Detection of anti-SARS-CoV-2 antibody for the diagnosis of past-COVID-19 infection cases using a liquid-crystal-based immunosensor

ABSTRACT

Here, we developed a liquid crystal (LC)-based immunosensor for the sensitive and selective detection of anti-severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) nucleocapsid (N) protein antibodies. LC molecules were aligned parallel to the anisotropic gold nanostructure to induce uniform alignment, and a uniform texture was observed under a polarised optical microscope (POM). After the antigen was immobilised on the nanostructure, the surface was incubated with the antibodies to form antigen-antibody complexes. This led to interference in the uniform alignment of the LC molecules, and a random texture was observed under POM. However, when the surface was incubated with control proteins, the alignment of the LC molecules did not change and a uniform texture was observed under POM. This texture change of the LC optical images was evaluated as quantified values using grey-scale intensity measurements. The lower detection limit was determined to be 100 ng/mL in phosphate-buffered saline (PBS) solution, which is lower than the clinically relevant concentration in the µg/mL range. The developed LC-based immunosensor has high sensitivity and selectivity for the detection of the anti-SARS-CoV-2N protein antibody, which can be easily detected with a small sample volume of 2 µL.

Graphical abstract

KEYWORDS:

• Liquid crystal (LC)
• 4-cyano-4’-pentylbiphenyl (5CB)
• COVID-19
• SARS-CoV-2 antibody
• immunosensor

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the Basic Science Research Program of the National Research Foundation of Korea (NRF) funded by the Ministry of Education under [Grant NRF- 2019R1A2C1003862].