Polyurethanes with separately tunable biodegradation behavior and mechanical properties for tissue engineering

Two series (random and block) poly(glycolide-co-epsilon-caprolactone) macrodiols with various glycolide to epsilon-caprolactone ratios (50/50 and 30/70, R-PG50C, R-PG30C, B-PG50C, and B-PG30C) were synthesized. Next, segmented polyurethanes (PUs) were synthesized based on the synthesized macrodiols, 1,6-hexamethylene diisocyanate and 1,4-butanediol (PU-R30, PU-R50, PU-B30, and PU-B50). Effect of glycolide (G) and epsilon-caprolactone (C) monomers arrangement (random or block) on the PUs properties were investigated via FTIR, H-1 NMR, DSC, TGA, DMA, SEM, and mechanical tests. All PUs illustrated T-g (-33 degrees C to -48 degrees C) and T-m (102 degrees C to 139 degrees C) corresponding to the soft and the hard segments, respectively. Polymers based on block macrodiols also showed T-m related to the soft segments. While PUs underwent a two-step thermal degradation, the PUs based on block macrodiols indicated higher degradation temperature. Dynamic mechanical analysis results evidenced development of a well-defined microphase separated structure in PU-R30. Contact angle (about 70 degrees-80 degrees) and water uptake (around 20% after 24hours) of the PU films are close to those suitable for tissue engineering materials. The PU based on R-PG30C (PU-R30) exhibited the highest tensile strength (2.87MPa) followed by PU-B50 and PU-R50. Over a 63-day in vitro degradation study in phosphate buffered saline, the PUs showed variable weight loss (up to 40%) depending on their soft segments composition and arrangement. Also, the PUs showed no cytotoxicity. Thus, these PUs with tunable biodegradation rate and mechanical properties are suitable candidates for tissue engineering.