ABSTRACT
The COVID-19 pandemic raises the need for diverse diagnostic approaches to rapidly detect different stages of viral infection. The flexible and quantitative nature of single-molecule imaging technology renders it optimal for development of new diagnostic tools. Here we present a proof-of-concept for a single-molecule based, enzyme-free assay for detection of SARS-CoV-2. The unified platform we developed allows direct detection of the viral genetic material from patients' samples, as well as their immune response consisting of IgG and IgM antibodies. Thus, it establishes a platform for diagnostics of COVID-19, which could also be adjusted to diagnose additional pathogens.
Subject(s)
COVID-19 Nucleic Acid Testing/methods , COVID-19 Serological Testing/methods , COVID-19/diagnosis , SARS-CoV-2/immunology , Single Molecule Imaging/methods , Viral Proteins/genetics , Antibodies, Viral/blood , Base Sequence , COVID-19/blood , COVID-19/immunology , COVID-19/virology , COVID-19 Nucleic Acid Testing/standards , COVID-19 Serological Testing/standards , Enzyme-Linked Immunosorbent Assay , Humans , Immune Sera/chemistry , Immunoglobulin G/blood , Immunoglobulin M/blood , Nasopharynx/virology , Polyproteins/blood , Polyproteins/genetics , RNA, Viral/blood , RNA, Viral/genetics , SARS-CoV-2/genetics , Sensitivity and Specificity , Single Molecule Imaging/instrumentation , Viral Proteins/bloodABSTRACT
The outbreak of the coronavirus disease (COVID-19) pandemic caused by the novel coronavirus (SARS-CoV-2) has been declared an international public health crisis. It is essential to develop diagnostic tests that can quickly identify infected individuals to limit the spread of the virus and assign treatment options. Herein, we report a proof-of-concept label-free electrochemical immunoassay for the rapid detection of SARS-CoV-2 virus via the spike surface protein. The assay consists of a graphene working electrode functionalized with anti-spike antibodies. The concept of the immunosensor is to detect the signal perturbation obtained from ferri/ferrocyanide measurements after binding of the antigen during 45 min of incubation with a sample. The absolute change in the [Fe(CN)6]3-/4- current upon increasing antigen concentrations on the immunosensor surface was used to determine the detection range of the spike protein. The sensor was able to detect a specific signal above 260 nM (20 µg/mL) of subunit 1 of recombinant spike protein. Additionally, it was able to detect SARS-CoV-2 at a concentration of 5.5 × 105 PFU/mL, which is within the physiologically relevant concentration range. The novel immunosensor has a significantly faster analysis time than the standard qPCR and is operated by a portable device which can enable on-site diagnosis of infection.