N,N'-diphenyl-p-phenylenediamine

Skin irritation / corrosion

Administrative data

Endpoint:

skin irritation: in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

01 Mar 2016 to 22 Mar 2016

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2016

Report date:

2016

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

28 July 2015

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method B.46 (In Vitro Skin Irritation: Reconstructed Human Epidermis Model Test)

Version / remarks:

6 July 2012

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

N,N'-diphenyl-p-phenylenediamine

EC Number:

200-806-4

EC Name:

N,N'-diphenyl-p-phenylenediamine

Cas Number:

74-31-7

Molecular formula:

C18H16N2

IUPAC Name:

N,N'-diphenyl-p-phenylenediamine

Test material form:

solid

Specific details on test material used for the study:

SOURCE OF TEST MATERIAL
- Test-substance No.: 16/0045-1
- Batch identification: 20150925
- Purity test date: 82.5 %
- Physical state / colour: solid / grey to brown

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

In vitro test system

Test system:

human skin model

Remarks:

EpiDermTM model

Source species:

human

Cell type:

non-transformed keratinocytes

Cell source:

other: cultured

Vehicle:

unchanged (no vehicle)

Remarks:

solid was homogeneously distributed with PBS (1:1 v/v)

Details on test system:

MATERIALS AND TECHNICAL EQUIPMENT
- Laminar flow bench: HERAsafe KS 18 (Thermo ELECTRON CORPORATION)
- CO2 incubator: Heraeus BBD 6220
- Incubation conditions: 37°C ± 1°C, 5% ± 1% CO2, 90% ± 5% humidity
- Spectrophotometer: SunriseTM Absorbance Reader For the determination of the optical density of colored extracts. Measurement using a filter wavelength 570 nm without reference filter
- EpiDerm™ 200 kit: MatTek In Vitro Life Science Laboratories, Bratislava, Slovakia; containing: 24 EPI-200 tissues (reconstructed epidermis): surface 0.6 cm² cultured in Millicells® ø 1 cm
- Tissue for MTT reduction control: EPI-200 tissue that is killed by freezing at –20°C
- Assay medium: EPI-100-NMM assay medium
- MTT diluent: Dulbecco's modified eagle's medium (DMEM) based medium used for diluting MTT (MatTek In Vitro Life Science Laboratories, Bratislava, Slovakia / Sigma, Germany)
- Wash buffer: Dulbecco's phosphate buffered saline (PBS), w/o Ca 2+, Mg 2+ (MatTek In Vitro Life Science Laboratories, Bratislava, Slovakia and Biochrom, Germany)
- Detection agent: 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) (MatTek In Vitro Life Science Laboratories, Bratislava, Slovakia / Sigma, Germany), 1.0 mg / mL MTT diluent
- Extracting agent: Isopropanol p.a.

TEST SYSTEM
The EpiDermTM model consists of normal, human-derived epidermal keratinocytes which have been cultured to form a multi layered, highly differentiated model of the human epidermis. It consists of organized basal, spinous and granular layers, and a multi-layered stratum corneum containing intercellular lamellar lipid layers arranged in patterns analogous to those found in vivo. The EpiDermTM tissues (surface 0.6 cm²) are cultured on specially prepared cell culture inserts (MILLICELLs®, 10 mm ø) and commercially available as kits (EpiDerm™ 200), containing 24 tissues on shipping agarose.
- Tissue model: EPI-200
- Tissue Lot Number: 23317
- Origin: MatTek In Vitro Life Science Laboratories, Bratislava, Slovakia

DIRECT MTT REDUCTION
- The direct reduction of MTT by a test substance interferes with the color density produced by metabolic capacity of the tissue and would falsify the test results.
- To assess the ability of the test material to directly reduce MTT a pretest (experimental conduct in accordance with GLP but without a GLP status) was performed as described below.
- The test substance was added to 0.9 mL of the MTT solution. The mixture was incubated in the dark at about 37 °C for 3 hours. A negative control (de-ionized water) was tested concurrently. If the color of the MTT solution or, in case of water-insoluble test substances the border to the water-phase, turned blue / purple, the test substance was presumed to directly reduce MTT.
- In case that direct MTT reduction occurred, three freeze-killed control tissue (KC) were treated with the test article and the negative control

BASIC PROCEDURE
- Several test substances were tested in parallel within the present test using the same control tissues (negative control, NC and positive control, PC).
- On the day of arrival in the laboratory, the tissues were transferred to sterile 6-well plates with 0.9 mL assay medium and preconditioned in the incubator at 37°C. After 1 hour the preincubation medium was replaced with fresh medium and preconditioning continued for 18 ± 3 hours.
- Three tissues were treated with the test substance, the PC and NC, respectively. In addition three killed control tissues were used for the test substance and NC, respectively, in order to detect direct MTT reduction.
- 25 μL sterile PBS was applied first. Thereafter, a bulk volume of ca. 25 μL of the solid test material was applied with a sharp spoon and homogeneously distributed together with the fluid.
- Control tissues were concurrently treated with 30 μL of sterile PBS (NC, NC KC)) or with 30 μL of 5% SDS (PC) or test substance (KC). A nylon mesh was placed carefully onto the tissue surface of the NC, NC KC and PC afterwards.
- The tissues were kept under the laminar flow hood at room temperature for 25 minutes overall and for 35 minutes in the incubator.
- The tissues were washed with sterile PBS to remove residual test material 1 hour after start of application. Rinsed tissues were blotted on sterile absorbent paper and transferred into new 6- well plates, pre-filled with 0.9 mL fresh medium. When all tissues were rinsed, the surface of each tissue was carefully dried with a sterile cotton swab.
- Subsequently, the tissues were placed into the incubator at 37°C for 24 ± 2 hours.
- After 24 ± 2 hours the tissues were transferred into new 6-well plates pre-filled with 0.9 mL of fresh medium and placed into the incubator for additional 18 ± 2 hours post-incubation period.
- After the post-incubation period, the assay medium was replaced by 0.3 mL MTT solution and the tissues were incubated in the incubator for 3 hours.
- After incubation, the tissues were washed with PBS to stop the MTT-incubation. The formazan that was metabolically produced by the tissues was extracted by incubation of the tissues in isopropanol. The optical density at a wavelength of 570 nm (OD570) of the extracts was determined spectrophotometrically. Blank values were established of 4 microtiter wells filled with isopropanol for each microtiter plate.

