Detection of Antigen–Antibody Reaction Using Si Ring Optical Resonators Functionalized with an Immobilized Antibody-Binding Protein

We propose the integrated biosensor chip using Si ring resonators, where different receptor is immobilized on each sensor. Signal detection is carried out by the matrix of light-input and detection waveguides, which are respectively connected to laser diodes and photodetectors. The Si rings are arranged at the cross points. The unique point of our work is to use the silicon-binding protein (designated Si-tag), which binds to SiO2 surface, as an anchoring molecule to immobilize bioreceptor on the Si rings in an oriented manner. In the integrated biosensor chip, many kinds of Si-tag-receptor fusions are required for high-throughput detection of analyte. In this paper, the Si ring biosensors were functionalized with various antibodies using the Si-tagged protein A as an intermediate binder, and the label-free detection of antigen have been achieved. We have developed the rapid functionalization method of Si-ring resonators with antibodies using Si-tagged protein A. Since various kinds of antibody can be used as receptors for biosensing, this method promises to realize the integrated biosensors for high-throughput analyte detection.