Employing a Redox Reporter-Modified Self-Assembly Monolayer in Electrochemical Aptamer-Based Sensors to Enable Calibration-Free Measurements

Electrochemical aptamer-based (E-AB) sensors suffer from sensor-to-sensor signal variations due to the variation in the total number of probes immobilized on the sensor surface, the effective working area, and the heterogeneity properties of the electrode surface, thus requiring a calibration step prior to each measurement. This is impractical, if not possible, for some cases, e.g., in a complex matrix including blood samples. In response, we propose a calibration-free approach to achieve the measurement of biorelevant small-molecule and protein analytes. Specifically, we employed one reporter labeled onto an aptamer (e.g., methylene blue) for redox signaling, and the other reporter (e.g., ferrocene) was modified onto a self-assembly monolayer as a reference signal. By taking the ratio of the two signals, we achieved a much improved baseline stability and sensor-to-sensor reproducibility, which allows the calibration-free measurement of the analysis of the respective targets, including doxorubicin, vancomycin, and thrombin in both simple buffer and even directly complex samples including serum and whole blood.