Novel poly(urethane-aminoamides): an in vitro study of the interaction with heparin

In order to obtain heparin-binding polyurethanes, tertiary amino-groups hav e been introduced in the polymer backbone by attributing a key-role to the chain extender, i.e. substituting butane diol, commonly used in polyurethan e synthesis, with a tailor-made diamino-diamide-diol. In this work a poly(e ther-urethane-aminoamide) (PEU/PIME/al) was obtained with poly(oxytetrameth ylene) glycol 2000, 1,6-hexamethylene-diisocyanate and the new chain extend er, in the molar ratio 1 :2: 1. The heparin binding capacity of PEU/PIME/al was evaluated with I-125 labelled heparin, using for comparison the analog ous polymer obtained with a diamide-diol (i.e. the poly(ether-urethane-amid e) PEU/PIBLO/al), and two commercially available biomedical polyurethanes ( Pellethane 2363 and Corethane). pH and ionic strength dependence of the hep arin uptake were investigated by treating all the polyurethanes with soluti ons of I-125 heparin into buffers from pH 4 to 9 or NaCl molarity from 0.0 to 1.0. The stability of the interaction with bound heparin was investigate d by sequential washing treatments (PBS, 1 N NaOH, 2% SDS solution), then a nalysing the residual radioactivity on the materials. Results indicated that the heparin binding of PEU/PIME/al is significantly higher and more stable than that of the other polyurethanes, with a time-de pendent kinetic. The interaction with heparin appears to bi prevalently ion ic, with the contribution of other electrostatic and hydrophobic interactio ns. Activated partial thromboplastin time (APTT), performed on human plasma with polyurethane-coated, heparinized test tubes, indicated that bound hep arin maintains its biological activity after the adsorption.