Uncovering Adenosine‐Specific Signals: A Label‐Free Aptamer‐Based Approach with Gold Nanoparticles for Specific Detection

Abstract We present a novel colorimetric aptasensing method for specific adenosine (Ade) detection based on complementary aptamer hybridization and gold nanoparticles (AuNPs). Unlike traditional approaches, our method overcomes limitations of selectivity and specificity by incorporating an additional step involving the complementary strand of the aptamer (c‐Ade aptamer) after incubating Ade with the aptamer. In the absence of Ade, the c‐Ade aptamer hybridizes with the aptamer, causing AuNPs aggregation and a blue color change. However, in the presence of Ade, the aptamer‐bound target prevents hybridization, allowing the free c‐Ade aptamer to adsorb onto the AuNPs, resulting in a red color change. This unique color reversal distinguishes our approach from conventional label‐free methods. We optimized the detection conditions, including incubation time and salt concentration, to enhance sensitivity and reproducibility. The calibration curve exhibited a linear relationship between the colorimetric response and Ade concentration, with a limit of detection of 3.0±0.8 nM. Our method demonstrated excellent selectivity for Ade, even in the presence of structurally similar interfering compounds. Furthermore, we successfully applied our approach to detect Ade in complex biological samples with minimal sample preparation. Our colorimetric aptasensing method offers a simple, cost‐effective, and specific tool for detecting targets in various applications.