + in supernatant: 17.4; 15.8; 5.8; and 7.6% for 20, 34, 61, 113 nm NPs, respectively
Caco-2 and Raji B cells in co-culture Twenty-four h exposure to Ag-NPs (0–50 μg/ml) No significant viability alterations were observed. Bouwmeester et al. 2011 [61]
Fe2O3, TiO2, SiO2, and ZnO nano-powders Size: 3, 5, 10 and 8–10 for Fe2O3, TiO2, SiO2, and ZnO- NPs, respectively.
Agglomerate mode (DMEM culture media): 1300, 1000, 600, 650 nm, respectively.
Surface area: 222, 240, 124, 24 m2/g, respectively.
Caco-2 and RKO Twenty-four h exposure to SiO2, TiO2, ZnO and Fe2O3 nano- powders (0–100 μg/cm2) in the presence or absence of TNF-α. TiO2, SiO2, and Fe2O3 had minimal toxicity below 100 μg/cm2.
ZnO displayed the most relevant toxicity (LC50 27 ± 3.6 and 28 ± 4.6 μg/cm2 for RKO and Caco-2, respectively).
TNF-α pretreatment did not induce differences in cell viability.
Moos et al. 2011 [41]
Fullerenes; SW-CNTs Surface functionalization: polyhydroxy small-gap fullerenes (OH-fullerenes), COOH-SW-CNTs; PEG-SW-CNTs.
Size: 0.7 (fullerenes); 1.4 ± 0.1 nm in diameter, 4–5 nm × 0.5–1.5 μm bundle dimension (COOH-SW-CNTs); 1.4 ± 0.1 nm in diameter, 4–5 nm × 0.5–0.6 μm in bundle dimension (PEG-SW-CNTs).
Purity: >90% (COOH-SW-CNTs); >80% (PEG-SW-CNTs).
Caco-2 cells Twenty-four h exposure to carbon nanomaterials (0–1000 μg/ml) All three carbon nanomaterials had minimum cytotoxicity on Caco-2 cells (range of 15.6–1000 μg/mL),
and no significant difference was observed compared to the vehicle control.
Coyuco et al. 2011 [37]
Ag-NPs Size: 20, 40 nm;
Surface coating: peptide L-cysteine L-lysine L-lysine
Caco-2 Up to 48 h exposure to Ag-NPs (0–100 μg/ml). Time-, concentration- and particle size-dependent decrease in cell viability. More toxic effects for 20 nm compared to 40 nm sized Ag-NPs. Böhmert et al. 2012 [141]
Size: 14 and <10 nm for SiO2- and ZnO-NPs, respectively;
Surface area: 200 and ≥70 m2/g for SiO2- and ZnO-NPs, respectively;
Shape: near-spherical and needle-like ZnO-NPs; Spherical SiO2-NPs
Caco-2 Up to 24 h exposure to 0–80 μg/cm2 native or digestion simulated (DS) SiO2-, and ZnO-NPs. SiO2-NPs and DS- SiO2-NPs reduced cell viability only in undifferentiated Caco-2 cells (even at 5 μg/cm2).
ZnO-NPs and DS-ZnO-NPs were cytotoxic to both undifferentiated and differentiated cells (24 h)
Gerloff et al. 2013 [45]
TiO2-surface treated NPs T-light SF NPs, a rutile core surrounded by an Al hydroxide layer, vs degradation residues generated after exposure to UV light (T light-DL) or acidic medium (T light-DA).
Rutile core size: 7 ± 2 nm × 50 ± 10 nm)
Hydrodynamic diameter: T light (347 ± 69); T light-DA (688 ± 209 nm); T light-DL (237 ± 26 nm).
Caco-2 Up to 72 h exposure to TiO2-surface treated NPs (0–100 μg/ml) No cytotoxic effects were reported using Tripan blue, ATP, XTT and assays Fisichella et al. 2012 [33]
ZnO- NPs;
Size: 50–70 nm for ZnO-NPs and <25 nm for anatase TiO2-NPs.
Purity: 99.7% for TiO2-NPs.
Mean hydrodynamic diameter in ethanol and serum-free culture medium, respectively: 340.2 ± 12.04, 941.6 ± 118.3 nm for ZnO-NPs; 771.9 ± 110 and 1080 ± 190.5 nm for TiO2-NPs.
