Conducting Polymer-Based Electrochemical Aptasensor for the Detection of Adenosine

Emerging research in the area of conducting polymer-based electrochemical biosensors has revealed the need for the development of techniques that can enable easy functionalization with biorecognition molecules and enhance biosensor stability. In this work, an electrochemical biosensor for the detection of the small molecule adenosine was developed utilizing a conducting copolymer as a transducing agent. First, a method was developed to modify the surface of indium tin oxide-coated glass slides to enable robust copolymer deposition. A 3,4-ethylenedioxythiophene (EDOT) and 2H-thieno­[3,4-b]­[1,4]­dioxepin-3,3­(4H)-diacetic acid (ProDOT–(COOH)₂) copolymer was then electrochemically grown on the surface of the modified slides. This copolymer was used to covalently attach an aptamer specific to adenosine to the biosensing platform to provide the system with target selectivity. The electroactivity of the conducting polymer before and after aptamer attachment in aqueous electrolyte solutions was studied. The attachment of the aptamers to the conducting polymer was confirmed using fluorescence microscopy and cyclic voltammetry. The fabricated aptamer-based sensors were then used for the electrochemical detection of adenosine, and the performance of the sensor was investigated. The adenosine aptasensor had a limit of detection of 2.33 nM and a linear range from 9.6 nM to 600 μM. The adenosine aptasensor showed good selectivity against competing interfering agents and specificity relative to scrambled oligonucleotide stands. In addition, the sensor showed good stability for up to 6 days when stored in 0.1 M phosphate-buffered saline or argon.