Rapid multiplex assay of SARS-CoV-2 antigens based on magnetic Janus photonic barcodes

Abstract

SARS-CoV-2 has been causing severe impacts on all aspects of society for more than three years. Antigen immunoassay is the main detection method of SARS-CoV-2 at present. Here, a magnetic photonic crystal microsphere with a Janus structure is designed for synchronous detection of SARS-CoV-2-associated antigens. One hemisphere of the Janus microsphere is a photonic crystal assembled by silica nanoparticles, where the structural color serves as the encoding basis for multiplex detection and the surface is functionalized with the capture antibodies. The other hemisphere of the Janus microsphere is assembled by magnetic nanoparticles, allowing the controlled movement of the microspheres in a magnetic field, thereby enhancing antigen capture efficiency. It is demonstrated that this ingeniously designed detection platform can rapidly and simultaneously detect spike protein and nucleocapsid protein of SARS-CoV-2 based on a double-antibody sandwich immunoassay strategy. The limit of detection (LOD) is 0.478 ng/mL for spike protein and 0.255 ng/mL for nucleocapsid protein. Hence, the Janus photonic barcodes provide a new avenue for multiplex detection of SARS-CoV-2-associated antigens and have the potential to be utilized in the assay of other disease-related biomarkers.