Electrochemical monitoring of native catalase activity in skin using skin covered oxygen electrode

A skin covered oxygen electrode, SCOE, was constructed with the aim to study the enzyme catalase, which is part of the biological antioxidative system present in skin. The electrode was exposed to different concentrations of H2O2 and the amperometric current response was recorded. The observed current is due to H2O2 penetration through the outermost skin barrier (referred to as the stratum corneum, SC) and subsequent catalytic generation of O-2 by catalase present in the underlying viable epidermis and dermis. By tape-stripping the outermost skin layers we demonstrate that SC is a considerable diffusion barrier for H2O2 penetration. Our experiments also indicate that skin contains a substantial amount of catalase, which is sufficient to detoxify H2O2 that reaches the viable epidermis after exposure of skin to high concentrations of peroxide (0.5-1 mM H2O2). Further, we demonstrate that the catalase activity is reduced at acidic pH, as compared with the activity at pH 7.4. Finally, experiments with often used penetration enhancer thymol shows that this compound interferes with the catalase reaction. Health aspect of this is briefly discussed. Summarizing, the results of this work show that the SCOE can be utilized to study a broad spectrum of issues involving the function of skin catalase in particular, and the native biological antioxidative system in skin in general.