Copper dioleate

Eye irritation

Administrative data

Endpoint:

eye irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

9-12 May 2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

comparable to guideline study

Remarks:

OECD Guideline for the Testing of Chemicals, Part 492, adopted 28. Jul. 2015, “Reconstructed Human Cornea-like Epithelium (RhCE) Test Method for Identifying Chemicals Not Requiring Classification and Labelling for Eye Irritation or Serious Eye Damage”

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2016

Report date:

2017

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 492 (Reconstructed Human Cornea-like Epithelium (RhCE) Test Method for Identifying Chemicals Not Requiring Classification and Labelling for Eye Irritation or Serious Eye Damage)

Version / remarks:

adopted 28. Jul. 2015

Deviations:

yes

Remarks:

Normally, an additional pre- test should be performed, because the test item might be possibly interacting with the photometrical measurement. The missing performance of the pre-test can be seen as uncritical, because the main test was positive

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Copper dioleate

EC Number:

214-307-4

EC Name:

Copper dioleate

Cas Number:

1120-44-1

Molecular formula:

C18H34O2.1/2Cu

IUPAC Name:

copper(2+) bis((9Z)-octadec-9-enoate)

Test material form:

solid

Remarks:

paste

Details on test material:

Solid green paste. Batch number 21092015

Specific details on test material used for the study:

Name: Copper dioleate
Batch no.: 21092015
Appearance: Green, solid/paste
Composition: Cu-dioleate
Purity: > 99 %, IR
Homogeneity: homogeneous
Expiry date: 21. Sep. 2018
Storage: Room Temperature (20 ± 5°C)

Test animals / tissue source

Species:

human

Strain:

other: human-derived keratinocytes which have been cultured to form a stratified squamous epithelium similar to that found in the human cornea. It consists of highly organized basal cells.

Details on test animals or tissues and environmental conditions:

Commercially available EpiOcularTM kit.
The EpiOcularTM tissue consists of normal, human-derived keratinocytes which have been
cultured to form a stratified squamous epithelium similar to that found in the human cornea.
It consists of highly organized basal cells. These cells are not transformed or transfected
with genes to induce an extended life span. The EpiOcularTM tissues are cultured in
specially prepared cell culture inserts with a porous membrane through which nutrients
can pass to the cells. The tissue surface is 0.6 cm2.

Test system

Vehicle:

unchanged (no vehicle)

Controls:

yes, concurrent positive control

yes, concurrent negative control

Amount / concentration applied:

Tissue 1: 52.2 mg
Tissue 2: 49.1 mg

Duration of treatment / exposure:

6h

Duration of post- treatment incubation (in vitro):

For post-treatment incubation, the tissues were incubated for 18 h + 9 min at 37 ± 1 °C, 5 ± 1 % CO2 and 80 – 100 % relative humidity.

Number of animals or in vitro replicates:

2 (tissue 1&2)

Details on study design:

Pre-Tests
Assessment of Direct Reduction of MTT by the Test Item
The test item Copper dioleate was tested for the ability of direct formazan reduction. To
test for this ability, 51.7 mg of the solid test item were added to 1 mL of MTT reagent in a
6-well plate and the mixture was incubated in the dark at 37 ± 1 °C, 5 ± 1 % CO2 and 80 –
100 % relative humidity for 3 h. 1 mL of MTT reagent plus 50 μL of H2O demin. was used
as negative control.
The MTT reagent did not change its colour; therefore, direct MTT reduction had not taken
place, and no data correction was necessary.

Assessment of Coloured or Staining Test Items
51.0 mg of the test item were added to 2 mL isopropanol, incubated in 6-well plates on an orbital shaker for 2 h and 23 min at room temperature. Then, two 200 μL aliquots of the resulting solution and two 200 μL aliquots of neat isopropanol were centrifuged (1750 rpm,
30 sec) and then transferred into a 96-well plate and measured with a plate reader at 570 nm.

After subtraction of OD for isopropanol, the OD of the test item solution was 0.4995 (> 0.08). Normally, an additional test should be performed, because the test item might be possibly interacting with the photometrical measurement. But as the result of the main test was positive (“eye irritating”), a possible false negative result could be excluded and no additional test was necessary.

Main Test
Preparations
On the day of the start of the experiment, the MTT concentrate was thawed. The concentrate was diluted with the MTT solvent and the solution was used directly. The assay medium was warmed in the water bath to 37 ± 1°C. 6-well-plates were labelled with test item, resp. negative control, resp. positive control and filled with 1 mL assay medium in the appropriate wells. All 24 inserts were inspected for viability and the presence of air bubbles between agarose gel and insert. Viable tissues were transferred in the prepared 6-well-plate and incubated at 37 ± 1 °C, 5 ± 1 % CO2 and
80 – 100 % relative humidity for 1 h. After the pre-incubation, the medium was replaced and the wells were filled with 1 mL fresh assay medium. All 6-well-plates were incubated at 37 ± 1 °C, 5 ± 1 % CO2 and 80 – 100 % relative humidity for 16 h and 30 min.


Exposition and Post-Treatment
After overnight incubation, the tissues were pre-wetted with 20 μL DPBS buffer and the tissues were incubated at 37 ± 1 °C, 5 ± 1 % CO2 and 80 – 100 % relative humidity for 30 min. After that, 50 μL of the controls and a defined amount of test item were applied in duplicate. At the beginning of each experiment (application of negative controls), a stop watch was started.

