Titanium dioxide

Basic toxicokinetics

Administrative data

Endpoint:

basic toxicokinetics in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

other: not rateable

Data source

Reference

Reference Type:

publication

Title:

Titanium Dioxide, NM-100, NM-101, NM-102, NM-103, NM-104, NM-105: Characterisation and Physico-Chemical Properties - JRC Repository: NM-Series of Representative Manufactured Nanomaterials

Author:

Rasmussen et. al.

Year:

2014

Bibliographic source:

European Commission - Joint Research Centre, science and policy reports, JRC 86291, ISBN 978-92-79-38188-1 (pdf), p.128 -140

Materials and methods

Objective of study:

bioaccessibility (or bioavailability)

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Series on Testing and Assessment No. 29 (23-Jul-2001): Guidance document on transformation/dissolution of metals and metal compounds in aqueous media

Version / remarks:

test medium, loading and test duration adopted for toxicokinetics assessment

Principles of method if other than guideline:

An internationally agreed guideline does not exist for this test (e.g. OECD). However, similar tests have been conducted with several metal compounds in previous risk assessments (completed under Regulation (EEC) No 793/93) and in recent preparation for Regulation (EC) No 1907/2006.

The test was performed on the basis of OECD Series on Testing and Assessment No. 29 (2001; ENV/JM/ MONO(2001)9), the Standard Operating Procedure for Bioelution Testing of Metals, Inorganic Metal Compounds, and Complex Metal-Containing Materials: Simulated Gastric Fluid (version 09.11.2018 submitted to ECVAM for acceptance) with some modifications that are described in details in this robust study summary. The test media were artificial physiological media: artificial lysosomal fluid (ALF). Gamble's solution (GMB) and Hatch`s solution (HTC).

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Titanium dioxide

EC Number:

236-675-5

EC Name:

Titanium dioxide

Cas Number:

13463-67-7

Molecular formula:

O2Ti

IUPAC Name:

dioxotitanium

Test material form:

solid: particulate/powder

Details on test material:

Purity: 98.5 % (NM-100); 99 % (NM-101); 95 % (NM-102); 89 % (NM-103); 90 % (NM-104)
Particle size: 200-220 nm (NM-100); < 10 nm (NM-101); 20 nm (NM-103); 20 nm (NM-104); 21 nm (NM-105)
Phase: anatase (NM-100); anatase (NM-101); anatase (NM-102); rutile (NM-103); rutile (NM-104); rutile/anatase (NM-105)
Specific surface area (BET) (m²/g): > 250 (NM-101); 90 (NM-102); 60 (NM-103); 60 (NM-104); 50 ± 15 (NM-105)

Specific details on test material used for the study:

INFORMATION ON NANOMATERIALS
- Chemical Composition: TiO2

NM-100:
- Impurities (ppm): 900 (Al); 2800 (Si); 2100 (P); 2500 (K); 300 (Cr); 4900 (Fe)

NM-101:
- Impurities (ppm): 900 (Al); 2900 (Si); 2200 (S); 2700 (P)

NM-102:
- Impurities (ppm): 500 (Al); 800 (Si); 700 (Fe)
- Z-Average (nm): 408.9 ± 23.2
- Polydispersity index (PdI): 0.427 ± 0.012

NM-103:
- Impurity (ppm): 34300 (Al); 6800 (Si); 2600 (S); 600 (Fe)
- Z-Average (nm): 119.6 ± 11.0
- Weight of coating (wt %): 2
- PdI: 0.244 ± 0.33

NM-104:
- Impurity (ppm): 32 200 (Al); 1800 (Si); 3200 (S)
- Z-Average (nm): 127.3 ± 2.2
- Weight of coating: 2
- PdI: 0.217 ± 0.010

NM-105:
- Impurity (ppm): 400 (al); 700 (Si)
- Z-Average (nm): 130.4 ± 4.5
- PdI: 0.141 ± 0.006

Test animals

Details on test animals or test system and environmental conditions:

Test principle in brief:
- single loading of test substance 0.32 mg/L,
- Caco2 medium: samples taken after 24 hours agitation
- the media was determined on duplicate samples
- measurement (ICP-OES) dissolved titanium concentrations after

The aim of this test was to assess the dissolution of titanium dioxides NM-100 -105 in 3 different media: Caco2, Gambles solution and bovine serum albumin (BSA) dispersion.

Administration / exposure

Details on exposure:

Titanium dioxides NM-102 to NM-105 concentrations in Caco2 medium was assessed after

Doses / concentrations

Dose / conc.:

0.32 other: mg test item / L Caco2 cell medium

Details on study design:

Test setup
At least 15.36 mg of TiO2 NM was prewetted with 30 µL EtOH (0.5 vol%). Then 970 μl 0.05% BSA water were added by pipette while slowly rotating. The remaining 5 ml 0.05% BSA water was added and the vial was placed on ice for at least 5 minutes. It was sonicated in an ice-water bathfor 16 min at 400 W and 10% amplitude, 3,136 MJ/m³.
The media was determined for dissolved titanium concentrations on duplicate samples. All solutions were sampled after 24 h to measure total dissolved titanium concentrations (ICP-OES) after centrifugation (60 min, 20000x g) and 0.2 μm filtration (Syringe Filter w / 0.2 μm, CAMECA). In addition, pH were recorded.
The elemental background concentrations in the Caco2 cell meda were determined by ICP-MS (by Eurofins, DK-6600 Vejen, Denmark) on three doublet samples. The elemental concentrations of titanium after dissolution were determined in two sub-samples for each nanomaterial.

