Niobium doped titanium dioxide

Skin irritation / corrosion

Administrative data

Endpoint:

skin irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

October 10, 2018 - October 12, 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

Report date:

2018

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 439 (In Vitro Skin Irritation: Reconstructed Human Epidermis Test Method)

Version / remarks:

2015

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Niobium doped titanium dioxide

EC Number:

951-670-4

Molecular formula:

Nb:TiO2

IUPAC Name:

Niobium doped titanium dioxide

Test material form:

solid

In vitro test system

Test system:

artificial membrane barrier model

Source species:

human

Cell type:

non-transformed keratinocytes

Vehicle:

unchanged (no vehicle)

Details on test system:

RECONSTRUCTED HUMAN EPIDERMIS (RHE) TISSUE
- Model used: SkinEthic RHE-model RHE/S/17 from Episkin/SkinEthic Laboratories, Lyon, France
- Tissue batch number(s): 18-RHE-118

TEMPERATURE USED FOR TEST SYSTEM
- Temperature used during treatment / exposure: room temperature
- Temperature of post-treatment incubation: 37°C

REMOVAL OF TEST MATERIAL AND CONTROLS
- Volume and number of washing steps: once gently rinsed with a min. of 25 µL DPBS
- Observable damage in the tissue due to washing: no

MTT DYE USED TO MEASURE TISSUE VIABILITY AFTER TREATMENT / EXPOSURE
- MTT concentration: 1 mg/mL
- Incubation time: 3 hours at 37°C and 5% CO2
- Wavelength: 570 nm

FUNCTIONAL MODEL CONDITIONS
see table 1

NUMBER OF REPLICATE TISSUES: 3

NUMBER OF INDEPENDENT TEST SEQUENCES / EXPERIMENTS TO DERIVE FINAL PREDICTION:

PREDICTION MODEL / DECISION CRITERIA
A test item is identified as requiring classification and labelling according to UN GHS (Category 2 or Category 1) if the mean percent tissue viability after exposure and post-treatment incubation is ≤ 50%. Since the in vitro skin irritation test according to OECD 439 cannot resolve between UN GHS Categories 1 and 2, further information on skin corrosion is required to decide on its final classification.

Acceptability of the Quality Control Data of the Skin Model with Reference to Historical Batch Data:
The OD values for the negative control shall be in the range of ≥ 0.8 and ≤ 3.0 as given in OECD Guideline 439.
Acceptability of the Positive and Negative Control stated by Episkin/SkinEthic Laboratories:
The negative control data meet the acceptance criteria if the mean OD value of the 3 tissues is ≥ 1.2 at 570 nm. The standard deviation value is considered valid if ≤ 18% of group mean-value.
The positive control data meet the acceptance criteria if the mean viability value, expressed as % of the negative control, is < 40%. The standard deviation value is considered valid if ≤ 18% of group mean-value.

Control samples:

yes, concurrent negative control

yes, concurrent positive control

Amount/concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 16 ± 2 mg per tissue

NEGATIVE CONTROL
- Amount applied (volume or weight): 16 ± 0.5 µL per tissue

POSITIVE CONTROL
- Amount applied (volume or weight): 16 ± 0.5 µL per tissue

Duration of treatment / exposure:

42 min

Duration of post-treatment incubation (if applicable):

42 hours

Number of replicates:

3

Results and discussion

In vitro

Results

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

1st

Value:

85.5

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Remarks:

100%

Positive controls validity:

valid

Remarks:

1%

Remarks on result:

no indication of irritation

Other effects / acceptance of results:

- OTHER EFFECTS:
- Visible damage on test system: no
- Direct-MTT reduction: no
The pre-test for direct MTT-reducing capacity of the test item did not result in blue colour, i.e. the test item is not a direct MTT reducer.
- Colour interference with MTT: no
In the pre-test, medium colouration by the test item was observed, but no tissues were stained during the study. Therefore, no additional tissues for colour control were treated according to the SOP Skinethic Skin Irritation Test (2009).

ACCEPTANCE OF RESULTS:
- Acceptance criteria met for negative control: yes
- Acceptance criteria met for positive control: yes
- Acceptance criteria met for variability between replicate measurements: yes

Any other information on results incl. tables

Table 3: Results

Group	Tissue 1		Tissue 2		Tissue 3		Mean		SD
	OD	viability	OD	viability	OD	viability	OD	viability	viability
Negative Control	2.071	106.7%	1.787	92.1%	1.965	101.2%	1.941	100.00	7.4%
Positive Control	0.020	1.0%	0.019	1.0%	0.020	1.0%	0.020	1.0%	0.0%
Test item	1.595	82.2%	1.651	85.1%	1.729	89.1%	1.658	85.5%	4.1%

Table 4: Acceptability of the Test

Acceptability of the Quality Control Data of the Skin Model with Reference to Historical Batch Data:

	Acceptance Criterion	Result
Negative control OD	≥ 0.8 and ≤3.0	1.787 to 2.071

Acceptability of the Positive and Negative Control stated by Episkin/SkinEthic Laboratories:

	Acceptance Criterion	Result
Mean OD negative control	≥ 1.2	1.941
Mean viability positive control	<40%	1.0%
SD of group-mean value	≤ 18%	0.0% (positive control) 7.4% (negative control)

 

Acceptability of the Positive and Negative Control based on Historical Data of the Testing Laboratory:

	Acceptance Criterion	Result
Mean OD negative control	≥ 1.420	1.941
Mean viability positive control	≤ 2.82%	1.0%

Test Item Data Acceptance Criteria:

	Acceptance Criterion	Result
SD of group-mean value	≤ 18%	4.1%

The study met all acceptance criteria.

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met

Conclusions:

Under the conditions of the present study, the test item is not considered to possess an irritant potential to skin.

Executive summary:

A study according OECD TG 439 was conducted to investigate the potential of the test item to induce skin irritation in an in vitro human skin model. The test item was applied topically to a human reconstructed skin model followed by determination of the cell viability. Cell viability was determined by enzymatic conversion of vital dye MTT into a blue formazan salt and measurement of the formazan salt after extraction from tissues. The percent reduction of cell viability in comparison to untreated negative controls was used to predict the skin irritation potential.

Triplicates of the human skin RHE-model were treated with the test item, the negative or the positive control for 42 minutes (± 1 minute)16 µL of either the negative control (DPBS-buffer) or the positive control (5% aqueous solution of sodium dodecyl sulfate) were applied to the tissues. Before application of 16 mg of the solid test item, 10 µL of deionized water was spread to the epidermis surface to improve the contact between the test item and the epidermis.

All acceptability criteria after treatment with the negative control (DPBS-buffer) and the positive control (5% aqueous solution of sodium dodecyl sulfate) were met.

Following treatment with the test item, the tissue viability was 85.5% and thus, higher than 50%, i.e. according to OECD 439 the test item is considered as non-irritant to skin (UN GHS: No Category).