Sodium bis(trifluoromethylsulfonyl)imide

Skin irritation / corrosion

Administrative data

Endpoint:

skin corrosion: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

July 2021

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2021

Report date:

2021

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 431 (In Vitro Skin Corrosion: Reconstructed Human Epidermis (RHE) Test Method)

Deviations:

no

Principles of method if other than guideline:

The corrosivity potential of a chemical may be predicted by measurement of its cytotoxic effect, as reflected in the MTT [3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, Thiazolyl blue; CAS number 298-93-1] assay, on EPISKINTM(SM) reconstituted human epidermis. This method is approved by international regulatory agencies as a replacement for the identification of corrosives in the in vivo Rabbit skin assay (OECD 404) and is specifically approved as a replacement for the in vivo skin corrosivity test within OECD 431.
The present test is based on the experience that corrosive chemicals/formulations/products/mixtures show cytotoxic effects following short-term exposure of the stratum corneum of the epidermis. The purpose of this study is to predict the skin corrosivity potential of a chemical by assessment of its effect on a reconstituted human epidermis.
EPISKINTM(SM) is a three-dimensional human skin model comprising a reconstructed epidermis with a functional stratum corneum. Its use for skin corrosivity testing involves the topical application of test materials to the surface of the skin, and the subsequent assessment of their effects on cell viability. Cytotoxicity is expressed as the reduction of mitochondrial dehydrogenase activity measured by formazan production from MTT (Fentem et al., 1998). The test can be used for classification as not corrosive, or as 1A, 1B or 1C (COMMISSION REGULATION (EU) 2016/863 of 2016).

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

sodium trifluoro[(trifluoromethanesulfonylazanidyl)sulfonyl]methane

EC Number:

804-361-2

Cas Number:

91742-21-1

Molecular formula:

C2F6NO4S2.Na

IUPAC Name:

sodium trifluoro[(trifluoromethanesulfonylazanidyl)sulfonyl]methane

Test material form:

solid: particulate/powder

Specific details on test material used for the study:

Purity: 99%

In vitro test system

Test system:

human skin model

Remarks:

EPISKINTM(SM) is a three-dimensional human skin model comprising a reconstructed epidermis with a functional stratum corneum

Source species:

human

Details on animal used as source of test system:

EPISKINTM (SM) (Manufacturer: SkinEthic, France, Batch No.: 21-EKIN-022, Expiry Date: 07 June 2021) is a three-dimensional human epidermis model. Adult human-derived epidermal keratinocytes are seeded on a dermal substitute consisting of a collagen type I matrix coated with type IV collagen. A highly differentiated and stratified epidermis model is obtained after 13-day culture period comprising the main basal, supra basal, spinous and granular layers and a functional stratum corneum (Tinois et al., 1994). Its use for skin corrosivity testing involves topical application of test materials to the surface of the epidermis, and the subsequent assessment of their effects on cell viability.

Justification for test system used:

The EPISKINTM(SM) model has been validated for in vitro corrosivity testing in an international validation study and its use is recommended by the relevant OECD guidelines for corrosivity testing (OECD No. 431); therefore, it was considered to be suitable for this study.

Details on test system:

RECONSTRUCTED HUMAN EPIDERMIS (RHE) TISSUE
- Model used: EPISKINTM(SM)
- Tissue batch number(s): 21-EKIN-022,
- Expiring date: 07 June 2021
- Date of initiation of testing: 3 June 2021

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

REMOVAL OF TEST MATERIAL AND CONTROLS
After 4 hours incubation time, the EPISKINTM (SM) units were removed and rinsed thoroughly with PBS to remove any remaining material from the epidermal surface as much as possible. The rest of the PBS was removed from the epidermal surface with a pipette (without touching the epidermis).

MTT DYE USED TO MEASURE TISSUE VIABILITY AFTER TREATMENT / EXPOSURE
- MTT concentration: 2 mL of 0.3 mg/mL MTT working solution
- Incubation time: 3 hours and 5 minutes
- Wavelength: The OD (optical density or absorbance) of the samples was measured using a plate reader at 570 nm

PREDICTION MODEL / DECISION CRITERIA (choose relevant statement)
- The test substance is considered to be corrosive to skin if, for 2 disks, both disks have mean viability of < 35% = Corrosive (at the corresponding incubation period). For more than 2 disks, If the mean value is < 35% and the variability is less than 50% = Corrosive
- The test substance is considered to be non-corrosive to skin if, for 2 disks, both disks have mean viability of ≥ 35% = Non-Corrosive. For more than 2 disks, If the mean value is ≥ 35% and the variability is less than 50% = Non-Corrosive
- Justification for the selection of the cut-off point(s) if different than recommended in TG 431 and 439: The cut-off value of 35% and classification method was validated in an international validation study of this kit (Fentem, 1998).

