New polyurethane compositions containing high amounts of covalently bonded heparin

Heparin was bonded covalently to hydrophilic polyurethanes. Polymers were characterized by spectroscopic techniques (IR and H-1, C-13 NMR), molecular weight measurements and differential scanning calorimetry. The heparin content of the polymer films (up to more than 500 mu/cm2) was determined by a calorimetric system, and its biological activity was evaluated in vitro by APTT (activated partial thromboplastin time) measurements with a tenfold increase of the clotting time (about 300 s) with respect to the clotting time of human plasma (30 s). When heparin is bonded to a polymer provided with a hydrophilic polyfunctional spacer, the heparin content of the films is remarkably higher than previously described (about twice the reported values), and also the biological activity of the bonded heparin is favourably affected.