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 epsilon-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 Lglutathione, the polymerization and the extension phase's efficiency depended on the epsilon-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.