Shape: spherules to rod-like or irregularly shaped particles.
Impurities: 0.47% of Cu and traces of Ni, and Pb in ZnO-NPs; 4.0%
of Sc, 0.6% of Sb and 0.5% of B in TiO2-NPs.
Caco-2 Six and 24 h exposure to ZnO, and TiO2-NPs (0–140 μg/ml) with or without inactivated foetal calf serum. A dose-dependent decrease of cell viability after ZnO-NP exposure.
The presence of the foetal calf serum strongly reduced ZnO NP toxic effects.
No effect on cell viability was reported after treatment with TiO2-NPs either in presence or in absence of foetal calf serum.
De Angelis et al. 2013 [40]
Size: 20–30, 21, 20 for Ag, TiO2, and ZnO-NPs, respectively;
Purity: >99.5% for all NPs;
Specific surface area: ~20, 50 ± 15, 50 m2/g for Ag, TiO2, and ZnO-NPs, respectively.
Size in Caco-2 media: 202–227, 311–305, and 212–260 nm for Ag, TiO2, and ZnO-NPs, respectively.
Size in SW480 media: 207–221, 306–300, and 288–303 nm, respectively.
Caco-2 and SW480 Up to 48 h exposure to Ag, TiO2, and ZnO-NPs (0–100 μg/ml). ZnO-NPs (10 and 100 μg/ml) were cytotoxic to both cell lines at 24 and 48 h exposure.
No alterations were induced by Ag- and TiO2-NPs.
Abbot and Schwab, 2013 [39]
TiO2- nanobelts;
TiO2 anatase nanobelts size: length (7 μm), width (0.2 μm), thickness (0.01 μm);
Hydrodynamic size (water): 2897 ± 117 nm;
Surface area: 17.94 m2/g.
MW-CNTs size: length (5–10 nm), diameter (20–30 nm).
Hydrodynamic size (water): 858 ± 58 nm.
Surface area: 513 m2/g;
Impurities: 1.8% Ni and 0.1% Fe.
Caco-2/HT29-MTX co-culture One and 24 h exposure to TiO2- nanobelts;
MW-CNTs (10 and 100 μg/ml)
TiO2-nanobelts: only low levels of toxicity were observed.
MW-CNTs: no toxicity at 1 h post exposure, and a low level of toxicity (<20% compared to controls) at 24 h post exposure (only for 100 μg/ml).
Tilton et al. 2014 [51]
TiO2-NPs Size: 21 nm (P25 Degussa); 10–25 nm (anatase); 30 nm (rutile);
Hydrodynamic diameter (Milliq water): 7.1 ± 4.1, 42.3 ± 14.4 and 88.3 ± 34.1 nm for P25, anatase and rutile, respectively.
Caco-2 Twenty-four h exposure to TiO2-NPs (1 μg/ml). No alterations in cell viability were detected by low LDH leak, and normal cell morphology. Gitrowski et al. 2014 [53]
TiO2-NPs Size: 12 ± 3 nm anatase NPs (95%);
Hydrodynamic diameter (water): 132 ± 0.8 nm.
Caco-2 mono-culture, Caco-2 and HT-29 and Caco-2 and Raji co-cultures. Forty-eight h exposure to TiO2-NPs (0–200 μg/ml). Exposure to TiO2-NPs did not cause overt cytotoxicity.
No apoptosis was observed.
Brun et al. 2014 [15]
Size: ~90 nm for both NPs. Caco-2 Twenty-four h exposure to Ag-, and ZnO-NPs (0–200 μg/ml). Ag- and ZnO-NPs significantly inhibited cell proliferation, with greater effects induced by ZnO-NPs (LD50 for ZnO-NPs: 0.431 μg/ml). Song et al. 2014 [43]
Size: < 100 nm Caco-2 Twenty-four h exposure to Ag-, and Au-NPs (0–1000 μg/ml). A dose-dependent toxic effect of Ag-NPs, with IC50 values of 16.7 and14.9 μg/ml derived from the MTT and trypan blue exclusion assays, respectively.
Au-NPs did not cause any significant decrease in the cell viability.
Aueviriyavit et al. 2014 [47]
Ag-NPs Mean primary size: 7.02 ± 0.68 nm;
Hydrodynamic diameter in acqueous suspension: 14.7 ± 0.2 nm.
