Fast analysis of virus-antibody interaction by common path interferometric microscopy

Interferometric microscopy techniques have been recently developed to detect small particles at the nanoscale without the need for specific labeling. Here, we introduce a highly sensitive, label-free approach on a common path interferometric set-up working on a transmission that amplifies weak scattering signals coming from small particles. Using single-particle tracking analysis, we can track and differentiate viruses and other biotic particles in aquatic environment. Furthermore, we have developed a fast assay based on antibody recognition of targeted virus in solution. We associate changes in diffusion and in the interferometric signal of the detected particles with the immune reaction between antibodies and surface proteins of the virus.