Improving the blood compatibility of polymeric membrane ion-selective electrodes.

Abstract

Efforts to monitor blood gases and electrolytes through miniaturization of polymer membrane-type sensors into catheter forms have been hampered by the challenge of fabricating devices that exhibit acceptable blood compatibility. In this work, in vitro platelet adhesion studies are conducted to compare the thrombogenic properties of various polymer matrices useful for preparing implantable ion-selective membrane electrodes (ISEs). Conventional plasticized poly(vinyl chloride) and alternate polyurethane materials doped with proton and potassium selective ionophores are shown to be potentially thrombogenic. New methods are investigated that improve the biocompatibility of these sensing membranes without causing a concomitant degradation in their analytical response properties. One approach investigated shows that a marked decrease in platelet adhesion is observed when polyurethane (Tecoflex)-based membranes are coated with a thin photocrosslinked layer of poly(ethylene oxide). Such surface-modified membranes are shown to retain potentiometric ion response properties essentially equivalent to untreated membranes. A second approach examined to improve blood compatibility is the incorporation into the sensing membranes of compounds capable of releasing the antiplatelet agent nitric oxide (NO). It is found that the potentiometric response properties, NO release characteristics and corresponding antiplatelet effects of the polymeric membranes containing a zwitterionic diamine/NO adduct compound (N,N\sp\prime-dimethylhexanediamine nitric oxide adduct) make them potentially useful for fabricating non-thrombogenic electrochemical sensors. This work also includes a study regarding the influence that poly(ethylene oxide)-based nonionic surfactants (of the type commonly present in calibration and wash solutions used in the operation of many commercial blood gas/electrolyte analyzers and water quality instruments) may have on the potentiometric response properties of hydrogen-ion selective polymeric membrane ISEs. The effects induced by partitioning of such surfactants into the electrode membranes are described and an appropriate model is developed to explain the observed loss in selectivity over other cations \rm (Na\sp+,\ K\sp+) when polymeric pH electrodes are operated in solutions containing such surfactants.Ph.D.Analytical chemistryApplied SciencesBiomedical engineeringPure SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/129983/2/9711960.pd