Polymers and Scaffolds with Improved Blood Compatibility and Enhanced Cellular Response with Focus on Polyurethane Foams Functionalized with Amino-Amide Groups

Biofunctionalization of biomaterial substrates has gained increasing interest in Tissue Engineering (TE) to create functional scaffolds with improved performances and capable of directing cellular behaviour. This work takes into account the functionalization of polyurethane (PU) foams with an active molecule, the diamino-diamide diol PIME, purposely designed to be inserted in the structure of linear PUs and previously found to be able to improve hemo-, cytocompatibility and bacterial resistance of these biomaterials. Here, for the first time, the gas foaming process previously set up for biocompatible PU foams was modified, and different methods were tested to obtain structurally stable foams containing PIME. The obtained foams and respective controls showed appropriate porosity (Ø = 407 ÷ 589 ± 30 μm; > 90% open porosity), similar density (≈ 0.14 g/cm3) and hydrophilicity (water uptake ≈ 300%) and adequate compressive properties (E = 0.058 ÷ 0.170 Mpa; Hysteresis Area = 2.07 ÷ 5.59 x 10-3 J/cm3, < 5% residual deformation). PU foams containing PIME exhibited a more spherical pore geometry; the foam obtained by applying a higher stirring speed during synthesis (PU-3kP) exhibited a lower mean pore size and an elastic modulus higher than that of the other foams. FT-IR spectroscopy indicated the presence of new absorption bands and structural changes attributable to the presence of PIME. Cytotoxicity tests performed with the cell line L929 verified the absence of cytotoxic effects. All foams were able to support L929 fibroblasts proliferation and vitality for seven days; PIME-containing foams showed higher values of cell proliferation (p<0.05) that the respective controls