Build a solid foundation in science, formulation and product development—find out more!
Most Popular in:
In Vitro Model for Decontamination of Human Skin
By: Hongbo Zhai, MD, University of California; and Howard I. Maibach, MD, University of California School of Medicine
Posted: April 1, 2009, from the April 2009 issue of Cosmetics & Toiletries.
page 3 of 5
Human skin: Human cadaver skinc was dermatomed to a 500-µm thickness. Skin samples were stored in Eagle’s Minimum Essential Mediad and refrigerated at 4°C prior to use within five days after death to maintain viability.6–8 A total of five skin samples were used.
Procedure: Skin was placed onto glass diffusion cells with rubber bands. The diffusion cells had been pre-filled with a maximum amount of the receptor fluid: 0.9% sodium chloride, approximately 6 mL in each. Then, aliquots 10 µl (approximately 0.25 µg) of [14C]-formaldehyde solution was dosed by a high performance liquid chromatography syringe onto each skin surface. After exposure intervals of 1 min, 3 min, and 30 min post-dosing, the surface skin (3 cm2) was washed with 4 mL of each solution per time; thus, a total of 12 mL of each solution was used to wash off one sample. All washing liquids were collected individually into a scintillation glass vial for radioactive measurement. The skin was then stripped twice with tape discse, superficially removing chemical residue from the skin. Lastly, the remaining amounts of [14C]-formaldehyde in the wash solutions, strippings, receptor fluid and remaining skin were determined.
Evaporation test and scintillation counting: Evaporation tests monitored the percentage of [14C]-formaldehyde evaporation at exposure times of 1 min, 3 min, 15 min, 30 min and 60 min. Plastic discs, 1.75 cm in diameter and 0.178 mm thick, were each applied with 1 µCi/10 µL/cm2 of [14C]-formaldehyde and timed for the appropriate duration of exposure. Triplicates for each time point were taken, yielding a total of 15 disc samples, after which each disc sample was immediately placed into its designated scintillation vial; the vial was then filled with a pre-designated liquid compoundf.
Background control samples and the test samples were counted in a computer-controlled liquid scintillation analyzerg. Control and test sample counts were then transferred to a computer program that subtracted background control samples and generated a spreadsheet data report. The in-house counting process and the computer program were verified by a quality assurance officer.
Statistical analysis: Statistical analysis was performed utilizing a computer programh. Differences were analyzed utilizing the One Way Repeated Measures ANOVA. Statistical significance was accepted at p < 0.05.