A CRITICAL COMPARISON OF SOME RAMAN-SPECTROSCOPIC TECHNIQUES FOR STUDIES OF HUMAN STRATUM-CORNEUM

This study evaluates a variety of techniques and sampling conditions f or Raman spectroscopic investigations of human stratum corneum. Using a Fourier-transform Raman system and samples of stratum corneum in vit ro, we demonstrated minimal inter- and intracadaver variations in mole cular vibrations. We have also shown Raman spectroscopy to be relative ly insensitive to the hydration state of human stratum corneum, indica ting that the technique should be valuable for monitoring the transder mal delivery of drugs from aqueous solutions. The stability of human s tratum corneum to near-infrared laser excitation was verified by spect ral collection for approximately 1 hr. We have also compared FT-Raman spectra from human stratum corneum in vitro and in vivo. Of the differ ent types of Raman instruments used in this study (visible-light excit ation microprobe, visible-light excitation macroscopic sampling, and F ourier-transform Raman), the FT-Raman system provided good-quality spe ctra with high sample throughput, but systems using visible-light exci tation should provide unique information for use in specialist applica tions.