Label-free Optical Antibody Testing Kit Based on a Self-assembled Whispering-gallery-mode Microsphere.

The appearance of antibodies in blood is a critical signal to suggest the infection. A rapid and accurate detection method for the antibody is significant to the disease diagnosis, especially for the epidemic. To this end, a highly sensitive whispering-gallery-mode (WGM) optical testing kit is designed and fabricated for detecting the specific immunoglobulin antibodies. The key component of the kit is a silica self-assembled microsphere decorated with the nucleocapsid proteins (N-proteins) of the SARS-CoV-2 virus. After the N-protein antibody immunoglobulin G (N-IgG) and immunoglobulin M (N-IgM) solutions being injected into the kit, the WGM red-shifts due to the antigen-antibody reaction. The wavelength displacement rates are proportional to the concentrations of these two antibodies from 1 µg/ml to 100 mg/ml. A good specificity of the kit was demonstrated by the non-specific human immunoglobulin G (H-IgG) and immunoglobulin M (H-IgM). This article is protected by copyright. All rights reserved.