Polymer membrane-based ion-, gas- and bio-selective potentiometric sensors

Recent progress in the design of new polymer membrane-based potentiometric ion-, gas- and bio-selective electrodes in chemistry laboratories at the University of Michigan (Ann Arbor) is reviewed. Emphasis is placed on describing the performance of devices for measuring anions (e.g., salicylate, thiocyanate, chloride and heparin) and gases (e.g., ammonia, carbon dioxide and oxygen) in biological samples, both in vitro and in vivo. Beyond direct measurement of key ions and gases in complex matrices, some of the new membrane electrode systems reported can serve as base transducers for the development of biosensors containing integrated biological reagents, including enzymes and antibodies. New approaches for mass fabricating solid-state ion and biosensor devices as well as future directions for research in the entire field of polymer membrane sensors are also described.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/31010/1/0000685.pd

ortho-Substituent effects on the in vitro and in vivo genotoxicity of benzidine derivatives

Benzidine and its 3,3'-diamino, 3,3'-dimethyl, 3,3'-dimethoxy, 3,3'-difluoro, 3,3'-dichloro, 3,3'-dibromo, 3,3'-dicarbomethoxy and 3,3'-dinitro derivatives together with 2-nitrobenzidine and 3-nitrobenzidine were compared for their in vitro and in vivo genotoxicity. Relative mutagenicity was established with Salmonella strains TA98, TA98/1,8-DNP6 and TA100 with and without S9 activation. All the derivatives in the presence of S9 were more mutagenic than benzidine with 3,3'-dinitro- and 3-nitro-benzidine having the greatest mutagenicity. Mutagenicity in all 3 strains with S9 activation could be correlated to electron-withdrawing ability of substituent groups, as measured by the basicity of the amines. This correlation was explained on the basis that electron-withdrawing groups could favor the stability of the mutagenic intermediate N-hydroxylamine and also enhance the reactivity of the ultimate mutagenic species, the nitrenium ion. Mutagenicity was also correlated to the energy of the lowest unoccupied molecular orbitals (ELUMO). Hydrophobicity was found to have very limited effect on the relative mutagenicity of our benzidine derivatives. The in vivo endpoint was chromosomal aberrations in the bone-marrow cells of mice following intraperitoneal administration of benzidine and its derivatives. In contrast to the in vitro results, while all the amines were genotoxic in vivo, only the 3-nitro derivative had a significant increase in toxicity over benzidine.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/30582/1/0000219.pd

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

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