Reducing the thrombogenicity of ion-selective electrode membranes through the use of a silicone-modified segmented polyurethane

The susceptibility of segmented polyurethanes (SPUs) to in vivo oxidative c leavage and hydrolysis constitutes a drawback in the use of these materials in the fabrication of implantable devices. The introduction of poly(dimeth ylsiloxane) (PDMS) groups into the polymer main chain has been previously r eported to enhance the stability of SPUs. Herein, we evaluated the use of B ioSpan-S, a silicone-modified SPU, in the design of membranes for cation-se lective electrodes. The resulting electrodes exhibited good potentiometric response with all of the tested ionophores (valinomycin, sodium ionophore X , and nonactin). The obtained selectivity coefficients meet the selectivity requirements for the determination of sodium and potassium in blood. Moreo ver, as reflected by SEM studies, membranes prepared with BioSpan-S showed less adhesion of platelets than membranes prepared with conventional poly(v inyl chloride) (PVC). These results lead to the conclusion that BioSpan-S w ould be an appropriate candidate for the fabrication of implantable ion-sel ective electrodes.