A BDD-Au/SPCE-based electrochemical DNA aptasensor for selective and sensitive detection of theophylline

The proposed aptasensor using a DNA aptamer for the detection of theophylline (THEO) is being reported for the first time, as previous methods predominantly employed RNA aptamers. DNA aptamers have attracted significant attention due to their advantages over antibodies, including greater stability and cost-effectiveness, making them ideal for various diagnostic applications as biosensors. THEO, a drug commonly used in the treatment of respiratory diseases such as asthma, requires precise monitoring in the bloodstream due to its narrow therapeutic index. In this paper, we present the first optimization of THEO detection using a DNA aptamer-based sensor (aptasensor), utilizing a composite boron-doped diamond/Gold (BDD-Au) on screen-printed carbon electrodes. Thiolated DNA aptamers were immobilized on the BDD-Au surface, where they selectively targeted THEO in biological samples. Optimization of the aptasensor was achieved using a Box-Behnken design, determining optimal conditions of 3.0 μM for aptamer concentration, 90 min for aptamer immobilization time, and 1.0 mM for tris(2-carboxyethyl)phosphine concentration. The resulting DNA aptasensor demonstrated excellent selectivity for THEO, with a linear detection range from 1 to 1.0 mM and a detection limit of 52 nM. The sensor maintained stability for up to four weeks and exhibited high recovery rates when tested in blood serum, highlighting its potential for clinical monitoring of THEO levels.