Current controlled polymeric ion sensors for bioanalysis

Yida Xu, Purdue University

Abstract

Ion-selective electrodes operated under zero-current potentiometry have been developed for many years and have become a routine method for clinical analysis because they are relatively simple to setup, convenient and cost effective to maintain and perform measurements. However, there are still several limitations. The response sensitivity in ion-selective electrodes is limited by the Nernst equation, which gives very small slope for polyionic analytes. The accuracy is dependent on electrode calibration and the stability of the potential at the reference electrodes, which may also be affected by the temperature. The potential readout relies on the ion distribution at the adjacent aqueous/membrane phases, which makes the traditional ion-selective electrodes insensitive to molecular adsorption processes. In this dissertation, two new classes of ion sensors under non-equilibrium control are applied to expand the application of potentiometric ion-selective electrodes. One is pulsed galvanostatic chronopotentiometry, which is initially applied to the detection of protease activity by employing a polyion cleavage reaction. This is further developed for the monitoring of surface adsorption events such as polyelectrolyte multilayers, and taken as a basis for an ion channel mimetic bioaffinity sensor; The other technique is termed backside calibration chronopotentiometry, where the sample ion concentration is found by a critical external current that compensates for the ion concentration gradient across the ion-selective membrane.

Degree

Ph.D.

Advisors

Bakker, Purdue University.

Subject Area

Analytical chemistry

COinS