Label-free detection of biomolecules by waveguide interferometry

We report on a recently developed highly sensitive instrument for label-free detection of biomolecules based on the principle of a Young interferometer. With this technology, biomolecular interactions can be detected in real-time without elaborate sample preparation using a planar waveguide as sensing element. The binding reaction of the antibody-antigen pair immunoglobulin G and protein G has been studied and an affinity constant of K=2.6*107 M-1 has been determined.