Ion Channel Mimetic Chronopotentiometric Polymeric Membrane Ion Sensor for Surface-Confined Protein Detection

Abstract

The operation of ion channel sensors is mimicked with functionalized polymeric membrane electrodes, using a surface confined affinity reaction to impede the electrochemically imposed ion transfer kinetics of a marker ion. A membrane surface biotinylated by covalent attachment to the polymeric backbone is used here to bind to the protein avidin as a model system. The results indicate that the protein accumulates on the ion-selective membrane surface, partially blocking the current induced ion transfer across the membrane/aqueous sample interface, and subsequently decreases the potential jump in the so-called super-Nernstian step that is characteristic of a surface depletion of the marker ion. The findings suggest that such a potential drop could be utilized to measure the concentration of protein in the sample. Because the sensitivity of protein sensing is dependent on the effective blocking of the active surface area, it can be improved with a hydrophilic nanopore membrane applied on top of the biotinylated ion-selective membrane surface. Based on cyclic voltammetry characterization, the nanoporous membrane electrodes can indeed be understood as a recessed nanoelectrode array. The results show that the measuring range for protein sensing on nanopore electrodes is shifted to lower concentrations by more than one order of magnitude, which is explained with the reduction of surface area by the nanopore membrane and the related more effective hemispherical diffusion pattern.

A Label-Free Potentiometric Sensor Principle for the Detection of Antibody–Antigen Interactions

“…Most electrochemical measurement systems require the addition of an indicator ion to the sample solution (e.g., Ca 2+ ) 18 or a redox couple (e.g., amperometry) to recognize the antibody−antigen interaction. In this sensor principle, the marker ion is delivered by the membrane in direction of the analyte solution by diffusion through the membrane.…”

Non-Fluorescence label protein sensing with track-etched nanopore decorated by avidin/biotin system

“…Multistep functionalization using proteins have been performed with multipore membranes in order to detect, T4 Polynucleotide Kinase [29] or glucose [30] as well as to evaluate enzymatic reaction under confinement [31]. Beside these two detection methods for sensor applications, chronopotentiometry [32] and impedance [33] have also been reported.…”

Advancing Membrane Electrodes and Optical Ion Sensors

“…This insight was further exploited for the establishment of an affinity biosensor approach, using biotin groups covalently attached onto an ionselective membrane. [46] Depending on the sample concentration of avidin, the chronopotentiometric ion response changed, suggesting that surface bound avidin exhibited a similar inhibition of ion transfer as the polyelectrolyte multilayers in the earlier study. This affinity biosensor platform is especially attractive since it avoids metal electrodes and uses non-polar membranes as substrates that may chemically mimic the lipid bilayers present in biological systems.…”