Label-free optical antibody testing kit based on a self-assembled whispering-gallery-mode microsphere

Area of Science:

• Biomedical Engineering
• Nanotechnology
• Immunology

Background:

• Antibody detection is crucial for diagnosing infections, particularly during epidemics.
• Rapid and accurate methods are needed for timely disease diagnosis.
• Specific immunoglobulin G (IgG) and immunoglobulin M (IgM) antibodies are key indicators of viral infections like SARS-CoV-2.

Purpose of the Study:

• To design and fabricate a highly sensitive whispering-gallery-mode (WGM) optical testing kit for detecting specific immunoglobulin antibodies.
• To utilize SARS-CoV-2 nucleocapsid proteins (N-proteins) for antibody detection.
• To establish a rapid and accurate diagnostic tool for epidemic surveillance.

Main Methods:

• Fabrication of a silica self-assembled microsphere decorated with SARS-CoV-2 N-proteins.
• Injection of N-protein antibody immunoglobulin G (N-IgG) and immunoglobulin M (N-IgM) solutions into the WGM optical testing kit.
• Monitoring the red-shift of WGM due to antigen-antibody reactions and correlating wavelength displacement with antibody concentration.

Main Results:

• The WGM optical testing kit demonstrated high sensitivity in detecting N-IgG and N-IgM.
• Wavelength displacement rates were found to be proportional to antibody concentrations in the range of 1 to 100 μg/mL.
• The kit exhibited good specificity, distinguishing between specific viral antibodies and nonspecific human immunoglobulins (H-IgG, H-IgM).

Conclusions:

• The developed WGM optical testing kit offers a promising approach for rapid and sensitive detection of specific SARS-CoV-2 antibodies.
• The proportionality between wavelength shift and antibody concentration allows for quantitative analysis.
• This technology has significant potential for application in epidemic diagnosis and disease monitoring.