Piezoelectric Performance of Microcellular Polypropylene Foams Fabricated Using Foam Injection Molding as a Potential Scaffold for Bone Tissue Engineering

Piezoelectric properties and adequate porosity play important roles in bone tissue engineering. In this paper we describe the fabrication of piezoelectric polypropylene (PP) foam using injection molding to be utilized as a potential cost-effective scaffold for bone tissue engineering. One-side mechanical skin removal from the foam was used to investigate the effect of the solid skin on the piezoelectric performance. The microcellular structure, relative density, crystalline structure, mechanical properties, piezoelectric properties under repeated impact pressure and biocompatibility of the scaffolds were investigated using scanning electron microscopy (SEM), water displacement method, differential scanning calorimetry (DSC), uniaxial tension tests, piezoelectric tests and MTT assays, respectively. Uniform spherical cells, with an average size of 75 mu m and a density of 1.23 x 10(6) cells/cm(-3), suitable for bone regeneration, were imaged by SEM. The DSC results showed beta crystals formation in the PP foam during the foaming process which would be valuable for mechanical properties. The foaming process did not reduce the mechanical properties significantly. The foaming process promoted the piezoelectric responses by 134, 922, and 87%, respectively, for the PP samples with 3, 2 and 1 mm thickness. The biocompatibility test suggested improved cellular biocompatibility by foaming. Overall, the results demonstrated the development of a cost-effective scaffold for tissue engineering.