Chiral optical sensing mechanism for detecting antibodies in human blood specific to antigens

Abstract

Due to the current pandemic situation, the need of performing antibody detection is much more than before in bio-related research labs. However, traditional methods of antibody detection, such as ELISA, require cumbersome and complex procedures. Therefore, we decided to perform the detection in optical ways. In this research, we propose a mechanism of antibody detection using plasmon-induced chirality transfer. In our design, gold nanorods (AuNR) would be functionalized with antibodies, and silver nanorods (AgNR) would be functionalized with antigens. By doing so, the formed antibody-antigen bridges would induce the chirality of the whole combined AuNR-AgNR heterodimers and generate circular dichroism (CD) signals. To further enhance the specificity, AuNRs would be dyed with fluorophores so that when the antibody-antigen complexes form, they would emit fluorescent CD signals. However, the CD spectra of biomolecules are usually in the ultraviolet (UV) regime. The optical components working in such a regime are usually expensive. Moreover, UV light is potentially hazardous to biomolecules due to its high photon energy. With the chirality transfer effect, we can utilize metal achiral nanospheres having optical spectra in the visible regime and shift the CD signal peak into the visible regime so that we can just use a visible light spectrometer, which is common and low-cost, to perform the measurement. In our research, we used COMSOL to simulate and test our newly designed methods for antibody detection and then analyze the result comprehensively; in addition, we also designed and constructed a CD spectrometer by ourselves, and performed CD scanning on chiral materials, such as chlorophyll.