Effect of surface-attached heparin on the response of potassium-selective electrodes.

Heparin (or hydrolyzed heparin) was covalently attached on the surface of derivatized cellulose triacetate membranes, which were subsequently impregnated with the potassium-selective ionophore valinomycin. The resulting ion-selective electrodes presented near-Nernstian response to potassium and had selectivity coefficients of the same order of magnitude as those of conventional poly(vinyl chloride)-based electrodes. It was found that the heparin layer does not alter significantly the response characteristics of the electrodes. The biological activity of the immobilized heparin (or hydrolyzed heparin) was measured in terms of its inactivation of blood coagulation factor Xa. It was found that the covalently anchored hydrolyzed heparin was not biologically active, but the immobilized heparin was able to inactivate factor Xa. Therefore, by covalently attaching heparin on the surface of ion-selective electrodes, electrodes with improved blood compatibility characteristics may be prepared.