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, for the first time, 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 an