Reaction mass of 1,1,1,5,5,5-hexamethyl-3-phenyl-3-((trimethylsilyl)oxy)trisiloxane and 1,1,1,7,7,7-hexamethyl-3,5-diphenyl-3,5-bis[(trimethylsilyl)oxy]tetrasiloxane and 1,1,1,9,9,9-hexamethyl-3,5,7-triphenyl-3,5,7-tris((trimethylsilyl)oxy)pentasiloxane

Dermal absorption

Administrative data

Endpoint:

dermal absorption in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

disregarded due to major methodological deficiencies

Study period:

9-12 August 1999 (pig skin) and 22-25 September 1999 (human skin)

Reliability:

3 (not reliable)

Rationale for reliability incl. deficiencies:

significant methodological deficiencies

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2001

Report date:

2001

Materials and methods

Test guideline

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 428 (Skin Absorption: In Vitro Method)

Deviations:

yes

Remarks:

(technical difficulties prevented a reliable result from being obtained)

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Radiolabelling:

no

Test animals

Species:

other: human abdominal skin and pig hind-leg skin

Strain:

not specified

Sex:

female

Details on test animals or test system and environmental conditions:

In vitro test

Administration / exposure

Type of coverage:

open

Vehicle:

unchanged (no vehicle)

Duration of exposure:

2, 4, 6, 8, 10, 20 and 24 hours

Doses:

10 µl undiluted test material (9.8 mg)/cm2 (or per 0.64 cm2 - study report cites both)

No. of animals per group:

In vitro study: 5 human skin and 5 pig skin replicates

Control animals:

yes

Remarks:

in vitro study: tritiated water and testosterone

Details on study design:

In vitro test

Details on in vitro test system (if applicable):

SKIN PREPARATION
- Source of skin:
- human skin was obtained from one female Caucasian donor of 39 years old after abdominal surgery
- pig skin was obtained from the hind legs of one young female domestic pig (Hollands Landvarken, University of Utrecht) of approx. 30 kg bw directly after sacrifice of the animal
- Ethical approval if human skin: yes
- Type of skin: abdominal (human), hind-leg (pig)
- Preparative technique: briefly, sterile glass rings (internal area 0.64 cm2) were glued to the skin membranes using cyanoacrylate-based glue. Skin membranes were washed 3 times for 15 min in medium supplemented with bactericides and fungicides. The skin membranes were transferred into 6-well plates on a Netwell insert (200 µm mesh), which allows contact of the receptor fluid to the dermal side of the skin, while the stratum coneum remains exposed to the air
- Thickness of skin (in mm): 0.57± 0.03 mm (human); 0.56± 0.03 mm (pig)
- Membrane integrity check: yes
- Storage conditions: on ice
- Justification of species, anatomical site and preparative technique: no data

PRINCIPLES OF ASSAY
- Diffusion cell: 6-well plates
- Receptor fluid: mixture of Dulbecco's Modified Essential Medium and Ham F12 culture medium (2:1) supplemented with Epidermal Growth Factor (10 µg/l), hydrocortisone (400 µg/l, gentamicin (50 mg/l), polyoxyethylene 20 oleyl ether (6%, w/v) and Foetal Calf Serum (10%, v/v)
- Solubility of test substance in receptor fluid: no data
- Static system: yes
- Flow-through system: no
- Test temperature: 32 °C
- Humidity: humidified incubator
- Occlusion: no
- Reference substance(s): water, testosterone

Results and discussion

Signs and symptoms of toxicity:

not examined

Dermal irritation:

not examined

Absorption in different matrices:

- Receptor fluid, receptor chamber, donor chamber (in vitro test system): due to analytical problems, receptor fluid (human skin) was not analysed for the presence of trimethylsilyloxy phenyl silsesquioxane; receptor fluid (pig skin) analysed
- Skin preparation (in vitro test system): due to analytical problems, skin membranes (human and pig skin) were not analysed for the presence of trimethylsilyloxy phenyl silsesquioxane

Total recovery:

- Total recovery: On cotton swab used to wipe exposure site: 35.1-174.3% (human skin); 30.1 to 107.4% (pig skin)
- Recovery of applied dose acceptable: no
- Results adjusted for incomplete recovery of the applied dose: not applicable
- Limit of detection (LOD): 2 mg/l
- Quantification of values below LOD or LOQ: no

Percutaneous absorption

Dose:

10 µl (9.8 mg)

Parameter:

percentage

Absorption:

< 0.1 %

Remarks on result:

other: 24 hours

Remarks:

pig skin: below the limit of detection (2 mg/l extract, 4 µg/l receptor fluid) at all timepoints; no data for human skin due to technical difficulties )

Any other information on results incl. tables

In the study, the analysis of the various samples for the presence of the test material was not successful, mainly due to recurring high background values. Because of these technical difficulties, it was decided to terminate the study.

Applicant's summary and conclusion

Conclusions:

In a GLP study, conducted using a protocol similar to OECD test guideline 428, the dermal absorption of trimethylsilyloxy phenyl silsesquioxane was evaluated in vitro in human and pig skin. For pig skin, dermal absorption was <0.1% but, due to technical difficulties, the result should be interpreted with caution. No results were reported for human skin.

Executive summary:

In a GLP study, conducted using a protocol similar to OECD test guideline 428, the percutaneous absorption of trimethylsilyloxy phenyl silsesquioxane was evaluated in human and pig skin membranes in vitro.

The test material was applied at about 9.8 mg/cm2 and samples of receptor fluid collected periodically over 24 hours. Due to technical difficulties, no reliable analysis of the samples for the presence of the test material was possible and the study was terminated. Some data were generated, which the investigators recommended should be interpreted with caution.

In the pig skin assay, trimethylsilyloxy phenyl silsesquioxane was present at a level below the limit of detection (2 mg/l extract corresponding to 4 µg/ml receptor fluid) at all time points, indicating absorption of <0.1%. Receptor fluid in the human skin assay was not analysed due to technical difficulties.

No reliable results for dermal absorption were obtained from this study.