Tripotassium hexacyanocobaltate

Skin irritation / corrosion

Administrative data

Endpoint:

skin irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2017-01-04 to 2017-02-03

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2017

Report date:

2017

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

2015-07-28

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

signed 2015-09-14

Test material

Test material information

Constituent 1

Reference substance name:

Tripotassium hexacyanocobaltate

EC Number:

237-742-1

EC Name:

Tripotassium hexacyanocobaltate

Cas Number:

13963-58-1

Molecular formula:

C6CoN6.3K

IUPAC Name:

tripotassium hexacyanocobaltate

Test material form:

solid: particulate/powder

Details on test material:

- Physical state: bright yellow powder

Specific details on test material used for the study:

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: at room temperature

In vitro test system

Test system:

human skin model

Source species:

human

Cell type:

other: normal, human-derived epidermal keratinocytes

Cell source:

other: humans

Source strain:

not specified

Details on animal used as source of test system:

not applicable

Justification for test system used:

In an international prevalidation study performed by ECVAM, the in vitro skin irritation test using the human skin model EpiDerm™ and measurement of cell viability by dehydrogenase conversion of MTT into a blue formazan salt have turned out as a sufficiently promising predictor for skin irritancy potential.

Vehicle:

other: Dulbecco's phosphate buffered saline

Details on test system:

RECONSTRUCTED HUMAN EPIDERMIS (RHE) TISSUE
- Model used: EpiDerm™ skin model (source: MatTek Corporation, 82105 Bratislava, Slovakia)
- Tissue lot number: 23390
- Delivery date: 2017-01-31

TEMPERATURE USED FOR TEST SYSTEM
- Temperature of pre-incubation: 37 ± 1.5 °C (approx. 23 hours)
- Temperature used during treatment / exposure: 37 ± 1.5 °C for 35 minutes, room temperature for 25 minutes
- Temperature of post-treatment incubation: 37 ± 1.5 °C

REMOVAL OF TEST MATERIAL AND CONTROLS
After the end of the treatment interval the inserts were rinsed with DPBS at least 15 times in order to remove any residual test material.

After the rinsing the inserts were submerged in DPBS at least three times. Afterwards the inserts were again rinsed with DPBS. The tissues were then transferred into plates with assay medium. Tissues were incubated for about 24 hours at 37 ± 1.5 °C, 5 ± 0.5 % CO2. After incubation medium will be changed (pre-warmed fresh medium). Thereafter tissues were incubated for another 18 hours at 37 ± 1.5 °C, 5 ± 0.5 % CO2. The complete incubation time was approx. 42 hours.

MTT DYE USED TO MEASURE TISSUE VIABILITY AFTER TREATMENT / EXPOSURE
- MTT concentration: 1 mg/mL (300 µL/ well)
- Incubation time with MTT: 3 hours
- Extraction of Formazan: after the incubation period, the tissues were rinsed three times with DPBS. The tissues were transferred into new plates containing extractant solution (isopropanol) in each well ensuring that the tissues were completely covered and the plate was sealed to inhibit the isopropanol evaporation. The formazan salt was extracted for about 2 hours while shaking at room temperature.
After the extraction period was completed, the inserts were pierced with an injection needle to allow the extract to run into the well from which the insert was taken and the insert was discarded. The 24-well plates were placed on a shaker for 15 minutes until the solution was homogeneous in colour.
Per each tissue, 3 × 200 μL aliquots of the blue formazan solution were transferred into a 96-well flat bottom microtiter plate from the 15 minutes exposure. The optical density was determined with a spectrophotometer. Mean values were calculated from the 3 wells per tissue.
- Spectrophotometer: Versamax® Molecular Devices
- Wavelength: 570 nm

TEST FOR COLOUR INTERFERENCE
Before the test started, functional check for colour interference was performed. 25 ± 2 mg of the test item were added to deionised water. The mixture was incubated in the incubator (37 ± 1.5 °C, 5 ± 0.5 % CO2) for 60 minutes. At the end of the exposure time, the mixture was shaken and the presence and intensity of the staining (if any) was evaluated.

TEST FOR DIRECT MTT REDUCTION
The test item was evaluated for its potential to interfere with MTT assay. To test if a test item directly reduces MTT, 25 ± 2 mg of the test item were added to 1 mL of the MTT-solution (1mg/mL) and was incubated in the incubator (37 ± 1.5 °C, 5 ± 0.5% CO2) for 60 minutes. Untreated MTT medium was used as control.

FUNCTIONAL MODEL CONDITIONS WITH REFERENCE TO HISTORICAL DATA
- Viability: tissues pass analysis for tissue viability
- Barrier function: tissues pass analysis for tissue functionality
- Morphology: presence of a functional stratum corneum, a viable basal cell layer, and intermediate spinous and granular layers
- Contamination: absence of bacteria, yeast, and other fungi (long term antibiotic, antimycotic free culture) as well as absence of HIV1- virus, Hepatitis B virus, and Hepatitis C virus
Please also refer to the field "Attached background material" below.

