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.