Skin surface model material as a substrate for adhesion-to-skin testing

A model material simulating the mechanical and surface properties of a real human skin was developed for use as a substrate in adhesion-to-skin evaluation. It is a protein–lipid composition possessing film-forming ability. The composition is based on gelatin plasticized by glycerol, polysaccharides and a mixture of lipids that mimick the skin's lipid structure and creates a hydrophobic surface. To enhance the material hydrolytic stability, the composition was cross-linked by formaldehyde, producing a water-swellable but insoluble matrix. The surface topography of a real skin was achieved by a silicone replica technique. Thin films with thickness of 100 ± 10 μm were cast. The effect of the components ratio and preparation technique on the film mechanical, surface and hydrolytic properties was studied. Based on the results obtained, a formulation having mechanical and surface properties comparable to that of a human skin was selected. The relevance of the model material was evaluated in lap-shear and 180°-peel adhesion tests and the results were compared to a finger or a forearm skin of ten healthy volunteers (in vivo tests). For validation purposes, commercial surgical tapes Micropore™ and Transpore™ and Mylar® polyester film were also used. The effects of substrate, adhesive, conditions of the joint preparation and the test employed on adhesion strength were studied. The results obtained show that the mechanical and surface properties of the model material are close to those of the human skin.