Magnetic beads combined with carbon black-based screen-printed electrodes for COVID-19: A reliable and miniaturized electrochemical immunosensor for SARS-CoV-2 detection in saliva

Abstract

The diffusion of novel SARS-CoV-2 coronavirus over the world generated COVID-19 pandemic event as reported by World Health Organization on March 2020. The huge issue is the high infectivity and the absence of vaccine and customised drugs allowing for hard management of this outbreak, thus a rapid and on site analysis is a need to contain the spread of COVID-19. Herein, we developed an electrochemical immunoassay for rapid and smart detection of SARS-CoV-2 coronavirus in saliva. The electrochemical assay was conceived for Spike (S) protein or Nucleocapsid (N) protein detection using magnetic beads as support of immunological chain and secondary antibody with alkaline phosphatase as immunological label. The enzymatic by-product 1-naphtol was detected using screen-printed electrodes modified with carbon black nanomaterial. The analytical features of the electrochemical immunoassay were evaluated using the standard solution of S and N protein in buffer solution and untreated saliva with a detection limit equal to 19 ng/mL and 8 ng/mL in untreated saliva, respectively for S and N protein. Its effectiveness was assessed using cultured virus in biosafety level 3 and in saliva clinical samples comparing the data using the nasopharyngeal swab specimens tested with Real-Time PCR. The agreement of the data, the low detection limit achieved, the rapid analysis (30 min), the miniaturization, and portability of the instrument combined with the easiness to use and no-invasive sampling, confer to this analytical tool high potentiality for market entry as the first highly sensitive electrochemical immunoassay for SARS-CoV-2 detection in untreated saliva.

The role of the surface ligand on the performance of electrochemical SARS-CoV-2 antigen biosensors

“…Fabiani et al [ 13 ] proposed an electrochemical immunosensor for SARS-CoV-2 detection in saliva. This assay was conceived for the detection of the S1 protein as well as the nucleocapsid protein using magnetic beads (MB) as support (Fig.…”

“…4 Electrochemical antigenic COVID-19 sensors: a magnetic bead–based electrochemical immunosensors for S1 protein detection: change in DPV signal upon viral binding together with selectivity test (reprinted with permission from ref. [ 13 ]). b Electrochemical biosensors, eCoVSense, using glass slides coated with fluorine-doped tin oxide and modified with Au NPs serving for COVID-19 antibody conjugation by physisorption or electrostatic interactions; the same was performed on screen-printed carbon electrodes where antibodies were immobilized [ 36 ] .…”

Electrochemical Biosensors for the Detection of SARS-CoV-2 and Other Viruses

“…Although they may present future use as point-of-care diagnostics, further work still needs to be done in order to miniaturize and lower the cost of these biosensors. Currently, optical, electrochemical, and molecularly imprinted biosensors are being designed for the detection of COVID-19 [143][144][145][146][147][148][149], as seen in Table 1:…”

Nanomaterials to tackle the COVID-19 pandemic

“…Fig. 3 a Real-time electrochemical biosensing of SARS-CoV-2 RNA [61], b magnetic beadsbased assay for the detection of SARS-CoV-2 in untreated saliva [63], c graphene-based FET biosensor for the detection of SARS-CoV-2 [30] Torrente-Rodriguez studied a multiplexed, portable, wireless graphene-based electrochemical biosensor, which was named the SARS-CoV-2 RapidPlex, for the rapid detection and monitoring of the COVID-19. It was reported that this electrochemical biosensor was able to detect viral antigen nucleocapsid protein, IgM and IgG antibodies, and the inflammatory biomarker C-reactive protein (CRP).…”

“…Fabiani et al [63] investigated a miniaturized electrochemical immunosensor to detect the SARS-CoV-2 virus in saliva (Fig. 3b).…”