Ferapontova, E. E.; Olsen, E. M.; Gothelf, K. V.
J. Am. Chem. Soc. 2008, 130, 4256–4258, doi: 10.1021/ja711326b
Danish National Research Foundation: Centre for DNA Nanotechnology (CDNA), Department of Chemistry and iNANO, The Faculty of Science, Aarhus University, Langelandsgade 140, DK-8000 Aarhus C
An electrochemical RNA aptamer-based biosensor for rapid and label-free detection of the bronchodilator theophylline was developed. The 5′-disulfide-functionalized end of the RNA aptamer sequence was immobilized on a gold electrode, and the 3′-amino-functionalized end was conjugated with a ferrocene (Fc) redox probe. Upon binding of theophylline the aptamer switches conformation from an open unfolded state to a closed hairpin-type conformation, resulting in the increased electron-transfer efficiency between Fc and the electrode. The electrochemical response, which was measured by differential pulse voltammetry, reaches saturation within a few minutes after addition of theophylline, and the dynamic range for detecting theophylline is 0.2-10 muM. The electrode displays an inhibited response when applied directly in serum samples treated with RNase inhibitors; however a full response to the theophylline serum concentration was obtained by transferring the electrode to blank serum-free buffer solutions. It was demonstrated that theophylline is detected with high selectivity in the presence of caffeine and theobromine.