Polymer membrane sensors for continuous intravascular monitoring of blood pH.

A new type of pH sensor suitable for chronic intra-vascular implantation by virtue of its small size, flexibility, and ruggedness was constructed and evaluated. The pH-sensitive element was a thin film of an elastromeric polymer made ion permselective to proteons by adding a lipophilic, specific H+-ion carrier. This was coated onto small diameter silver wires to form sensors. In preliminary trials in anesthetized dogs, the sensors permitted continuous, accurate in vivo blood pH measurement with rapid response (less than 0.1 s).

The effect of uncouplers of oxidative phosphorylation on lipid bilayer membranes: Carbonylcyanidem-chlorophenylhydrazone.

Detailed experimental data for conductivity and membrane potentials are presented for lecithin/cholesterol/decane bilayers in the presence of the uncoupler carbonylcyanidem-chlorophenylhydrazone (CCCP). These compare favorably with a theoretical model derived to explain the mechanism of action of uncouplers on bilayers. The model assumes that the weak acid uncoupler HA and its anion A(-) are the sole species which permeate the membrane. Its key feature is the recognition of the existence of unstirred aqueous layers on either side of the membrane. The model accounts for, among other things, a maximum in the transmembrane conductivity at a pH to the alkaline side of the uncoupler pK a and saturating current-voltage characteristics at high pH, both phenomena being found for CCCP. From a quantitative fit of model to data, values of 2.0×10(-3) and 11 cm/sec are deduced for the permeability coefficients of the CCCP anion and the undissociated CCCP molecule, respectively.