Synthesis and characterization of redox-sensitive polyurethanes based on L-glutathione oxidized and poly(ether ester) triblock copolymers

Segmented polyurethanes, based on PCL-PEG-PCL copolymers, 1,4-diisocyanatobutane and L-glutathione oxidized, used as chain extender, were synthetized. Three different reactions conditions were investigated using three different copolymers having ɛ-CL/polyethylene glycol molar ratios equal to 12, 24 and 36 and three different reaction conditions. As investigated by size exclusion chromatography analyses and quantification of L-glutathione, the polymerization and the extension phase's efficiency depended on the ɛ-CL/PEG ratio and the extension phase's operating temperature. Three selected polyurethanes were characterized by spectroscopic, differential scanning calorimetry (DSC) and X-ray diffraction (XRD) analyses. Polyurethanes processed as films showed a hydrolysis pattern dependent on the crystallinity of their soft segments, which was not influenced by the incubation in a reductive mimicking environment. Instead, a redox-sensitive release of methotrexate, used as a model drug, was demonstrated.