Polyurethane-Grafted Chitosan as New Biomaterials\nfor Controlled Drug Delivery

Abstract

The\npresent investigation focuses on the grafting of chitosan (CHT)\nwith diisocyanate terminated polyurethane. Solid state ¹³C NMR spectroscopy confirms the grafting reaction and the degree\nof substitution (DS) was calculated from the deconvoluted area of\nthe corresponding NMR peak. Solubility studies, swelling behavior\nand contact angle measurements support the hydrophobic chemical modification\non CHT molecules and higher DS leads to the cross-linking of CHT molecules\nhaving polyurethane bridges resulting insolubility and regulated swelling\nin the graft copolymer. Molecular relaxations phenomena due to the\nconstraint associated with the grafting have been revealed using spin–lattice\nrelaxation tine (<i>T</i>₁) and shifting of peak\nposition in tan δ curve toward lower temperature in dynamic\nmechanical measurement at constant frequency indicating flexible nature\nof graft copolymers as compared to pure CHT. The sustained drug delivery\nhas been achieved using graft copolymers vis-à-vis pure CHT\nfollowing the Fickian diffusion behavior (<i>n</i> ≤\n0.45) and the release rate can be tuned by altering the DS. In depth\nbiocompatibility studies through platelet aggregation, platelet adhesion,\nreactive oxygen species of the developed graft copolymers, and <i>in vitro</i> hemolysis assay and cell viability have been performed\nto understand its potential use in biomedical applications and compared\nthe improved properties with respect to pure CHT. Hence, bio- and\nhemocompatible CHT graft copolymers have been developed with the capability\nof controlled and sustained drug release.