Regenerated keratin films : an alternative to human skin in in vitro drug permeability studies

Purpose This work aimed to develop a film made of regenerated keratin (RK) suitable as an alternative to human skin in in vitro drug permeability studies. Materials and methods The films were obtained by casting the RK solution obtained by extracting keratin from sheep’s wool by sulphitolysis. The investigated variables were the presence of two types of ceramide, namely CER III and CER IV, and film thickness. The surface morphology of and structural integrity of films was examined by SEM. The molecular conformation of RK was studies by FTIR spectroscopy. The permeation of ibuprofen (IB), selected as model drug, through the films or human epidermis was determined by using Franz diffusion cells. Results The films presented a smooth and homogenous surface. The thickness of films was ranging from 140 μm to 180 μm. ATR-FTIR spectroscopy revealed that RK in cast film was organized in the β-sheet conformation. The addition of 1% w/w CER III and CER VI to RK film (140 μm thickness) significantly reduced the IB flux (RK film: J=9±0 μg x h/cm2; CER RK film: J=6±2 μg x h/cm2). The increase of thickness to 180 μm in CER RK film further decreased the IB flux (CER RK film: J=2±0 μg x h/cm2). Both fluxes resulted close to those of human epidermis from three different donors (J1= 6±1 μg x h/cm2; J2= 3±0 μg x h/cm2; J3= 2±0 μg x h/cm2). Conclusion RK appears promising a material to develop membranes suitable for preliminary screenings in in vitro permeability studies.