Structure-Switching Electrochemical Aptasensor for Rapid, Reagentless, and Single-Step Nanomolar Detection of C-Reactive Protein.

C-reactive protein (CRP) is an acute-phase reactant and sensitive indicator for sepsis and other life-threatening pathologies, including systemic inflammatory response syndrome. Currently, clinical turn-around times for established CRP detection methods take between 30 min to hours or even days from centralized laboratories. Here, we report the development of an electrochemical biosensor using redox probe-tagged DNA aptamers, functionalized onto inexpensive, commercially available screen-printed electrodes. Binding-induced conformational switching of the CRP-targeting aptamer induces a specific and selective signal-ON event, which enables single-step and reagentless detection of CRP in as little as 1 min. The aptasensor limit of detection spans approximately 20-60 nM in 50% human serum with dynamic response windows spanning 1-200 or 1-500 nM ( R = 0.97/ R = 0.98 respectively). The sensor is stable for at least 1 week and can be reused numerous times, as judged from repeated real-time dosing and dose-response assays. By decoupling binding events from the signal induction mechanism, structure-switching electrochemical aptamer-based sensors provide considerable advantages over their adsorption-based counterparts. Our work expands on the retinue of such sensors reported in the literature and is the first instance of structure-switching electrochemical aptamer-based sensors (SS-EABs) for reagentless, voltammetric CRP detection. We hope this study inspires further investigations into the suitability of SS-EABs for diagnostics, which will aid translational R&D toward fully realized devices aimed at point-of-care applications or for broader use by the public.