pH-Responsive and degradable polyurethane film with good tensile properties for drug delivery in vitro

In this paper, we synthesized a new type of pH-responsive block polyurethane (PMCU) through the condensation polymerization of N-methyldiethanolamine (MDEA), poly(epsilon-caprolactone) and 4,4'-dicyclohexylmethane diisocyanate. The chemical structure of the PMCU were characterized, and the influence of MDEA content on the physicochemical properties of the casted PMCU films were studied detailly. The tensile test demonstrated the good tensile properties of the PMCU films with the breaking strain of 983-425% and the ultimate strength of 11.7-31.2 MPa. The tertiary amine groups and polyester segments endowed the material with pH sensitivity and hydrolytic degradability, respectively. The pH responsiveness of the films was confirmed from the enhanced equilibrium swelling ratio (ESR) with decreasing pH value of the medium, and the ESR in acidic condition (pH 1.5) was much higher than that in neutral (pH 7.0) and basic (pH 12.0) conditions. The studies of drug sustainedrelease in vitro at different pH indicated a pH-dependent release efficiency, which was closely related with the ESR and almost unaffected by the slow hydrolytic degradation. In addition, the cytotoxicity assay showed that the PMCU had good cytocompatibility to L929 cells. This study showed that pH-responsive promising platform for targeted drug delivery in the biomedical areas.