Sandwich-type electrochemical aptamer-based sensor for rapid nanomolar detection of anesthetic drug procaine in biofluids

It is important to develop clinical point-of-care testing (POCT) methods to avoid side effects and even fatalities due to anesthetic drug overdose. Due to their inherent advantages (e.g. ease of modification, thermal stability, and low cost), electrochemical aptamer-based (EAB) sensors are promising alternatives to conventional analytical methods. However, most of the current methods require some complex modification steps for the preparation of electrodes or signal probes as well as the indirect measurement of signals, and the application of these methods as POCT devices remains a challenge. In this work, a sandwich-type EAB sensor was developed for the direct determination of procaine in biofluids. The original aptamer was split into two segments, with one fragment modified with thiol and the other modified with a redox label. The detection process was rapid as conformational changes occur almost instantaneously when the aptamer binds to the target. Moreover, the binding properties of the aptamer towards the target were characterized by circular dichroism spectroscopy, molecular docking simulations and apparent electron transfer rates test. The simple, cost-effective and reagentless sandwich-type EAB sensor achieved nanomolar detection of procaine with a limit of detection (LOD) of 1.9 nM, 5.4 nM and 3.3 nM in buffer, 5 % urine and 2.5 % serum, respectively. This work is expected to play a role in the field of clinical drug analysis.