Rapid and Efficient Detection of the SARS-CoV-2 Spike Protein Using an Electrochemical Aptamer-Based Sensor.

Andrea Idili,Ruslán Alvarez-Diduk,Claudio Parolo,Arben Merkoçi

doi:10.1021/acssensors.1c01222

Abstract

The availability of sensors able to rapidly detect SARS-CoV-2 directly in biological fluids in a single step would allow performing massive diagnostic testing to track in real time and contain the spread of COVID-19. Motivated by this, here, we developed an electrochemical aptamer-based (EAB) sensor able to achieve the rapid, reagentless, and quantitative measurement of the SARS-CoV-2 spike (S) protein. First, we demonstrated the ability of the selected aptamer to undergo a binding-induced conformational change in the presence of its target using fluorescence spectroscopy. Then, we engineered the aptamer to work as a bioreceptor in the EAB platform and we demonstrated its sensitivity and specificity. Finally, to demonstrate the clinical potential of the sensor, we tested it directly in biological fluids (serum and artificial saliva), achieving the rapid (minutes) and single-step detection of the S protein in its clinical range.

Highlights

The availability of sensors able to rapidly detect SARS-CoV-2 directly in biological fluids in a single step would allow performing massive diagnostic testing to track in real time and contain the spread of COVID-19
We and other researchers have been working on the development of a new type of sensing technology that can provide a precise quantitative response at the point of care: electrochemical aptamer-based (EAB) sensors.[22−27] This technology relies on the signal produced by a binding-induced conformational change of a redox reporter-modified aptamer on a gold electrode surface (Figure 1B)
A variation in the target concentration induces a change in the aptamer conformation, which in turn changes the position of the redox reporter relative to the electrode surface, generating a quantitative electrochemical signal.[28−32] The precise analytical response of the EAB sensor is coupled with their quick response time and extremely simple operation, making them ideal diagnostic devices for COVID-19 monitoring through high-frequency testing

Summary

Introduction

The availability of sensors able to rapidly detect SARS-CoV-2 directly in biological fluids in a single step would allow performing massive diagnostic testing to track in real time and contain the spread of COVID-19. Current molecular approaches to infectious disease diagnosis are not rapid and decentralized enough to keep up with the spread rate of a highly infectious pathogen in a globalized world.[12,13] For example, the current gold standard technique used to diagnose COVID-19 is the polymerase chain reaction (PCR), which provides high sensitivity and specificity through the direct quantification of the viral RNA This is a crucial clinical parameter to estimate the stage of the infection and to discover asymptomatic patients (i.e., people infected with COVID-19 that cannot be identified due to the absence of symptoms).[14] Despite these clinical advantages, the PCR requires trained personnel, expensive equipment, delicate reagents, and a relatively long procedure, which hamper its use for frequent testing (multiple times per week)[15] and in low-resource settings.[9,10,16] These disadvantages make PCR too slow for the immediate identification of infected asymptomatic individuals, leading to delays in the application of containment measures allowing the virus to spread further.[15] As an alternative to the PCR, lateral flow immunoassays (LFIAs) provide a more rapid response at the point of care,[17] but their lower sensitivity and specificity relegate them primarily for end-point serologic applications (i.e., the detection of anti-SARS-CoV-2 antibodies weeks after getting infected).[18] Even the most recent LFIAs for antigenic testing have considerably lower analytical performance (compared to the PCR), leading to delayed and qualitative diagnosis, which. Here, we describe the development and characterization of a new EAB sensor against the SARSCoV-2 S protein and its ability to recognize the target in undiluted samples (serum and artificial saliva) in its clinical range

Objectives

Results

Conclusion