Poly(alkylene sebacate ether)urethane hydrogels for indomethacin delivery formulations

A series of aliphatic polyurethane hydrogels based on poly(alkylene sebacate) diols was developed by polyaddition reaction. The chemical structures of unloaded and indomethacin-loaded poly(alkylene sebacate ether)urethane hydrogels were characterized using ATR-FT-IR spectroscopy. The aim of this research was to study the influence of the long alkylene chains on the indomethacin release rate. The swelling kinetics was analyzed using power law and second-order equation and it was found that both diffusion and polymer relaxation mechanisms control the overall rate of water uptake. The release mechanism follows the same behavior as swelling, but the interaction of the drug with the hydrophobic matrix influences the release kinetics. The surface properties and the influence of the surface configuration on the indomethacin release kinetics were also investigated using contact angle measurements. The mechanical properties of the dry samples were affected by the crosslinker, while, for the swollen samples, the stress–strain curves were overlapping and the mechanical parameter values decrease. The swelling of these hydrogels was also attributed to the network porosity, which was revealed by scanning electron microscopy (SEM) on freeze-dried specimens. The results prove the importance of the polyurethane matrix structure in the development of new drug releasing systems.