Preparation of Electrochemical Aptamer-based Sensors: A direct Aryl Diazonium grafting approach

Abstract

Electrochemical aptamer-based (EAB) sensors represent a promising platform for continuous monitoring of a wide range of biomarkers due to the unique properties of aptamers such as high affinity, target binding reversibility and ease of designing them for a desired target analyte. Currently, the performance of EAB sensors is limited by the instability of the molecule/electrode link that is mostly based on the gold–sulphur semi-covalent bonds that can be chemically and electrochemically unstable during operation of an EAB sensor. In this work, we introduce an aryl diazonium salt derived covalent surface chemistry that enables the direct grafting of aptamers on gold electrodes in a single step by the spontaneous reduction of in situ diazotized aryl-aminated aptamer derivative. This method allows for more robust attachment of aptamers on gold electrodes via the formation of a more stable interfacial gold–carbon bond. The fabricated sensor shows a capability to continuously monitor the antibiotic vancomycin target in phosphate-buffered saline (PBS) solution for over 48 hours. This work opens new venues to overcome the instability related to the thiol–gold chemistry for the development of EAB sensors in wearable devices.