Flash chronopotentiometric sensing of the polyions protamine and heparin at ion-selective membranes

Abstract

We report here on a highly sensitive and rapid detection technique, multipulse flash chronopotentiometry, for the anticoagulant polyion heparin and its antidote protamine. The technique is based on a localized titration of the polyions at the surface of an appropriately formulated polymeric ion-selective membrane devoid of ion exchange properties to prohibit spontaneous extraction processes. A defined ion flux from the sample side to the membrane is induced electrochemically by applying a current pulse of appropriate amplitude and sign. The resulting depletion of the measured ions at the membrane surface gives rise to a characteristic limiting current or transition time and is observed as an inflection point in the resulting chronopotentiogram. The limiting current and the square root of the transition time are linear functions of the concentration of the polyion and yield sensitive and rapid analytical information attractive for clinical diagnostics applications. The polyion protamine is detected in 10-fold diluted blood samples in a matter of seconds via a cathodic current pulse. The utility of the technique for monitoring heparin/protamine titrations in physiological saline solutions is demonstrated.

Detection of protease activities by flash chronopotentiometry using a reversible polycation-sensitive polymeric membrane electrode

“…We report here a novel transduction protocol, called flash chronopotentiometry (FCP) [45–47], as a more rapid, sensitive and direct sensor of protease activities and their inhibitors. It will be shown that sensitive and rapid detection of trypsin and chymotrypsin activities, as well as soybean trypsin inhibitor can be achieved with the new FCP detection scheme using a polycation-sensitive polymer membrane electrode formulated with tridodecylmethylammonium-dinonylnaphthalenesulfonate (TDMA-DNNS), where DNNS serves as a polycationic peptide recognition element.…”

Advancing Membrane Electrodes and Optical Ion Sensors

“…This approach was successfully established for membrane electrodes selective for hydrogen ions, [47] calcium [48] and the polyion protamine, [49] and gave critical times on the order of 1-2 s for concentrations up to ca. 1 mM.…”

Dynamic electrochemistry with ionophore based ion-selective membranes

“…Subsequently, Bakker and Meyerhoff explored localized ion depletion of protamine and heparin in separate work. 56,58 Even though the results were signicant, the selectivity of the membranes were not sufficient to detect these important drugs in undiluted whole human blood.…”

“…Furthermore, localized ion-depletion was not only used for detecting small hydrophilic ions but also for polyions such as protamine/heparin and enzymes. 55,56 Meyerhoff has pioneered the detection of such polyions employing potentiometric polymeric membranes. 57 However, the spontaneous extraction of these charged molecules into the membrane phase complicate the potentiometric measurements because they give rise to continuous signal dri and irreversible responses.…”