Design, synthesis and properties of polyurethane hydrogels for tissue engineering

Due to their similarity to natural soft tissues, water-swellable polymeric materials (hydrogels) are, in principle, ideal candidates for scaffolds/matrices in tissue engineering. Polyurethanes (PU), hydrophilic but water-insoluble, can be obtained by the incorporation of hydrophilic soft segments, e.g. poly(ethylene oxide) (PEO). These materials possess the favorable characteristics of the family of PUs as well as the ability to mimic soft tissues. In this work, new crosslinked PU-hydrogels were prepared in a one-step bulk polymerization process using an aliphatic diisocyanate, PEO, a low molecular weight diol, and a tri-functional crosslinking agent. A porous structure was also obtained by air-incorporation under mechanical stirring at a controlled high speed during the polymerization. Structural characteristics of the compact (PU-HyC) and the porous (PU-HyP) material were investigated. Molecular weight between cross-links, M(c), and crosslinking density, rho(x), were typical of a low crosslinking degree. A homogeneous distribution of non-interconnecting pores (phi100 microm) was observed in PU-HyP. Both materials showed a high water adsorption. The swelling behavior and weight loss in water was affected by porosity. For their mechanical behavior in the swollen state, the novel PU hydrogels can be considered for biomedical applications where good mechanical properties are required (i.e. 3D scaffold for tissue engineering).