Web Release Date: January 10,
Aptamer-Based Potentiometric Measurements of Proteins Using Ion-Selective Microelectrodes
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Department of Chemistry, Purdue University, West Lafayette, Indiana 47907, The Biodesign Institute and Fulton School of Engineering, Arizona State University, Tempe, Arizona 85287, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla, 90112, Thailand, Laboratorium für Organische Chemie, ETH Zürich, CH-8093 Zürich, Switzerland, and Nanochemistry Research Institute, Department of Applied Chemistry, Curtin University of Technology, Perth, WA 6845, Australia
Received for review September 12, 2007. Accepted October 27, 2007.
Abstract:
We here report on the first example of an aptamer-based
potentiometric sandwich assay of proteins. The measurements are based on CdS quantum dot labels of the
secondary aptamer, which were determined with a novel
solid-contact Cd2+-selective polymer membrane electrode
after dissolution with hydrogen peroxide. The electrode
exhibited cadmium ion detection limits of 100 pM in 100
mL samples and of 1 nM in 200 
L microwells, using a
calcium-selective electrode as a pseudoreference electrode. As a prototype example, thrombin was measured
in 200 L samples with a lower detection limit of 0.14
nM corresponding to 28 fmol of analyte. The results show
great promise for the potentiometric determination of
proteins at very low concentrations in microliter samples.
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