PREDICTION MODEL / DECISION CRITERIA
The mean optical density (OD) of the three negative control tissues was calculated after blank correction. This value corresponds to 100% tissue viability in the current test. For each individual tissue treated with the test item or the positive control the individual relative tissue viability is calculated according to the following formula: relative viability(%) = (mean OD test item or positive control/ mean OD of negative control) x 100
For the test item and the positive control, the mean relative viability ± relative standard deviation of the three individual tissues was calculated and used for classification according to the following prediction model: if the mean relative tissue viability of three individual tissues is less or equal to 50% of the negative control, the test item needs to be classified and labeled for its skin irritauion potential: Category 2 – irritant, H315 according to Regulation (EC) No 1272/2008.

Control samples:

yes, concurrent negative control

yes, concurrent positive control

Amount/concentration applied:

TEST MATERIAL
- Amount(s) applied (volume or weight with unit): approx. 25 mg of the test item, wetted with vehicle

VEHICLE
- Amount(s) applied (volume or weight with unit): 25 µL DPBS
- Lot no.: 23308

NEGATIVE CONTROL
- Amount(s) applied (volume or weight): 30 µL DPBS

POSITIVE CONTROL
- Amount(s) applied (volume or weight): 30 µL of a 5% Sodium Lauryl Sulfate (SLS) solution

Duration of treatment / exposure:

60 minutes

Duration of post-treatment incubation (if applicable):

approx. 42 hours

Number of replicates:

triplicates

Results and discussion

In vitro

Results

Irritation / corrosion parameter:

% tissue viability

Remarks:

(mean)

Value:

102.3

Vehicle controls validity:

not examined

Negative controls validity:

valid

Positive controls validity:

valid

Other effects / acceptance of results:

- OTHER EFFECTS:
- Colour interference with MTT: the test item did not dye water and did not change colour in the presence of water. An additional test with viable tissues (but without MTT addition) was not necessary to be performed.
- Direct-MTT reduction: the MTT solution did not turn blue/purple, the test item was not considered to reduce MTT and an additional test with freeze-killed tissues did not have to be performed.

ACCEPTANCE OF RESULTS:
- Acceptance criteria met for negative control: after treatment with the negative control, the absorbance values (1.522, 1.439, and 1.509 (mean: 1.490)) were well within the required acceptability criterion of mean OD ≥ 0.8 and ≤ 2.8 for the 60 minutes treatment interval.
- Acceptance criteria met for positive control: treatment with the positive control induced a decrease in the relative absorbance as compared to the negative control to 2.2 % (acceptability criterion: positive control is ≤ 20 %).
- Acceptance criteria met for variability between replicate measurements: the relative standard deviations between the % variability values of the test item, the positive and negative controls in the main test were below 10 % (threshold of the "OECD Guideline for the Testing of Chemicals 439: In vitro Skin Irritation: Reconstructed Human Epidermis Test Method”: < 18%).
Please refer to the field "Any other information on results incl. tables" below

Any other information on results incl. tables

HISTORICAL DATA

Positive Control		Negative Control [OD570]
Mean Viability	4.37%	Mean Absorption	1.74
Rel. Standard Deviation	21.60%	Rel. Standard Deviation	9.40%
Range of Viabilities	2.20% - 6.78%	Range of Absorbance	1.34– 2.00
Mean Absorption	0.08
Rel. Standard Deviation	20.12%
Range of Absorbance	0.03 - 0.11

Data of 103 studies performed from July 2015 until March 2017

Table 1: Results after treatment with potassium hexacyanocobaltate and the controls

Dose Group	Tissue No.	Absor-bance 570 nm Well 1	Absor-bance 570 nm Well 2	Absor-bance 570 nm Well 3	Mean Absor-bance of 3 Wells	Mean-Absorbance of three wells blank corrected	Mean Absorbance of 3 tissues after blank correction	Mean Rel. Absorbance [% of Negative Control]*
Blank		0.038	0.037	0.036	0.037	0.000
Negative Control	1	1.548	1.559	1.570	1.559	1.522	1.490	100.0
	2	1.468	1.479	1.480	1.476	1.439
	3	1.545	1.546	1.548	1.546	1.509
Positive Control	1	0.064	0.069	0.068	0.067	0.030	0.033	2.2
	2	0.074	0.073	0.074	0.073	0.037
	3	0.071	0.070	0.070	0.070	0.033
Test Item	1	1.503	1.505	1.511	1.506	1.469	1.525	102.3
	2	1.458	1.454	1.456	1.456	1.419
	3	1.747	1.725	1.696	1.722	1.686

* relative absorbance per treatment group [rounded values]: 100 x (mean absorbance (test item/ positive control))/ (mean absorbance (negative control))

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met

Conclusions:

The test item is not irritating to the skin.
According to the Regulation (EC) No 1272/2008 and subsequent regulations, the test item is not irritating to the skin.