Electrochemical Detection of a Few Copies of Unamplified SARS-CoV-2 Nucleic Acids by a Self-Actuated Molecular System

Abstract

The existing electrochemical biosensors lack controllable and intelligent merit to modulate the sensing process upon external stimulus, leading to challenges in analyzing a few copies of biomarkers in unamplified samples. Here, we present a self-actuated molecular-electrochemical system that consists of a tentacle and a trunk modification on a graphene microelectrode. The tentacle that contains a probe and an electrochemical label keeps an upright orientation, which increases recognition efficiency while decreasing the pseudosignal. Once the nucleic acids are recognized, the tentacles nearby along with the labels are spontaneously actuated downward, generating electrochemical responses under square wave voltammetry. Thus, it detects unamplified SARS-CoV-2 RNAs within 1 min down to 4 copies in 80 μL, 2–6 orders of magnitude lower than those of other electrochemical assays. Double-blind testing and 10-in-1 pooled testing of nasopharyngeal samples yield high overall agreement with reverse transcription-polymerase chain reaction results. We fabricate a portable prototype based on this system, showing great potential for future applications.

Recent advancements in nucleic acid detection with microfluidic chip for molecular diagnostics

“…Electrochemical detection is a powerful analytical method for POCT applications because it is fast, simple to manufacture, low cost, portable, and easy to control. The specific electrical signal can be generated by functionalized modifications of the electrode, such as immobilized probes, enzymes, and aptamers, which bind specifically to the amplification product [ [89] , [90] , [91] ]. Electrochemical detection is well suited to miniaturization and integration with microfluidics.…”

Achieving broad availability of SARS-CoV-2 detections via smartphone-based analysis

“…Compared to optical detections, the electrochemical analysis of the virus may have many advantages. For instance, some electrochemical sensors can detect non-nucleic acids such as antigens and antibodies while detecting nucleic acids [ 139 ]; Some electrochemical analyses can recognize unamplified SARS-CoV-2 RNAs so fast and sensitive that 4 copies of the virus in 80 μL saliva can be detected within 1 min [ 149 ]; Some reported electrochemical probes even have higher sensitivity than the PCR test [ 150 ], but most of these approaches require further validation with clinical samples. Although these methods have been considered low-cost strategies, the frequently used signal output instrument (Sensi-smart) in combination with a smartphone is relatively expensive (about 15,000 US dollars or more) [ [151] , [152] , [153] ].…”

Total Bioaerosol Detection by Split Aptamer-Based Electrochemical Nanosensor Chips

“…Standard electrochemical biosensors based purely on aptamer–ATP interactions are usually not sensitive enough to meet the challenge of bioaerosol detection. Therefore, considerable efforts have been directed toward coupling with nanomaterials that amplify the electrochemical signal to achieve acceptable performance. , Recently, metal carbides and nitrides (MXenes) have emerged as promising transducing materials in biosensing due to their high stability and high metallic conductivity. − However, integrating DNA aptamers with MXenes-based composite materials for electrochemical bioaerosols sensing has not yet been demonstrated.…”

“…Therefore, considerable efforts have been directed toward coupling with nanomaterials that amplify the electrochemical signal to achieve acceptable performance. 23,24 Recently, metal carbides and nitrides (MXenes) have emerged as promising transducing materials in biosensing due to their high stability and high metallic conductivity. detection of ATP in bioaerosols.…”