Penetration of compounds through human stratum corneum as studied by Fourier transform infrared photoacoustic spectroscopy

The penetration of the lipophilic model permeant, 1-cyanodecane, into isola ted human stratum corneum (SC) was followed nondestructively by step-scan F ourier transform infrared (FTIR) photoacoustic spectroscopy (PAS) with phas e modulation technique, The uptake of the compound in the SC was quantified by monitoring the alterations in the spectra in the course of the penetrat ion using multivariate analysis. Step-scan technique in conjunction with ph ase modulation offers the possibility for controllable depth profiling (sam pling depth up to 30 mum) during the penetration process. Based on Fick's s econd law and assuming a virtually layered structure of the membrane, depth -dependent diffusion coefficients were derived by numerical fitting of the spectroscopic data. For 1-cyanodecane, the diffusion coefficient in the inn er region of the SC is 1.6-fold that measured in the outer region. (C) 2001 Elsevier Science B.V. All rights reserved.