Improved calibration of electrochemical aptamer-based sensors

Abstract

Electrochemical aptamer-based (EAB) sensors support the real-time, high frequency measurement of pharmaceuticals and metabolites in-situ in the living body, rendering them a potentially powerful technology for both research and clinical applications. Here we explore quantification using EAB sensors, examining the impact of media selection and temperature on measurement performance. Using freshly-collected, undiluted whole blood at body temperature as both our calibration and measurement conditions, we demonstrate accuracy of better than ± 10% for the measurement of our test bed drug, vancomycin. Comparing titrations collected at room and body temperature, we find that matching the temperature of calibration curve collection to the temperature used during measurements improves quantification by reducing differences in sensor gain and binding curve midpoint. We likewise find that, because blood age impacts the sensor response, calibrating in freshly collected blood can improve quantification. Finally, we demonstrate the use of non-blood proxy media to achieve calibration without the need to collect fresh whole blood.

Week-long operation of electrochemical aptamer sensors: New insights into self-assembled monolayer degradation mechanisms and solutions for stability in biofluid at body temperature

“…With more aptamer molecules being incapable of bringing their redox reporter closer to the electrode surface, while still contributing to the redox tag current measured in analyte-free serum, a higher concentration is needed to drive a higher proportion of the unrestrained aptamer population toward the bound state. Of note, MCO sensors still showed appreciable sensor response after 7 days of continuous scanning in serum at 37 ˚C, albeit with large interelectrode error which could significantly impair calibration efforts 44 (see Supplemental Figure S5).…”

Real-Time, In Vivo Molecular Monitoring Using Electrochemical Aptamer Based Sensors: Opportunities and Challenges

“…Using such techniques has enabled the measurement of a number of targets with clinically relevant accuracy and precision. 17,23,26,30,36,49,50 Building on the above attributes, the EAB platform is the only technology demonstrated to achieved hours-long, realtime molecular measurements in the body without relying on the target's intrinsic reactivity, 56 spectroscopic properties, 57 or enzymatic activity. 58 Specifically, the platform has been used to perform real-time measurements of multiple drugs (including antibiotics, 17,49 chemotherapeutics, 23,49,55 and drugs of abuse 53 ) and metabolites (including ATP and phenylalinine 30,31,54 ) in situ in the bodies of live rats (Table 2).…”

“…The resulting data is fit to a Hill–Langmuir isotherm, yielding parameters that enable (B) quantification of data inputted into the Hill–Langmuir equation. Reproduced with permission from ref .…”

“…Fortunately, however, this drift can be corrected using a variety of approaches. ,, The “kinetic differential measurement” (KDM) technique, for example, leverages square wave frequency pairs that, when interrogated sequentially, drift in concert. , Subtracting the normalized peak signals and dividing by their average thus correct for sensor signal loss over time. Using such techniques has enabled the measurement of a number of targets with clinically relevant accuracy and precision. ,,,,,, …”

Challenges in Biomaterials Science for Electrochemical Biosensing and Bioenergy

“…35 Other versatile substitutes are aptamers, oligonucleotides, and peptides designed to bind specifically to a target analyte, often taking advantage of labeled probes. Significant advances have been achieved in the past years, especially regarding the consistent and efficient fabrication of electrochemical aptamerbased biosensors by Xiao and co-workers, 36 as well as these biosensors' calibration, 37 exploring a combined interfacial chemistry using gold electrodes and thiolated DNA probes functionalized with methylene blue as a redox reporter, operating in a target-binding-induced folding fashion, which leads to a current decrease when the ssDNA matching occurs.…”