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Toxicological information

Skin irritation / corrosion

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Administrative data

Endpoint:
skin irritation: in vitro / ex vivo
Type of information:
experimental study
Adequacy of study:
key study
Study period:
2016
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2017

Materials and methods

Test guideline
Qualifier:
according to
Guideline:
OECD Guideline 439 (In Vitro Skin Irritation: Reconstructed Human Epidermis Test Method)
Deviations:
yes
Remarks:
please see principles of method if other than guideline for details on deviations.
Principles of method if other than guideline:
The standard deviation of the relative individual viabilities for the three test item treated tissues was 19.5% which was slightly higher than the assay acceptance criterion of 18%. However, as all three tissues gave an unequivocal negative result it was deemed unnecessary to repeat the test.
GLP compliance:
yes (incl. certificate)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Test material form:
solid
Specific details on test material used for the study:
Identification: 2-Propenoic acid, 2-[[(octadecylamino)carbonyl]oxy]ethyl ester
Purity: >98%
Physical state/Appearance: White solid
Expiry Date: 20 June 2017
Storage Conditions: Room temperature in the dark

In vitro test system

Test system:
human skin model
Source species:
human
Cell type:
non-transformed keratinocytes
Vehicle:
unchanged (no vehicle)
Details on test system:
Main Test
Application of Test Item and Rinsing (Day 1)
2 mL of maintenance medium, warmed to approximately 37C, was pipetted into the second column of 3 wells of the 12 well plate.

Triplicate tissues were treated with the test item for an exposure period of 15 minutes. The test item was applied topically to the corresponding tissues ensuring uniform covering. 5 µL of sterile distilled water was topically applied to the epidermal surface in order to improve contact between the test item and the epidermis. Approximately 10 mg (26.3 mg/cm2) of the test item was then applied to the epidermal surface. Triplicate tissues treated with 10 µL of DPBS served as the negative controls and triplicate tissues treated with 10 µL of SDS 5% w/v served as the positive controls. To ensure satisfactory contact with the positive control item the SDS solution was spread over the entire surface of the epidermis using a pipette tip (taking particular care to cover the center). After a 7 Minute contact time the SDS solution was re spread with a pipette tip to maintain the distribution of the SDS for the remainder of the contact period (re-spreading is not required for the negative control or test item). The plates were kept in the biological safety cabinet at room temperature for 15 minutes.

At the end of the exposure period, each tissue was removed from the well using forceps and rinsed using a wash bottle containing DPBS with Ca++ and Mg++. Rinsing was achieved by filling and emptying each tissue insert for approximately 40 seconds using a constant soft stream of DPBS to gently remove any residual test item. The rinsed tissues were transferred to the second column of 3 wells containing 2 mL of maintenance medium in each well. The rinsed tissues were incubated at 37C, 5% CO2 in air for 42 hours.

MTT Loading/Formazan Extraction (Day 3)
Following the 42 Hour post-exposure incubation period each 12-well plate was placed onto a plate shaker for 15 minutes to homogenize the released mediators in the maintenance medium. 1.6 mL of the maintenance medium from beneath each tissue was transferred to pre labeled micro tubes and stored in a freezer at 14 to 30 ºC for possible inflammatory mediator determination.
2 mL of a 0.3 mg/mL MTT solution, freshly prepared in assay medium, was pipetted into the third column of 3 wells of the 12-well plates. The tissues were transferred to the MTT filled wells, being careful to remove any excess maintenance medium from the bottom of the tissue insert by blotting on absorbent paper. The tissues were incubated for 3 hours at 37 °C, 5% CO2 in air. At the end of the 3 Hour incubation period each tissue was placed onto absorbent paper to dry. A total biopsy of the epidermis was made using the EPISKINTM biopsy punch. The epidermis was carefully separated from the collagen matrix using forceps and both parts (epidermis and collagen matrix) placed into labeled 1.5 mL micro tubes containing 500 µL of acidified isopropanol, ensuring that both the epidermis and collagen matrix were fully immersed. Each tube was plugged to prevent evaporation and mixed thoroughly on a vortex mixer. The tubes were refrigerated at 1 to 10 °C until Day 6 of the experiment, allowing the extraction of formazan crystals out of the MTT-loaded tissues.

Absorbance/Optical Density Measurements (Day 6)
At the end of the formazan extraction period each tube was mixed thoroughly on a vortex mixer to produce a homogenous colored solution.

For each tissue, duplicate 200 µL samples were transferred to the appropriate wells of a pre labeled 96 well plate. 200 µL of acidified isopropanol alone was added to the two wells designated as ‘blanks’. The optical density was measured (quantitative viability analysis) at 562 nm (without a reference filter) using the Anthos 2001 microplate reader.
Control samples:
yes, concurrent negative control
yes, concurrent positive control
Amount/concentration applied:
Approximately 10 mg (26.3 mg/cm2) of the test item was then applied to the epidermal surface.
Duration of treatment / exposure:
15 minutes

Results and discussion

In vitro

Results
Irritation / corrosion parameter:
% tissue viability
Value:
83.6
Negative controls validity:
valid
Positive controls validity:
valid
Remarks on result:
no indication of irritation

Any other information on results incl. tables

Direct MTT Reduction

The MTT solution containing the test item did not turn blue or purple which indicated that the test item did not directly reduce MTT. 

Assessment of Color Interference with the MTT endpoint

The solution containing the test item was a white color. This color was attributed to the intrinsic color of the test item itself. It was therefore unnecessary to run color correction tissues.

Applicant's summary and conclusion

Interpretation of results:
GHS criteria not met
Conclusions:
The test item was classified as non-irritant.