“…Currently, cortisol is detected via a spectrophotometric (absorbance or fluorometric) assay, high-performance liquid chromatography (HPLC), liquid chromatography-mass spectroscopy (LC-MS), enzyme-linked immunosorbent assay (ELISA), or surface plasmon resonance (SPR). , These techniques tend to be time-consuming, require skilled personnel, and are instrument-dependent, leaving them laboratory-bound. Recently, electrochemical-based assays have gained popularity due to their low cost, high sensitivity, and high level of integration, especially in portable form factors. − While most electrochemical techniques use an assay similar to ELISAs, a new format using affinity reagents with conformation-changing properties is appealing since the electroactive reporter can be directly conjugated to the probe molecule, removing the need for a second recognition element. − Aptamers are single-stranded oligonucleotides developed through systemic evaluation of ligand by exponential enrichment process (SELEX) with a high affinity toward the target molecule . They have advantages in terms of stability, cost, shelf-life, and ease of chemical modifications compared to traditional antibody-based systems. , Furthermore, aptamers can be engineered to have a conformation-switching property that allows them to modulate the label’s position during a binding event when labeled with a redox-active molecule. ,, These properties make conformation-changing aptamers attractive for wash-free, reagent-less, continuous monitoring applications.…”