2,2'-[1,2-ethanediylbis(oxy)]bis(ethanethiol)

Skin irritation / corrosion

Administrative data

Endpoint:

skin irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

Start of experimental phase: 24 June 2016; End of experimental phase: 08 August 2016. Study completion:15 September 2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

DMDO is a strong MTT reducer, this method is not suitable for its hazard identification.

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2016

Report date:

2016

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

Adopted on 28 July 2015

Deviations:

no

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

2,2'-[1,2-ethanediylbis(oxy)]bis(ethanethiol)

EC Number:

239-044-2

EC Name:

2,2'-[1,2-ethanediylbis(oxy)]bis(ethanethiol)

Cas Number:

14970-87-7

Molecular formula:

C6H14O2S2

IUPAC Name:

2,2'-[1,2-ethanediylbis(oxy)]bis(ethanethiol)

Test material form:

liquid

In vitro test system

Test system:

human skin model

Source species:

human

Cell type:

non-transformed keratinocytes

Cell source:

skin obtained from plastic surgery from a single donor

Control samples:

yes, concurrent negative control

yes, concurrent positive control

yes, concurrent MTT non-specific colour control

Amount/concentration applied:

The test item was applied as supplied in three replicates at the treatment level of 20 µL/epidermis unit, each measuring 0.38 cm2 (treatment level: 53 µL/cm2).

Duration of treatment / exposure:

An exposure time of 15 ± 0.5 minutes was allowed in a ventilated cabinet at room temperature.
Due to the non uniform distribution of the test item on the epidermidis, a redistribution on the treated tissues after an exposure time of 7 minutes was performed.

Duration of post-treatment incubation (if applicable):

A 42 ± 1 hour recovery period was allowed by incubation at 37°C, 5 % CO2 and saturated humidity.

Number of replicates:

Negative control (live tissue): 3 replicates
Positive control (live tissue): 3 replicates
Test item (live tissue): 3 replicates
Negative control (killed tissue): 2 replicates
Test item (killed tissue): 2 replicates

Results and discussion

In vitro

Results

Remarks on result:

other: DMDO is a strong MTT reducer, this method is not suitable for its hazard identification.

Other effects / acceptance of results:

The mean cell viability of the test item, with only OD-blank subtraction, was 69 % of the concurrent negative control value, with an acceptable variability between replicates (SD of % viability = 6.3 lower than 18); however, the NSMTT control was 110 %, higher than the acceptability criteria stated in the OECD guideline n.439.

Applicant's summary and conclusion

Interpretation of results:

study cannot be used for classification

Conclusions:

The potential of the test item to be irritant to the skin was investigated through an in vitro skin irritation study, using a commercial reconstructed human epidermis (RhE) model named EPISKIN™. The blank, negative and positive controls gave acceptable results and the study was accepted as valid. Since the test item is a strong MTT reducer, this method is not suitable for its hazard identification.

Executive summary:

The potential of DMDO to be irritant to the skin was investigated through an in vitro skin irritation study using a commercial reconstructed human epidermis (RhE) model named EPISKIN™. The experimental procedures are based on the OECD Guideline for testing of chemicals no. 439. The test item, as well as controls, were tested for their ability to impair cell viability after an exposure period of 15 minutes followed by a 42 ± 1 hour recovery period. The final endpoint of the assay is the colorimetric measurement of MTT reduction (blue formazan salt) in the test system being this reaction an index of cell viability. The test item was tested as supplied by the Sponsor. Before the Main Assay, a preliminary test was carried out to evaluate the compatibility of the test item with the test system. In a first step, the test item was assayed for the ability of reducing MTT per se. A dark violet solution was noticed at the end of the incubation period, indicating that the test item can interact with MTT. Based on this result, an additional control was added in the Main Assay. In a second step, the test item was assayed for the ability of colouring water per se. No colour change was observed; spectral analysis of the test item in water, to evaluate the ability of the test chemical to absorb light at 595 nm, was performed. The value obtained for the Optical Density (OD) was 0.068, indicating that the test item does not have a potential interfering ability. In the Main Assay, the test item was applied as supplied in three replicates at the treatment level of 20 µL/epidermis unit, each measuring 0.38 cm2 (treatment level: 53 µL/cm2). Positive and negative controls [a 5 % (w/v) sodium dodecyl sulphate solution in water and Dulbecco’s phosphate buffered saline (D-PBS), respectively] were concurrently tested, in the same number of replicates and test conditions at the treatment level of 20 µL/epidermis unit. In order to verify if the test item results had to be corrected, the non specific MTT reduction (NSMTT) was evaluated using two killed tissues and compared with negative control performed with alive tissues. In the Main Assay, the negative control gave the expected baseline value (Optical Density values of the three replicates higher than 0.6) and variability [Standard Deviation (SD) of % viability lower or equal to 18], in agreement with the guideline indications. According to the method, the negative control mean value is considered the baseline value of the experiment and thus represents 100% of cell viability. The positive control caused the expected cell death (10.0 % of cell viability when compared to the negative control) and variability (SD of % viability equal to 0.5). Based on the stated criteria (mean viability = 40% and SD of % viability = 18), the assay was regarded as valid. The mean cell viability of the test item was 69 %, with an acceptable variability between replicates (SD of % Variability = 6.3). However, the NSMTT was 110 % of the concurrent negative control with alive tissues. This result indicated that the test item strongly interacts with MTT. These results do not allow a proper assessment of the irritation properties of the test item, indicating that the test method is not suitable for its hazard identification.