Caco-2 Up to 48 h exposure to primary or digested Ag-NPs (0–100 μg/ml). Digested and undigested Ag-NPs decreased the cell viability of Caco-2 cells in a concentration-dependent manner. No differences emerged between NPs. Böhmert et al. 2014 [13]
Ag-NPs Size: 10–100 nm;
Size distribution: less than 10% deviation from the primary size;
Shape and surface chemistry: spherical NPs stabilized with citrate;
Impurities in NP suspensions: none;
Agglomeration status: none in culture medium.
LoVo Up to 48 h exposure to Ag-NPs (0–10 μg/ml). Cell viability (24 h): At 10 μg/ml, the mitochondrial activity significantly decreased to 53% and to 85% compared to controls for cells exposed to 10 and 20 nm Ag-NPs, respectively.
Cell viability (48 h): At 10 μg/ml, 10 nm Ag-NPs mitochondrial activity was reduced to 8% compared to controls. On average, 20–100 nm Ag-NPs resulted in a decrease to 40%.
Miethling-Graff et al. 2014 [105]
Ag-NPs Size: 20 nm;
Hydrodynamic size of Ag-NPs by (A) intensity-weighted distribution
(27.3 nm) and (B) by volume-weighted distribution (21.4 nm);
Average size by TEM: 20.4 nm.
Caco-2 Three h exposure to Ag-NPs (0–20 μg/ml). A significant concentration (10–20 μg/ml) -dependent decrease in cell viability compared with controls. Sahu et al. 2014 [142]
Ag-NPs Size: < 20 nm Caco-2 and Raji B cells in co-culture Twenty-four h exposure to Ag-NPs (0–90 μg/ml) with or without phenolic compounds. Ag-NPs decreased significantly
cellular viability starting from 30 μg/ml with an EC50 of ca. 40 μg/ml.
Kaempferol (10 or 50 mM) had a
protective effect at lower concentrations of Ag-NPs (up to
Resveratrol had no effect.
Martirosyan et al. 2014 [69]
SiO2-NPs Size: 50, 100, 200 nm; Caco-2 Six h exposure to SiO2-NPs incubated in fasting or fed state simulated gastric fluids (0–10 mg/ml). Up to 6 h time point, no cytotoxicity was observed for all sized NPs.
During additional incubation time with fresh medium (24 and 48 h), only 50 nm NPs dispersed in PBS or in fasting simulated fluids, induced a significant cytotoxicity.
Sakai-Kato et al. 2014 [17]
SiO2-NPs Size: 15 and 55 nm;
Size distribution range by TEM: 10.8–29.8 and 41–121 for 15 and 55 nm NPs;
Shape: spherical.
Caco-2 Twenty-four h exposure to SiO2-NPs (0–256 μg/ml). SiO2-NPs (55 nm): a decrease in cell viability (30%) was only observed at the highest tested dose (256 μg/ml).
SiO2-NPs (15 nm): viability was 80% of controls at 32 μg/ml and 20% at 256 μg/ml. IC50: 43 μg/ml.
Tarantini et al. 2015a [44]
TiO2-NPs Size: 12 ± 3 nm (anatase), 22 ± 4 nm (rutile);
Surface area: 82 ± 3 and 73 ± 5 g/m2 for anatase and rutile, respectively
Hydrodynamic diameter (water): 132 ± 1 nm (anatase); >1000 nm (rutile)
Caco-2 Twenty-four h exposure to TiO2-NPs (0–200 μg/ml). Neither anatase, nor rutile NPs induced overt cell toxicity. Dorier et al. 2015 [55]
Size: 22–26 nm ± 10 nm (hydrophilic and hydrophobic TiO2-NPs); 14 ± 7, and 13 ± 6 nm for SiO2-NPs.
Surface areas: 51, 56 (TiO2-NPs); 189.2 and 203.9 (SiO2-NPs) m2/g.
Caco-2 Three and 10 day exposure to TiO2-NPs and SiO2-NPs (100 μg/ml) Three day exposure: TiO2-NPs did not induce significant changes in the CFE of cells compared to controls.
