Subsecond-Resolved Molecular Measurements Using Electrochemical Phase Interrogation of Aptamer-Based Sensors

Abstract

Recent years have seen the development of a number of biosensor architectures that rely on target binding-induced changes in the rate of electron transfer from an electrode-bound receptor. Most often, the interrogation of these sensors has relied on voltammetric methods, such as square-wave voltammetry, which limit their time resolution to a few seconds. Here, we describe the use of an impedance-based approach, which we have termed electrochemical phase interrogation, as a means of collecting high time resolution measurements with sensors in this class. Specifically, using changes in the electrochemical phase to monitor target binding in an electrochemical-aptamer based (EAB) sensor, we achieve subsecond temporal resolution and multihour stability in measurements performed directly in undiluted whole blood. Electrochemical phase interrogation also offers improved insights into EAB sensors' signaling mechanism. By modeling the interfacial resistance and capacitance using equivalent circuits, we find that the only parameter that is altered by target binding is the charge-transfer resistance. This confirms previous claims that binding-induced changes in electron-transfer kinetics drive signaling in this class of sensors. Considering that a wide range of electrochemical biosensor architectures rely on this signaling mechanism, we believe that electrochemical phase interrogation may prove generalizable toward subsecond measurements of molecular targets.

Detection of the SARS-CoV-2 spike protein in saliva with Shrinky-Dink© electrodes

“…Specifically, electrochemical aptamer-based (E-AB) sensors use this strategy to achieve response times on the order of seconds or faster and provide equilibrium results within 30 minutes. 20 The limit of detection (LOD) for E-AB virus sensors depends on the target analyte, aptamer and most importantly, sensor design; the LOD can be brought to lower ranges through amplification methods to accommodate the low concentrations (aM - nM) of analyte present in physiological conditions. 21–23 In 2009, an E-AB was used to detect the nucleocapsid protein of the SARS-CoV virus with a LOD of 2 pg mL −1 , which falls in the lower range of concentrations of detectable viral load in nasopharyngeal and saliva samples.…”

Interrogation of Electrochemical Aptamer-Based Sensors via Peak-to-Peak Separation in Cyclic Voltammetry Improves the Temporal Stability and Batch-to-Batch Variability in Biological Fluids

“…E-AB sensors can be successfully interrogated via chronoamperometry, differential pulse techniques such as square wave voltammetry and differential pulse voltammetry, alternating current voltammetry, or electrochemical impedance spectroscopy . Published reviews discuss the benefits and disadvantages of each of these interrogation techniques. ,, Ultimately, the choice of technique is determined by the final intended application of the E-AB sensor.…”

Nucleic-Acid Driven Cooperative Bioassays Using Probe Proximity or Split-Probe Techniques

“…For quite some time, methods for biomarker quantification with electrochemistry (EC) have been viewed favorably, due to the low cost and adaptability of the instrumentation and its amenability to point-of-care analysis . In recent years, there has been renewed interest in the development of EC biosensors, particularly focusing on analytes that are not EC-active, are not substrates of known enzymes, or are not well-suited for potentiometric measurements; many of these sensors are based on quantifying aptamer or antibody binding events with analytes at electrode surfaces. − Considering the importance of EC assays in analytical chemistry, we chose to elaborate here on recent EC applications that leverage the proximity effect.…”