Magnesium diniobate

Skin irritation / corrosion

Administrative data

Endpoint:

skin irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2017-07-13 to 2017-08-18

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2017

Report date:

2018

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

2015-07-28

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method B.46 (In Vitro Skin Irritation: Reconstructed Human Epidermis Model Test)

Version / remarks:

2009-07-23

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

signed 2015-09-14

Test material

Test material information

Constituent 1

Reference substance name:

Magnesium diniobate

EC Number:

235-310-7

EC Name:

Magnesium diniobate

Cas Number:

12163-26-7

Molecular formula:

Mg.2NbO3

IUPAC Name:

Magnesium diniobate

Test material form:

solid: particulate/powder

Details on test material:

Test Item: Magnesium diniobate
Molecular formula: MgNb2O6
Molecular weight: 306.11 g/mol
Appearance: White powder
Storage conditions: Ambient temperature, keep container tightly closed, dry

Specific details on test material used for the study:

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: At room temperature

In vitro test system

Test system:

human skin model

Source species:

human

Cell type:

other: normal, human-derived epidermal keratinocytes

Cell source:

other: humans

Source strain:

other: not applicable

Details on animal used as source of test system:

not applicable

Justification for test system used:

In an international prevalidation study performed by ECVAM, the in vitro skin irritation test using the human skin model EpiDerm™ and measurement of cell viability by dehydrogenase conversion of MTT into a blue formazan salt have turned out as a sufficiently promising predictor for skin irritancy potential.

Vehicle:

other: Dulbecco's phosphate buffered saline (DPBS)

Details on test system:

RECONSTRUCTED HUMAN EPIDERMIS (RHE) TISSUE
- Model used: EpiDerm™ skin model (source: MatTek Corporation, 82105 Bratislava, Slovakia)
- Tissue lot number: 25837
- Delivery date: 2017-08-15

TEMPERATURE USED FOR TEST SYSTEM
- Temperature of pre-incubation: 37 ± 1.5 °C (23.5 hours)
- Temperature used during treatment / exposure: 37 ± 1.5 °C for 35 minutes, room temperature for 25 minutes
- Temperature of post-treatment incubation: 37 ± 1.5 °C (41 hours)

REMOVAL OF TEST MATERIAL AND CONTROLS
After the end of the treatment interval the inserts were removed and the tissues were rinsed with DPBS for at least 15 times in order to remove any residual test material. After the rinsing the inserts were submerged in 150 mL DPBS at least three times. Afterwards the inserts were once again rinsed with DPBS.
The tissues were then transferred into plates with assay medium. Tissues were incubated for nearly 23 hours at 37 ± 1.5 °C, 5 ± 0.5 % CO2. After incubation, the medium was changed (pre-warmed fresh medium). Thereafter tissues were incubated for another 18 hours at 37 ± 1.5 °C, 5 ± 0.5 % CO2. The complete incubation time was approx. 41 hours.

MTT DYE USED TO MEASURE TISSUE VIABILITY AFTER TREATMENT / EXPOSURE
- MTT concentration: 1 mg/mL (300 µL/ well)
- Incubation time with MTT: 3 hours
- Extraction of Formazan: after the incubation period, the tissues were transferred to the MTT-plates, prefilled with 300 µL of MTT and incubated for 3 hours. After MTT incubation the tissues were rinsed three times with DPBS, and carefully dried with blotting paper. The tissues were transferred into new plates containing extractant solution (isopropanol) in each well so that the tissues were covered completely and the plate was sealed to inhibit the evaporation of isopropanol. The formazan salt was extracted for 3 hours while shaking at room temperature.
After the extraction was completed, the inserts were pierced with an injection needle to allow the extract to run into the well from which the insert was taken and the insert was discarded. The 24-well plates were placed on a shaker for 15 minutes until the solution was homogeneous in colour.
Per each tissue, 3 × 200 μL aliquots of the blue formazan solution were transferred into a 96-well flat bottom microtiter plate. The optical density was read in a microplate reader. Mean values were calculated from the 3 wells per tissue.
- Spectrophotometer: Versamax® Molecular Devices
- Wavelength: 570 nm

TEST FOR COLOUR INTERFERENCE
Before the test started, a functional check for colour interference was performed. 25 ± 2 mg of the test item were added to deionised water. The mixture was incubated in the incubator (37 ± 1.5 °C, 5 ± 0.5 % CO2) for 60 minutes. At the end of the exposure time, the mixture was shaken and the presence and intensity of the staining (if any) was evaluated.

TEST FOR DIRECT MTT REDUCTION
The test item was evaluated for its potential to interfere with MTT assay. To test if a test item directly reduces MTT, 25 ± 2 mg of the test item were added to 1 mL of the MTT-solution (1mg/mL) and was incubated in the incubator (37 ± 1.5 °C, 5 ± 0.5% CO2) for 60 minutes. Untreated MTT medium was used as control.

FUNCTIONAL MODEL CONDITIONS WITH REFERENCE TO HISTORICAL DATA
- Viability: tissues pass analysis for tissue viability
- Barrier function: tissues pass analysis for tissue functionality
- Morphology: presence of a functional stratum corneum, a viable basal cell layer, and intermediate spinous and granular layers
- Contamination: absence of bacteria, yeast, and other fungi (long term antibiotic, antimycotic free culture) as well as absence of HIV1- virus, Hepatitis B virus, and Hepatitis C virus
Please also refer to the field "Attached background material" below.