After dosing the last tissue, all plates were transferred into the incubator for 6 h at 37 ± 1 °C, 5 ± 1 % CO2 and 80 – 100 % relative humidity. At the end of exposure time, the inserts were removed from the plates in 1-min-intervals using sterile forceps and rinsed immediately. The inserts were thoroughly rinsed with DPBS. Then, the tissues were immediately transferred into 5 mL of assay medium in prelabelled 12-well plate for 25 min post soak at room temperature. After that, each insert was blotted on absorbent material and transferred into a pre-labelled 6-well plate, containing 1 mL assay medium. For post-treatment incubation, the tissues were incubated for 18 h + 9 min at 37 ± 1 °C, 5 ± 1 % CO2 and 80 – 100 % relative humidity. After the post-treatment incubation, the MTT Assay was performed.


MTT Assay and Extraction
A 24-well-plate was prepared with 300 μL freshly prepared MTT-reagent in each well. The tissue inserts were blotted on absorbent material and then transferred into the MTT solution. The plate was incubated for 180 min at 37 ± 1 °C, 5 ± 1 % CO2 and 80 – 100 % relative humidity.
At last, each insert was thoroughly dried and set into a pre-labelled 6-well-plate, containing 2 mL isopropanol, taking care that no isopropanol is flowing into the tissue insert. The plate was firmly sealed to avoid evaporation of the solvent and then shaken for 2 h at room temperature.

Measurement
The inserts were removed from the 6-well plate and discarded. The content of each well was thoroughly mixed in order to achieve homogenisation.
From each well, two replicates with 200 μL solution (each) were pipetted into a 96-wellplate. Eight wells with 200 μL isopropanol were pipetted as blank. The plate was read in a plate spectrophotometer at 570 nm.

Results and discussion

In vitro

Results

Irritation parameter:

other:

Remarks:

% Viability (Tissue ) based of optical density of the MTT solution compared to control

Value:

32.3

Negative controls validity:

valid

Positive controls validity:

valid

Remarks on result:

positive indication of irritation

Other effects / acceptance of results:

Eye irritation is assessed using the criteria given in the following table (source: MatTek Corporation):
Assessment of Eye Irritation
% Viability: > 60 %
Assessment: Non eye irritant
GHS category: No GHS category


% Viability: ≤ 60 %
Assessment: Eye irritant
GHS category: GHS category 1 or 2

Validity
Criterion: OD of negative control
Demanded ≥ 0.8 and ≤ 2.5
Result: 1.9


Criterion: % Formazan production of positive control
Demanded: < 50% of negative control
Result: 36.4%


Criterion: Variation within replicates
Demanded: ≤ 20%
Results:
1.0% (negative control)
1.1% (positive control)
2.2% (test item)

The value for the positive control was within the range of historical data of the test facility (see annex 2, page 19). The value of the negative control was marginally outside the range of the historical data (see annex 2, page 19). This can be seen as uncritical, because the value was only marginally above the historical range and moreover the value was still within the accepted range of the validity criterion.
Therefore, the experiment is considered valid.
10 DISCUSSION
Under the conditions of the test system, Copper dioleate is considered as eye irritant in the EpiOcularTM Eye Irritation Test.
After treatment with the test item, the relative absorbance values were reduced to 32.3 %.
This value is below the threshold for eye irritation potential (≤ 60%).
All validity criteria were met. The criterion for optical density of the negative control was fulfilled: The OD value was 1.9 (> 0.8 and < 2.5).
The positive control induced a decrease in the relative absorbance as compared to the negative control to 36.4%. Therefore, the validity criterion that this value should be re-duced to < 50% was met.
Variation within the replicates of negative control, positive control and test item was within the accepted range (< 20 %).
For these reasons, the result of the test is considered as valid.

Applicant's summary and conclusion

Interpretation of results:

Category 2 (irritating to eyes) based on GHS criteria

Conclusions:

Under the conditions of the test system, Copper dioleate is considered as eye irritant in the EpiOcularTM Eye Irritation Test.
After treatment with the test item, the relative absorbance values were reduced to 32.3 %.
This value is below the threshold for eye irritation potential (≤ 60%).
All validity criteria were met. The criterion for optical density of the negative control was fulfilled: The OD value was 1.9 (> 0.8 and < 2.5).
The positive control induced a decrease in the relative absorbance as compared to the negative control to 36.4%. Therefore, the validity criterion that this value should be reduced to < 50% was met. Variation within the replicates of negative control, positive control and test item was within the accepted range (< 20 %).
For these reasons, the result of the test is considered as valid.

Executive summary:

One valid experiment was performed.

The test item Copper dioleate was applied to a three-dimensional human cornea tissue model in duplicate for an exposure time of 6 h. After treatment, the respective substance was rinsed from the tissue; then, cell viability of the tissues was evaluated by addition of MTT, which can be reduced to formazan. The formazan production was evaluated by measuring the optical density (OD) of the resulting solution. Demineralised water was used as negative control, Methyl acetate was used as positive control.

The controls showed the following results: After treatment with the negative control, the absorbance values were within the required acceptability criterion of 0.8 ≤ mean OD ≤ 2.5, OD was 1.9. The positive control showed clear eye irritating effects, the relative absorbance value was reduced to 36.4 % (< 50%). Variation within tissue replicates of negative control, positive control and test item was within the accepted range (≤ 20%). After treatment with the test item, the relative absorbance values were reduced to 32.3%. This value is below the threshold for eye irritation potential (≤ 60%).

Under the conditions of the test system, Copper dioleate is considered as eye irritant in the EpiOcularTM Eye Irritation Test.