Double Layer Porous Structures by an Injection Molding/Particulate Leaching Approach

Scaffolds as a temporary substitute for the extracellular matrix should provide interconnected pores and often require a multilayer design to mimic the geometry and biomechanics of the target tissue. Here, it was explored whether bilayer porous structures can be obtained by a process free of organic solvents and how the individual layers contribute to the overall elastic properties. Porous layers were obtained from polyurethane (PU) blends with polyvinyl alcohol (PVA), which were immersed in water after sequential injection molding. Pore sizes in both layers ranged from 1m to 100m with an average of 22 +/- 1m at a porosity of 50 +/- 5% in combination with a high interconnectivity. The pore sizes were tailored by applying an annealing treatment, while the porosity was kept constant. Mechanical properties of the individual layers and the double layer constructs as determined by tensile tests suggested that the overall elasticity of the compact bilayer construct and porous bilayer construct was in agreement with the predicted overall elasticity according to the rule of mixtures. The porous bilayer model system will serve as a basis for determining structure-property relationships with respect to pore size, porosity as well as mechanical properties of individual layers and in this way enable a knowledge-based design of layered scaffolds.