The highly tunable mechanical properties and resilience of polyurethanes make them promising candidates for tissue engineering applications. Biodegradability is conferred by incorporation of hydrolytically or enzymatically cleavable moieties into the polyurethane structure. A common choice for the biodegradable soft segment is a poly(ether ester) triblock copolymer synthesized by ring opening polymerization of the polyester from a polyether macroinitiator. Herein, we describe a new "plug-and-play" approach for triblock synthesis based on urethane block coupling that enables finer control of block lengths and ease of segmental tuning. The inclusion of urethane linkages in the soft segment was also hypothesized to promote hydrogen bonding between the segments with an associated increase in modulus, tensile strength, and ultimate elongation. Hard segment content of the biodegradable polyurethane urea was varied to demonstrate the tunable tensile properties and degradation rate. As expected, increasing hard segment content led to large increases in initial secant modulus and tensile strength. A corollary decrease in ultimate elongation, elastic recovery, and degradation rate was also observed with increasing hard segment content. Finally, cytocompatibility and hydrolytic degradation of electrospun polyurethane meshes were evaluated to establish the potential use of these biodegradable matrixes as tissue engineering scaffolds. All of the polyurethane formulations displayed comparable cytocompatibilty to tissue culture plastic controls and hydrolytic chain scission of the polyester soft segment. Overall, this synthetic approach provides a platform to produce biodegradable polyurethane ureas with enhanced control over segmental chemistry, mechanical properties, and degradation rate.
Keywords: hydrolytic degradation; polycaprolactone; polyethylene glycol; polyurethane.