1,1,5,5,5-hexamethyl-3,3-bis[(trimethylsilyl)oxy]trisiloxane

Skin irritation / corrosion

Administrative data

Endpoint:

skin irritation: in vitro / ex vivo

Remarks:

EPISKIN-SM™

Type of information:

experimental study

Adequacy of study:

key study

Study period:

22 Dec 2021 to 29 March 2022

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2022

Report date:

2022

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

2021/EPISKIN-Standard Model™

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

1,1,1,5,5,5-hexamethyl-3,3-bis[(trimethylsilyl)oxy]trisiloxane

Cas Number:

3555-47-3

IUPAC Name:

1,1,1,5,5,5-hexamethyl-3,3-bis[(trimethylsilyl)oxy]trisiloxane

Test material form:

liquid: volatile

Remarks:

colourless

In vitro test system

Test system:

human skin model

Remarks:

reconstituted three-dimensional human skin model EPISKIN-SM

Source species:

human

Cell type:

non-transformed keratinocytes

Cell source:

other: Not specified

Source strain:

other: Not applicable

Details on animal used as source of test system:

Not applicable

Justification for test system used:

This test uses the EPISKIN-Standard Model™ (EPISKIN-SM™), a reconstructed human epidermis model (EpiSkin) which consists of normal human epidermal keratinocytes (NHEK) and, therefore, represents in vitro the target organ of the species of interest and closely mimics the biochemical and physiological properties of the upper parts of the human skin, i.e., the epidermis. The EPISKIN-Standard Model™ (EPISKIN-SMTM) was used as a replacement for the Draize Skin Irritation Test (OECD TG 404) to distinguish between UN GHS “Category 2” skin irritating test substances and not categorized test substances (“No Category”) which may be considered as non-irritant.

Vehicle:

unchanged (no vehicle)

Details on test system:

RECONSTRUCTED HUMAN EPIDERMIS (RHE) TISSUE
- Model used: EPISKIN-SM™
- Tissue batch number(s): 22 EKIN 009
- Production date: not specified
- Shipping date: not specified
- Delivery date: not specified
- Date of initiation of testing: 02 February 2022

TEMPERATURE USED FOR TEST SYSTEM
- Temperature used during treatment / exposure: Room tremperature
- Temperature of post-treatment incubation (if applicable): 37±1 °C,

REMOVAL OF TEST MATERIAL AND CONTROLS
- Number of washing steps: The tissues were washed with DPBS to remove any residual test item. Excess DPBS was removed by blotting bottom with blotting paper.
- Observable damage in the tissue due to washing: None reported
- Modifications to validated SOP: None

DYE BINDING METHOD
- Dye used in the dye-binding assay: MTT
- Incubation time: 3 hours ±5 min
- Spectrophotometer: Plate spectrophotometer
- Wavelength: OD was measured at 570nm
- Filter: Filter band
- Filter bandwidth: 30nm
- Linear OD range of spectrophotometer: without reference wavelength

NUMBER OF INDEPENDENT TESTING RUNS / EXPERIMENTS TO DERIVE FINAL PREDICTION: One pre-experiment and one main experiment

PREDICTION MODEL / DECISION CRITERIA (choose relevant statement)
- The test substance is considered to be irritant to skin if the viability after 15 minutes exposure is less than 50%
- The test substance is considered to be non-irritant to skin if the viability after 15 minutes exposure is greater than or equal to 50%
- Justification for the selection of the cut-off point(s) if different than recommended in TG 431 and 439: not applicable

Control samples:

yes, concurrent negative control

yes, concurrent no treatment

Amount/concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): 10 μL (26.3 μL/cm2)
- Concentration (if solution): Undiluted (neat)

NEGATIVE CONTROL
- Amount(s) applied (volume or weight): 10 μL
- Concentration (if solution): Dulbecco's Phosphate Buffering Saline (DPBS)

POSITIVE CONTROL
- Amount(s) applied (volume or weight): 10 μL
- Concentration (if solution): 5% sodium dodecyl sulfate (SDS)

Duration of treatment / exposure:

15 minutes

Duration of post-treatment incubation (if applicable):

42 hours

Number of replicates:

Three

Results and discussion

In vitro

Results

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

Experiment 1

Value:

> 50

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

no indication of irritation

Other effects / acceptance of results:

- OTHER EFFECTS:
- Visible damage on test system: No
- Direct-MTT reduction: The test item showed no non-specific MTT reducing potential, therefore no additional controls for correction of results were necessary.
- Colour interference with MTT: The test item showed no colouring potential, therefore no additional controls for correction of results were necessary.

DEMONSTRATION OF TECHNICAL PROFICIENCY:
- Mean OD570 nm six blank values: 0.046; cut off < 0.1;
- Mean Absolute OD570 nm negative control: 0.797, cut off ≥ 0.6 and ≤1.5;
- Mean Relative Viability [% negative control] of the positive control: 12.5; cut off < 40%;
- Max. SD Viability of replicate tested tissues of all dose groups [%]: 10.8, cut off ≤ 18%

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
- Range of historical values if different from the ones specified in the test guideline: not applicable

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met

Conclusions:

In the in vitro skin irritation study with 1,1,1,5,5,5-hexamethyl-3,3-bis[(trimethylsilyl)oxy]trisiloxane (CAS 3555-47-3) conducted according to OECD 439 and in compliance with GLP using the EPISKIN-SM™ tissue model, the reported mean relative tissue viability (% negative control) was >50% (106.7%) after 15 minutes treatment and 42 hours post-incubation. The positive control produced the expected reduction in viability. The test item is therefore categorised as a 'non-irritant' ('No Category') as applicable under the CLP and UN GHS and under the conditions and limitations of the model.