Cytotoxic effects were registered only for 13 ± 6 nm for SiO2-NPs (99% SiO2), with values of cytotoxicity (CFE = 66% ± 4)
Ten day exposure: significant cytotoxic effects were detected after hydrophilic TiO2-NPs (CFE = 72% ± 5) and 13 ± 6 nm SiO2-NP exposure (CFE = 43% ± 4).
Farcal et al. 2015 [56]
Size: 50–70 for ZnO-NPs, and <25 nm for TiO2-NPs;
Size by TEM: 45–170 (ZnO-NPs) 20–60 nm (TiO2-NPs)
Hydrodynamic diameter in in cell culture medium without foetal calf serum: 942 ± 118 (ZnO-NPs); 1080 ± 190 nm (TiO2-NPs).
Purity: 99.7% for anatase TiO2-NPs.
Caco-2 Six and 24 h exposure to ZnO, and TiO2-NPs (0–128 μg/ml) Only ZnO-NPs exert a strong cytotoxic effect on cells as determined by replication indexes. Zijno et al. 2015 [60]
ZnO-NPs TEM size: 20 to 250/50 to 350 nm;
Size in medium: 306 nm;
Surface area: 14 m2/g.
Caco-2 Exposure to ZnO-NPs and ZnO-NPs in co-exposure to palmitic acid or free fatty acids Dose dependent cytotoxic effects were detected for ZnO-NPs (EC50: 25 μg/ml I MTT assay).
Co-exposure of ZnO-NPs and palmitic acid to cells showed the largest cytotoxic effects as indicated by the lowest EC50 value (19 μg/ml), whereas free fatty acids had a higher EC50 value (24 μg/ml).
Cao et al. 2015 [70]
TiO2-NPs Size: 99 ± 30 and 26 ± 12 nm anatase NPs;
Hydrodynamic diameter in water: 233 ± 12 and 497 ± 137 nm for the larger and smaller NPs, respectively.
Hydrodynamic diameter in culture medium: 719 ± 56 and 727 ± 9 nm for the larger and smaller NPs, respectively.
Purity: over 99%.
Caco-2 Twenty-four h exposure to Native NPs and pretreated with digestive fluids (50 and 200 μg/ml) After 24 h exposure, native NPs do not induce any clear loss of viability on cells.
Pretreated NPs are non-toxic to differentiated Caco-2 cells, while can induce a decrease in viability of the undifferentiated Caco-2 cells after 24 h exposure, although the viability remains higher than 86%.
Song et al. 2015 [59]
Size: SW-CNTs ranged between 1.04–1.71 nm; the layer of MW-CNTs is about 8.4 (± 0.9) graphite layers. Caco-2 Up to 72 h exposure to CNTs (0–100 μg/ml). No significant decrease of cell viability was observed at 0.1, 1 and 10 μg/mL doses of four types of CNTs from 4
to 8 h, but the long-lasting treatment (>24 h) increased the cytotoxicity
Chen et al. 2015 [66]
Ag-NPs Size (untreated NPs): mean radius: 3.2 ± 0.1 nm; width: 1.1 ± 0.3 nm;
Size in culture medium (untreated NPs): mean radius: 3.6 ± 0.1 nm; width: 1.2 ± 0.6 nm;
Size (digested NPs): 16.0 ± 0.1 nm and 6.6 ± 1.3 nm (with) and 16.6 ± 0.2 and 7.3 ± 1.7 nm (without cell culture medium).
Caco-2 Twenty-four h exposure to untreated or digested Ag-NPs (0–100 μg/ml). In up to 40 μg/ml Ag no reduction of viability was observed for both NPs.
At concentrations higher than
40 μg/ml digested and undigested particles were almost equally cytotoxic.
Lichtenstein et al. 2015 [38]
Ag-NPs Size: 50 nm;
The average size of Ag-NPs by TEM and DLS was 44.7and 54.9 nm, respectively;
TEM images demonstrated no noticeable aggregation, agglomeration.
Caco- 2 Four h and 24 h exposure to Ag-NPs (0–50 μg/ml). A significant concentration (10–50 μg/ml) -dependent decrease in cell viability compared with controls. Sahu et al. 2016 [143]
Ag-NPs Size: < 20 nm. Caco-2 and Raji B cells in co-culture Three h exposure to Ag-NPs (0–90 μg/ml) with or without a phenolic compound. Ag-NPs induced a dose-dependent decrease in cell viability.
