Magnetic Bead-Based Immunoassay Allows Rapid, Inexpensive, and Quantitative Detection of Human SARS-CoV-2 Antibodies

Abstract

Immunological methods to detect SARS-CoV-2 seroconversion in humans are important to track COVID-19 cases and the humoral response to SARS-CoV-2 infections and immunization to future vaccines. The aim of this work was to develop a simple chromogenic magnetic bead-based immunoassay which allows rapid, inexpensive, and quantitative detection of human antibodies against SARS-CoV-2 in serum, plasma, or blood. Recombinant 6xHis-tagged SARS-CoV-2 Nucleocapsid protein was mobilized on the surface of Ni 2+ magnetic beads and challenged with serum or blood samples obtained from controls or COVID-19 cases. The beads were washed, incubated with anti-human IgG-HPR conjugate, and immersed into a solution containing a chromogenic HPR substrate. Bead transfer and homogenization between solutions was aided by a simple low-cost device. The method was validated by two independent laboratories, and the performance to detect SARS-CoV-2 seroconversion in humans was in the same range as obtained using the gold standard immunoassays ELISA and Luminex, though requiring only a fraction of consumables, instrumentation, time to deliver results, and volume of sample. Furthermore, the results obtained with the method described can be visually interpreted without compromising accuracy as demonstrated by validation at a point-of-care unit. The magnetic bead immunoassay throughput can be customized on demand and is readily adapted to be used with any other 6xHis tagged protein or peptide as antigen to track other diseases.

Development of a Diagnostic Biosensor Method of Hypersensitivity Pneumonitis towards a Point-of-Care Biosensor

“…The use of this equipment was not easy, and only trained personnel could do so; thus, they were made for large-scale use, limiting their potential use for a PoC device. Other initiatives of the use of magnetic beads on 96 well plates have been published [37]. In these methods, magnetic beads were used to support the reaction molecules and let the liquids pass through and not as reaction surfaces and carriers.…”

Pushing the detection limits: strategies towards highly sensitive optical-based protein detection

“…Micro- and nanoparticles have larger surface-to-volume ratios compared to bulk materials, allowing more capture probes to be used for extracting target proteins from sample solutions, thus improving the assay sensitivity. For example, a bead-based immunoassay was developed by Huergo et al taking advantage of magnetic nanoparticles to detect human SARS-CoV-2 antibodies [ 42 ]. First, these MagneHis Ni 2+ magnetic beads were washed twice with Tris-buffered saline with 0.1% Tween ® 20 Detergent (TBST) and resuspended to incubate with purified His-tagged SARS-CoV-2 nucleocapsid N protein.…”

Rapid and Sensitive Inhibitor Screening Using Magnetically Modulated Biosensors

“…Sensors 2021, 21, x FOR PEER REVIEW 2 of 14 well suited for automation, and improve assay sensitivity, magnetic beads-based assays are commonly used in various bioassays and for biosensing applications [15][16][17][18][19]. Previously, we introduced a novel platform that uses magnetically modulated biosensors (MMB) to rapidly detect very low concentrations of antibodies [20], proteins [21], and specific nucleic acid sequences [22][23][24].…”

“…Other inhibitor screening assays that rely on magnetic beads (e.g., flow cytometry) are also used for the high throughput screening of inhibitors [ 14 ]. Because magnetic beads facilitate the separation steps, are well suited for automation, and improve assay sensitivity, magnetic beads-based assays are commonly used in various bioassays and for biosensing applications [ 15 , 16 , 17 , 18 , 19 ].…”