Optimization of the Electrochemical RNA‐Aptamer Based Biosensor for Theophylline by Using a Methylene Blue Redox Label

Abstract

AbstractThe electrochemical biosensor for theophylline detection in serum based on the RNA molecular beacon approach and methylene blue (MB) as a redox label has been developed. The RNA aptamer for theophylline was immobilized at gold electrodes in its open unfolded state through the alkanethiol linker at its 5′ end, and the MB redox label was attached to the 3′ end of the aptamer. Conformational folding of the aptamer upon theophylline binding increased the electrochemical response from the MB redox probe, then placed closer to the electrode surface. The signal was calibrated versus theophylline concentration within the 2 to 100 μM range, which allows practical determinations of theophylline within therapeutically important 20–100 μM range. The performance of the RNA‐aptamer based biosensor was not inhibited in serum, which was consistent with the absence of detrimental effects of adsorption of serum proteins within the operational potential window of the MB‐labeled biosensor.