Effect of Frozen Human Epidermis Storage Duration and Cryoprotectant on Barrier Function Using Two Model Compounds

Area of Science:

• Pharmacology
• Materials Science
• Dermatology

Background:

• Human skin is frequently stored frozen for in vitro permeation experiments.
• Previous research on the effects of frozen storage on skin barrier properties has yielded conflicting results.

Purpose of the Study:

• To determine if frozen storage affects the barrier properties of human skin.
• To evaluate the cryoprotective effect of glycerol during skin freezing.

Main Methods:

• Measured steady-state flux and lag time of diethyl phthalate (DEP) through fresh and frozen human skin (-85°C for up to 18 months) with 10% glycerol.
• Assessed the impact of glycerol by comparing DEP and caffeine permeation through skin stored with and without 10% glycerol for up to 12 months.

Main Results:

• No significant differences in steady-state flux were observed between fresh and frozen skin samples (p = 0.6).
• While lag time showed a significant difference among all groups (p = 0.002), comparisons with fresh skin were not significant.
• Glycerol did not significantly affect steady-state flux or lag time for DEP or caffeine permeation (p ≥ 0.17).

Conclusions:

• Frozen human skin maintains its barrier properties for passive chemical permeation studies.
• Glycerol does not appear to offer a significant cryoprotective benefit for skin barrier function in this context.
• Frozen skin is a viable alternative to fresh skin for in vitro permeation research when viability and metabolism are not primary concerns.