Study of the tensile properties of living skin equivalents.

The living skin equivalent is one of the more advanced clinical applications in the field of tissue engineering. It is a promising therapeutic option for burn victims and a strong potential for manifold in vitro experiments. However, researchers have encountered major drawbacks in the reconstruction of the dermal layer. Peripheral anchorage of the dermal equivalent component has been a valuable solution to many of these problems. In this work, we have carried out the mechanical analysis of skin equivalent models, based on this dermal anchoring technique, with a study of their biaxial tensile properties. Differences between models were related to the origin of collagen, either bovine or human, and on the culture techniques: immersion or at the air-liquid interface. The study was accomplished in vitro using 25.4-mm-diameter disk-shaped specimens with an indentation test. In appropriate wet condition, the specimens were punctured with a spherical tip at a quasi-static rate. We measured the load applied against the tip vs deflection up to the breaking point. Our results show that skin equivalents presented a typical exponential load-deflection relationship. All skin equivalents presented large extensibility up to 1.41 expressed in a ratio of deflection vs specimen's radius. The maximum tensile strength (0.871-1.169 Newton) and energy calculations (3.75-6.432 N.mm) was offered by living skin equivalent, made with human types I and III collagens, cultured at the air-liquid interface. In these conditions, our results suggest the tensile properties of living skin equivalents were enhanced due to the development of well stratified stratum corneum.