Co-administration with Quercetin protected the cells from the toxic effects of Ag-NPs.
Martirosyan et al. 2016 [68]
Ag-NPs Size: 10–110 nm. T84 Fourty-eight h exposure to Ag-NPs (20 and 100 μg/ml). Little to no change in cell viability compared to controls (acridine orange/ethidium bromide staining).
Significant decrease in cell viability only after 100 μg/ml Ag-NPs doses (ATP-based luminescence assay)
Williams et al. 2016 [35]
Ag-NPs Size: 20 and 200 nm.
Hydrodynamic diameter: 129 and 308 for 20 and 200 nm sized Ag-NPs.
Caco-2/TC7:HT29-MTX co-culture Twenty-four h exposure to Ag-NPs (0–100 μg/ml). Ag-NPs did not induce cytotoxicity at any of the tested concentrations in single cell lines or in co-culture. Georgantzopoulou et al. 2016 [22]
PVP capped Ag-NPs;
Phosphine capped Au-NPs.
Ag-, TiO2-, and Au-NP size: < 20; 7–10 and 15, 80 nm, respectively.
Mean hydrodynamic diameter in DMEM culture medium: 120 ± 4, 896 ± 133 and 51 ± 6, 116 ± 5 nm, respectively.
Caco-2 mono-, and co-culture with THP-1, MUTZ-3 cells in a 3D model of intestinal mucosa Twenty-four h exposure to NPs (0–625 μg/cm2) in both inflamed and not-inflamed conditions Au-NPs and TiO2-NPs did not affect cell viability.
Ag-NPs: the highest concentration induced a significant cytotoxicity in Caco-2 mono-culture > than in co-culture, with no influence due to the inflammatory status.
Susewind et al. 2016 [48]
TiO2-NPs TiO2-NP size; 50 and 100 nm (anatase); 50 nm (rutile); 21 nm (P25Degussa);
Hydrodynamic diameter (DMEM): 227.78 ± 3.62 (anatase 50); 253.40 ± 4.11 (anatase 100); 194.20 ± 2.14 (rutile 50);
193.85 ± 1.86 nm (P25 Degussa).
Caco-2 cells Twenty-four, and 72 h exposure to NPs (0–50 μg/ml) No change in Caco-2 cell viability was evident at 24 h-exposure.
72 h exposure: 50 nm anatase (10, 25, 50 μg/ml), 100 nm anatase (50 μg/ml), 50 nm rutile (50 μg/ml), and P25 Degussa TiO2-NPs (25, 50 μg/ml) reduced cell viability.
Tada-Oikawa et al. 2016 [52]
TiO2-NPs Size: < 25 nm anatase NPs (99%);
Surface area: 45–55 m2/g;
Hydrodynamic diameter (water): 604 ± 24 nm.
HT-29 Up to 48 h exposure to TiO2-NPs (0–36 μg/ml). No significant cytotoxic effect of TiO2-NPs was observed in LDH and MTT assays at all concentrations
after 6, 24, and 48 h exposure.
Ammendolia et al. 2017 [50]
  1. Caco-2 cells human colorectal adenocarcinoma cells, CFE colony forming efficiency, COOH- SW-CNTs carboxylic acid functionalized single walled carbon nanotubes, CTAB cetyltrimethylammonium bromide, DLS dynamic light scattering, DS digestion simulated, EC 50 half maximal effective concentration, HT-29 human colon carcinoma cells, HT29-MTX human adenocarcinoma mucus secreting cells, IC inhibition concentration, LD50 Lethal dose, LoVo human colon carcinoma cell line, MUTZ-3 human dendritic cells, MW-CNTs multi-walled carbon nanotubes, PAA polyacrylic acid, PAH polyelectrolyte poly(allylamine) hydrochloride, PEG poly-ethylene glycol, PEG-SW-CNTs poly(ethylene glycol) functionalized single walled carbon nanotubes, Raji B line human Burkitt’s lymphoma cells, RKO human colon adenocarcinoma cells, SW- CNTs single walled- carbon nanotubes, SW480 human colon adenocarcinoma cells, T84 human colonic epithelial cells, TEM transmission electron microscopy, THP-1 Human macrophages