Control samples:

yes, concurrent negative control

yes, concurrent positive control

Amount/concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 20mg

VEHICLE
- Amount(s) applied (volume or weight with unit) :100 μL physiological saline- Concentration (if solution):

NEGATIVE CONTROL
- Concentration (if solution): 50 μL

POSITIVE CONTROL
- Concentration (if solution): 50 μL

Duration of treatment / exposure:

4 hours (+ 7 minute)

Results and discussion

In vitro

Results

Irritation / corrosion parameter:

% tissue viability

Value:

> 35

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

other: mean cell viability was 132.8% compared to the negative control, which is above the threshold of 35%

Any other information on results incl. tables

VALIDITY OF THE TEST

	Validity criteria (OECD No. 431.)
	Blank	Negative control	Positive control	Test Item
The mean OD	< 0.1	≥ 0.6 and ≤ 1.5	-	-
The Difference of viability %	-	≤ 30	≤ 30*	≤ 30*
The mean viability %	-	-	≤ 20	-

*Note: This measure of variability between individual results applies between 20-100% viability and ODs ≥ 0.3.

INTERPRETATION OF TEST RESULTS

The prediction model below corresponds to the methods agreed by EU regulatory agencies in line with OECD No. 431 (OECD, 2019).

The cut-off value of 35% and classification method was validated in an international validation study of this kit (Fentem, 1998).

For 2 disks:

If both disks have mean viability of ≥ 35% = Non-Corrosive
If both disks have mean viability of < 35% = Corrosive (at the corresponding incubation period)

For more than 2 disks:

If the mean value is ≥ 35% and the variability is less than 50% = Non-Corrosive If the mean value is < 35% and the variability is less than 50% = Corrosive

Otherwise:

If the classification is not made with these criteria, retest with 2 more disks. Take the mean of the 4 disks to classify as above or below 35%. Outlier values may be excluded where there are scientific reasons, such as where application or rinsing is difficult and that the Study Director considers that a result is not representative.

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met

Conclusions:

Results from an In vitro EPISKINTM (SM) model test with Sodium bis(trifluoromethane)sulfonimide indicate that the test item is not corrosive to the skin.

Executive summary:

An in vitro skin corrosivity test of the test item Sodium bis(trifluoromethane)sulfonimide was performed in a reconstructed human epidermis model. The model, EPISKINTM(SM) is designed to predict and classify the corrosive potential of chemicals by measuring its cytotoxic effect as reflected in the MTT (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay (detailed in 9.7. section). The corrosivity of the test item was evaluated according to the OECD No. 431 guideline.

Disks of EPISKINTM(SM) were treated with Sodium bis(trifluoromethane)sulfonimide and incubated for 4 hours at room temperature. Exposure of test material was terminated by rinsing with Phosphate Buffered Saline solution. The viability of each disk was assessed by incubating the tissues for 3 hours with MTT solution, to evaluate cytotoxicity. The precipitated formazan crystals were then extracted using acidified isopropanol and quantified spectrophotometrically.

Physiological saline (0.9% (w/v) NaCl solution) and glacial acetic acid treated epidermis were used as negative and positive controls, respectively (two units / control). Two additional disks were used to provide an estimate of colour contribution (NSCliving%) from the test item. For each treated tissue viability was expressed as a % relative to the negative control. If the mean relative viability after 4 hours of exposure is below 35% of the negative control, the test item is considered to be corrosive to skin.

Following exposure to Sodium bis(trifluoromethane)sulfonimide, the mean cell viability was 132.8% compared to the negative control, which is above the threshold of 35%, therefore the test item was considered as being non-corrosive.

In conclusion, in this in vitro EPISKINTM (SM) model test with Sodium bis(trifluoromethane)sulfonimide, the results indicate that the test item is not corrosive to the skin.