Comparison of ATR-FTIR spectra of porcine vaginal and buccal mucosa with ear skin and penetration analysis of drug and vehicle components into pig ear.

In the present study, porcine buccal and vaginal mucosae were successfully characterised by ATR-FTIR for the first time and compared to porcine ear skin. By analysing typical bands of the spectra, the structure of proteins and the lipid matrix were elucidated. According to the body site, differences in membrane permeability were detected when analysing the CH2-stretching and -scissoring vibrations. The results indicated a higher permeability for porcine vaginal and buccal tissue compared to skin. Furthermore, the influence of a lecithin-based microemulsion on the barrier properties of the above mentioned tissues was investigated by ATR-FTIR; the results revealed structural changes in all tissues. In addition, the ATR-FTIR technique was employed to semi-quantitatively analyse compounds directly on skin. To this end, tape stripping experiments were performed with a deuterated liposomal drug delivery system containing the model drug flufenamic acid. While the amount of penetrated deuterated liposomes was determined directly on skin samples by ATR-FTIR, the drug amount was analysed by HPLC after extraction of the tape strips since higher sensitivity was achieved in this fashion. Thus, it was possible to monitor the skin penetration of drug and vehicle simultaneously. Interestingly, the results indicated an independent drug penetration after release from the liposomal carrier system.