High‐Affinity Dimeric Aptamers Enable the Rapid Electrochemical Detection of Wild‐Type and B.1.1.7 SARS‐CoV‐2 in Unprocessed Saliva

Abstract

We report as imple and rapid saliva-based SARS-CoV-2 antigen test that utilizes an ewly developed dimeric DNAa ptamer,d enoted as DSA1N5, that specifically recognizes the spike proteins of the wildtype virus and its Alpha and Delta variants with dissociation constants of 120, 290 and 480 pM, respectively,a nd binds pseudotyped lentiviruses expressing the wildtype and alpha trimeric spike proteins with affinity constants of 2.1 pM and 2.3 pM, respectively.T o develop ah ighly sensitive test, DSA1N5 was immobilized onto gold electrodes to produce an electrochemical impedance sensor,which was capable of detecting 1000 viral particles per mL in 1:1d iluted saliva in under 10 min without any further sample processing. Evaluation of 36 positive and 37 negative patient saliva samples produced aclinical sensitivity of 80.5 % and specificity of 100 %a nd the sensor could detect the wildtype virus as well as the Alpha and Delta variants in the patient samples,w hich is the first reported rapid test that can detect any emerging variant of SARS-CoV-2.

Peptide-based simple detection of SARS-CoV-2 with electrochemical readout

“…Previous reports have found that Electrochemical Impedance Spectroscopy (EIS)-based biosensors rapidly detect bioreceptors associated with SARS-CoV-2 infection, with high sensitivity, specificity and reliability [ [8] , [9] , [10] , [11] , [12] , [13] , [14] , [15] , [16] , [17] ]. In such biosensors, bioreceptors are anchored on the working electrode surface to directly bind to target molecules specifically, generating changes in the interfacial properties in a concentration-dependent manner [ [18] , [19] , [20] ].…”

CRISPR-Cas12a-mediated label-free electrochemical aptamer-based sensor for SARS-CoV-2 antigen detection

“…These drawbacks thereby result in potential tradeoffs in terms of sensitivity, specificity and user-friendliness. On the other hand, aptamers, known as “chemical antibodies”, have been recommended as a powerful class of bioreceptors with several features of high specificity and affinity, reliable and cost-effective synthesis, ease of modification, and excellent feasibility to combine with many DNA-based reactions for signal amplification [36] , [37] , [38] . These advantages enable aptamers to be promising bioreceptors, with a wide range of applications for biosensors [39] , [40] , [41] , [42] , [43] , [44] , [45] , [46] , [47] .…”

Aptamer-based biosensors for virus protein detection

“…The selectivity and affinity of monovalent aptamers are easily subjected to sample conditions, including temperature, PH, ionic strength, interference, viscosity, etc [ 198 ]. Several strategies could be taken to address this issue: 1) Using multivalent spatial recognition patterns [ 114 , 124 ]. Generally, multivalent aptamers exhibit more excellent recognition and binding abilities than monovalent aptamers.…”

“…As one of the most sensitive transduction approaches, electrochemical impedance spectroscopy (EIS) has been widely applied for sensing. Zhang et al [ 114 ] first reported a bivalent aptamer (DSA1N5) nanoprobe-based EIS aptasensor, Cov-eChip, to detect original SARS-CoV-2, Delta, and Alpha variants of this virus in unprocessed saliva. In this sensor, the DSA1N5 bivalent aptamer was engineered by ligating two monomers (MSA1 and MSA5), and it was immobilized on gold electrodes to generate an electrochemical impedance signal ( Fig.…”