PDMS-based polyurethanes with MPEG grafts: Mechanical properties, bacterial repellency, and release behavior of rifampicin

PDMS-based polyurethanes (PUs) grafted with monomethoxy poly(ethylene glyco l) (MPEG) were synthesized to develop a coating material for urinary cathet ers with a silicone surface for minimizing urinary tract infections. MPEG w as grafted on PDMS-based PUs by two methods depending on the PU synthetic r outes: esterification and allophanate reactions. It was confirmed from mech anical characterization that an increase of the hard segment amount enhance d the ultimate strength and Young's modulus. while reducing elongation at t he end-points. The incorporation of MPEG in PDMS-based PUs induced a decrea se in tensile strength and Young's modulus, and increased elongation at the break point due to its high flexibility. When hydrated in distilled water, mechanical properties of all PUs synthesized in this study deteriorated du e to water absorption. It was evident from the bacterial adhesion test that PDMS-based PUs showed moderate resistance to adhesion of E. coli on their surfaces compared to Pellethane(R). while the incorporation of MPEG signifi cantly enhanced repellency to bacteria, including E. coli and S. epidermidi s. We also studied the release behavior of an antibiotic drug, rifampicin, from the polymeric devices fabricated by solvent evaporation. Although rifa mpicin is hydrophilic and soluble in pH 7.4 phosphate buffer, it showed a s ustained release over 45 days from PDMS-based PUs with MPEG that were graft ed on ethylene glycol residues by allophanate reaction. This release charac teristic was predominantly influenced by a hydrogen bond interaction betwee n the polymers and rifampicin, which was confirmed through an ATR-IR study. This may imply that the specific interaction is responsible for the delaye d release. Considering the mechanical properties, morphologies of drug-inco rporated polymeric matrices, and drug release behaviors, PDMS-based PU with MPEG that were grafted on ethylene glycol (a chain extender) residues by a llophanate reaction showed better material properties for uretharal cathete r coating pusposes in order to minimize urinary tract infections.