Biocompatible thermo- and magneto-responsive shape-memory polyurethane bionanocomposites.

Thermo- and magneto-responsive shape-memory bionanocomposites based on a bio-based polyurethane and magnetite nanoparticles were prepared. Due to the structure of the reactants, the behavior of the polyurethane matrix differs from common polyurethanes, since the soft segment was formed by a diisocyanate and a chain extender, whereas the macrodiol served as hard segment. The influence of the magnetite nanoparticles on the thermal and mechanical properties and the shape-memory behavior was studied. It was observed that magnetite nanoparticles interacted with macrodiol-rich domains and decreased the overall crystallinity of the material, although their presence did not affect the mechanical properties to a great extent. At the same time, the magnetite nanoparticles increased the shape fixity and contributed to shape recovery. The bionanocomposites exhibited magnetic behavior and could be easily heated in an alternating magnetic field, allowing fast and almost complete shape recovery. Preliminary cytotoxicity, hemocompatibility, and cell adhesion analysis suggest that the new materials are benign and potentially useful for biomedical applications.