DATA EVALUATION
- Principle: The OD570 values determined for the various tissues are measures of their viability. The quotient of the OD570 of tissues treated with the test material and the mean OD570 values of the NC (percent of control) is used for evaluating whether or not a test material is irritant.
- Calculation of individual and mean optical densities: The individual tissue OD570 is calculated by subtracting the mean blank value of the respective microtiter plate from the respective individual tissue OD570 value. The mean OD570 for a test group of three tissues treated in the same way is calculated.
- Application of measurements using killed control tissues: In case of direct reduction of MTT by the test substance, the OD570 values measured in the freeze-killed control tissues (KC) will be used to correct the mean OD570 of the test-substance treated tissues (mean OD570 KC corrected). Since killed tissue might still have a residual enzyme activity that is able to produce some formazan net OD570 KC is calculated by subtracting the OD570 KC of the NC from the OD570 KC of the test substance. In case the net OD570 KC is greater than zero it is subtracted from the respective mean OD570 to result in the mean OD570 KC corrected. The mean OD570 KC corrected represents the formazan production linked to the tissue viability and therefore indicates the cytotoxic potency of the test substance.
- Tissue viability: The quantification of tissue viability is presented as the quotient of the mean OD570 (or mean OD570 KC corrected, if applicable) divided by the respective OD570 NC value in percent for each exposure time.

ACCEPTANCE CRITERIA
In case one of the below given acceptance criteria was not met, repetition of the test was considered.
- Barrier function and Quality control (QC): The supplier demonstrates that each batch of the model used meets the defined production release criteria. MatTek determines the ET50 value following exposure to Triton X-100 (1%) for each EpiDermTM batch. The ET50 must fall within a range established based on a historical database of results. The following acceptability range (upper and lower limit) for the ET50 is established by the supplier as described in the cited OECD guidelines. Lower acceptance limit: ET50 = 4.0 hours; Upper acceptance limit: ET50 = 8.7 hours
- Acceptance criteria for the negative control (NC): The absolute OD570 of the negative control tissues in the MTT test is an indicator of tissue viability obtained in the testing laboratory after the shipping and storing procedure and under specific conditions of the assay. Tissue viability is acceptable if the mean OD570 of the NC is ≥ 0.8. The mean OD570 of the NC should not exceed 2.8.
- Acceptance criteria for the positive control (PC): 5% SDS is used as PC and reflects the sensitivity of the tissues used in the test conditions. A viability of ≥ 20% is acceptable.
- Acceptance criteria for the variability of the tissues: For every treatment three tissues are treated in parallel. The inter-tissue variability is considered to be acceptable if the SD of %-viability is ≤ 18%.
- Acceptance criteria for the killed controls (KC): The OD570 of the tissues for the KC of the NC should be ≤ 0.35. The OD570 value for direct MTT-reduction of a test substance should be ≤ 30% of the OD570 of the NC.

EVALUATION OF RESULTS
- Irritant potential of the test materials is predicted from the mean relative tissue viabilities compared to the negative control tissues concurrently treated with sterile PBS. A chemical is considered as "irritant", if the mean relative tissue viability with a test material is less than or equal to 50%.
- A single test composed of at least three tissue replicates should be sufficient for a test chemical when the result is unequivocal. However, in cases of borderline results, such as non-concordant replicate measurements and/or mean percent tissue viability equal to ±5% of the cut-off value, a second test should be considered, as well as a third one in case of discordant results between the first two tests.

Control samples:

yes, concurrent negative control

yes, concurrent positive control

yes, concurrent MTT non-specific colour control

Amount/concentration applied:

TEST MATERIAL
25 μL sterile PBS was applied first. Thereafter, a bulk volume of ca. 25 μL of the solid test material was applied with a sharp spoon and homogeneously distributed together with the fluid.

CONTROLS
Control tissues were concurrently treated with 30 μL of sterile PBS (NC, NC KC) or with 30 μL of 5% SDS (PC) or test substance (KC).

Duration of treatment / exposure:

1 hour

Duration of post-treatment incubation (if applicable):

43 hour post-incubation period

Number of replicates:

3 replicates

Results and discussion

In vitro

Results

Irritation / corrosion parameter:

% tissue viability

Run / experiment:

Irritation test: 1 hour exposure

Value:

110.7

Vehicle controls validity:

not applicable

Negative controls validity:

valid

Positive controls validity:

valid

Other effects / acceptance of results:

ACCEPTANCE OF RESULTS:
- Acceptance criteria for negative control are met.
- Acceptance criteria for positive control are met.
- Acceptance criteria for variability between replicate measurements are met.

Applicant's summary and conclusion

Interpretation of results:

GHS criteria not met

Remarks:

In combination with skin corrosion results (OECD 431)