PREDICTION MODEL / DECISION CRITERIA
The mean optical density (OD) of the three negative control tissues was calculated after blank correction. This value corresponds to 100% tissue viability in the current test. For each individual tissue treated with the test item or the positive control the individual relative tissue viability is calculated according to the following formula:
relative viability (%) = (mean OD test item or positive control/ mean OD of negative control) x 100
For the test item and the positive control, the mean relative viability ± relative standard deviation of the three individual tissues was calculated and used for classification according to the following prediction model: if the mean relative tissue viability of three individual tissues is less or equal to 50 % of the negative control, the test item needs to be classified and labelled for its skin irritation potential: Category 2 – irritant, H315 according to Regulation (EC) No 1272/2008.

Control samples:

yes, concurrent negative control

yes, concurrent positive control

Amount/concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): approx. 25 mg (~ 39 mg/cm²) of the test item, wetted with vehicle

VEHICLE
- Amount(s) applied (volume or weight with unit): 25 µL DPBS

NEGATIVE CONTROL
- Amount(s) applied (volume or weight): 30 µL DPBS

POSITIVE CONTROL
- Amount(s) applied (volume or weight): 30 µL of a 5% SLS in deionised water

Duration of treatment / exposure:

60 minutes

Duration of post-treatment incubation (if applicable):

41 hours

Number of replicates:

triplicates

Results and discussion

In vitro

Results

Irritation / corrosion parameter:

% tissue viability

Value:

101.2

Vehicle controls validity:

not examined

Negative controls validity:

valid

Positive controls validity:

valid

Other effects / acceptance of results:

- OTHER EFFECTS:
- Visible damage on test system: no
- Direct-MTT reduction: Since the MTT solution did not turn blue/purple, the test item was not considered to reduce MTT and an additional test with freeze-killed tissues did not have to be performed in the main experiment.
- Colour interference with MTT: Since the test item did not dye water and did not change colour in the presence of water, an additional test with viable tissues (but without MTT addition) was not necessary.

ACCEPTANCE OF RESULTS:
- Acceptance criteria met for negative control: after treatment with the negative control, the absorbance values (mean: 1.337) were well within the required acceptability criterion of mean OD ≥ 0.8 and ≤ 2.8 for the 60 minutes treatment interval.
- Acceptance criteria met for positive control: treatment with the positive control induced a decrease of the relative absorbance to 4.4 % compared with the negative control (acceptability criterion: positive control is ≤ 20 %).
- Acceptance criteria met for variability between replicate measurements: the standard deviations between the % variability values of the test item, the positive and negative controls in the main test were 2.0, 0.3 and 11.5, respectively (threshold of the "OECD Guideline for the Testing of Chemicals 439: In vitro Skin Irritation: Reconstructed Human Epidermis Test Method”: < 18%).
Please refer to the field "Any other information on results incl. tables" below

Any other information on results incl. tables

HISTORICAL DATA

Positive Control		Negative Control [OD570]
Mean Viability	4.37%	Mean Absorption	1.74
Rel. Standard Deviation	21.60%	Rel. Standard Deviation	9.40%
Range of Viabilities	2.20 % - 6.78 %	Range of Absorbance	1.34– 2.00
Mean Absorption	0.08
Rel. Standard Deviation	20.12%
Range of Absorbance	0.03 - 0.11

Data of 103studies performed from July 2015 untilMarch2017.

RESULTS AFTER TREATMENT WITH MAGNESIUM DINIOBATE AND THE CONTROLS

Dose Group	Tissue No.	Absor-bance 570 nm Well 1	Absor-bance 570 nm Well 2	Absor-bance 570 nm Well 3	Mean Absor-bance of 3 Wells	Mean Absor-bance of three wells blank corrected	Mean Absor-bance of 3 tissues after blank correction	Rel. viability [%] Tissue 1, 2 ,3*	Standard Deviation	Mean Rel. Viability [%]**
Blank		0.038	0.038	0.038	0.038
Negative Control	1	1.349	1.359	1.357	1.355	1.317	1.337	98.6	2.0	100.0
	2	1.415	1.405	1.396	1.405	1.368		102.3
	3	1.374	1.356	1.358	1.363	1.325		99.1
Positive Control	1	0.087	0.092	0.094	0.091	0.053	0.058	4.0	0.3	4.4
	2	0.098	0.098	0.098	0.098	0.060		4.5
	3	0.100	0.099	0.099	0.100	0.062		4.6
Test Item	1	1.233	1.223	1.244	1.233	1.196	1.353	89.5	11.5	101.2
	2	1.396	1.397	1.400	1.398	1.360		101.7
	3	1.534	1.549	1.538	1.540	1.502		112.4

* Relative viability [rounded values]:100 x (absorbance (test item/ positive control/negative control))/ (mean absorbance (negative control))

** Mean relative viability [rounded values]:100 x (mean absorbance (test item/ positive control/negative control))/ (mean absorbance (negative control))

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met

Conclusions:

According to the Regulation (EC) No 1272/2008 and subsequent regulations, magnesium diniobate is not irritating to the skin.