Reagents*:
Nanopour water
EtOH - 96 vol%
Bovine serum - sterile, Sigma (catalogue number: A-9418)

*NANOGENOTOX dispersion protocol: Jensen, K.A., Kembouche, Y., Christiansen, E., Jacobsen, N.R., Wallin, H. WP 4: Physicochemical Characterisation of Manufactured Nanomaterials (MNs) and Exposure Media (EMs). Final protocol for producing suitable manufactured nanomaterial exposure media, July 2011, p. 1-33.

Instrumental and analytical set-up for ICP-OES instrument:
Varian 720-ES, CODA-CERVA, Agilent Technologies

Details on dosing and sampling:

Loading:
0.32 mg TiO2 (NM-100 to NM-105) / L Coca2 cell medium

Results and discussion

Main ADME results

Main ADME results 1

Type:

other: Bioaccessibility Caco2 cell medium, 24 h at 37°C (0.32 mg/mL (TiO2 NM-100) loading, centrifugation (60 min, 20000x g) and filtration (0.2 μm) for phase separation)

Results:

796 μg total Ti/L (dissolved)

Main ADME results 2

Type:

other: Bioaccessibility Caco2 cell medium, 24 h at 37°C (0.32 mg/mL (TiO2 NM-101) loading, centrifugation (60 min, 20000x g) and filtration (0.2 μm) for phase separation)

Results:

3414 μg Ti/L (dissolved)

Main ADME results 3

Type:

other: Bioaccessibility Caco2 cell medium, 24 h at 37°C (0.32 mg/mL (TiO2 NM-102) loading, centrifugation (60 min, 20000x g) and filtration (0.2 μm) for phase separation)

Results:

1741 μg Ti/L (dissolved)

Main ADME results 4

Type:

other: Bioaccessibility Caco2 cell medium, 24 h at 37°C (0.32 mg/mL (TiO2 NM-103) loading, centrifugation (60 min, 20000x g) and filtration (0.2 μm) for phase separation)

Results:

222 μg Ti/L (dissolved)

Main ADME results 5

Type:

other: Bioaccessibility Caco2 cell medium, 24 h at 37°C (0.32 mg/mL (TiO2 NM-104) loading, centrifugation (60 min, 20000x g) and filtration (0.2 μm) for phase separation)

Results:

3386 μg Ti/L (dissolved)

Main ADME results 6

Type:

other: Bioaccessibility Caco2 cell medium, 24 h at 37°C (0.32 mg/mL (TiO2 NM-105) loading, centrifugation (60 min, 20000x g) and 0.2 μm for phase separation)

Results:

2724 μg Ti/L (dissolved)

Bioaccessibility (or Bioavailability)

Bioaccessibility (or Bioavailability) testing results:

The bioaccessability of titanium dioxide was determined in vitro by simulating dissolution in Caco2 cell medium, with a loading of 0.32 mg/mL (TiO2 NM-100 to 105).

After 24 h in Caco2 medium (Caco2, pH 7.5 - 8.0, loading 0.32 mg/L nano-TiO2) dissolved titanium concentrations (operationally defined as the dissolved titanium fraction after filtration (0.2 μm) and centrifugation (20000x g) were 796 μg/L (NM-100); 3414 μg/L (NM-101); 1741 μg/L (NM-102); 222 μg/L (NM-103); 3386 μg/L (NM-104) and 2724 μg/L (NM-105).

NM-100 is soluble in Caco2 after 24 h in vitro incubation test and the TiO2 NM-101 to NM-105 are slightly soluble in Caco2 medium. Mean total titanium concentrations were highest in the Caco2 cell medium for titanium dioxide NM-104: 3900 μg/L of total titanium was found in the dissolved phase after 24 h.

Any other information on results incl. tables

Results of titanium dissolution in Caco2 cell medium

Table 2 lists the dissolved Titanium concentration in the incubation Caco2 medium corrected for the background concentrations in the incubation Caco2 medium.

Table 2: Background-corrected* elemental concentration in the test medium after 24-hour dissolution tests with TiO2 NM (n=2).

MdL	Element	unit	NM-100 (σ)	NM-101 (σ)	NM-102 (σ)	NM-103 (σ)	NM-104 (σ)	NM-105 (σ)
5	Ti	µg/L	796 (2)	3414 (1683)	1741 (683)	222 (337)	3386 (3900)	2724 (3846)

MDL: Minimum detection limit in the raw analysis; - denotes not detected; < denotes background corrected concentration lower than 0.1 x MDL. Measurements were performed twice, i.e. n=2 * the background correction combined with a small number of repeated measurements mean that the  value may be larger than the corrected measurement value

Test temperature:       37°C

Method validation summary (ICP-OES)

Minimum detection limit (MDL): < 5 μg Ti/L

Applicant's summary and conclusion

Conclusions:

In the Coca2 cell medium, titanium dioxide was poorly soluble. NM-100 is soluble in Caco2 after 24 h in vitro incubation test and the TiO2 NM-101 to NM-105 are slightly soluble in Caco2 medium.

A maximum of 796 μg/L total dissolved titanium was measured in Caco2 medium after 24 h.
A maximum of 796 μg/L total dissolved titanium was measured in Caco2 medium after 24 h for the NM-100.
A maximum of 3414 μg/L total dissolved titanium was measured in Caco2 medium after 24 h for the NM-101.
A maximum of 1741 μg/L total dissolved titanium was measured in Caco2 medium after 24 h for the NM-102.
A maximum of 222 μg/L total dissolved titanium was measured in Caco2 medium after 24 h for the NM-103.
A maximum of 3386 μg/L total dissolved titanium was measured in Caco2 medium after 24 h for the NM-104.
A maximum of 2724 μg/L total dissolved titanium was measured in Caco2 medium after 24 h for the NM-105.

Executive summary:

The objective of this study was to investigate the solubility of different titanium dioxide nanomaterials (NM-100 - NM-105) in intestine system (Caco2 cell medium).