Grating-coupled Waveguides for Biosensing


The pharmaceutical industry currently relies heavily on fluorescence assays for high-throughput screening of new drug candidates. While fluorescence assays are compatible with high-density formats and provide excellent sensitivity, they require special chemistries for the binding of fluorophores to candidate proteins or drugs and furthermore add to the cost and complexity of each assay. This talk will discuss an attractive alternative to fluorescence detection, namely direct binding assays, made possible by a class of special photonic sensors whose optical characteristics change as biological material binds to the sensor surface. The grating-coupled waveguide is one such embodiment of this technology, and will be discussed in some detail. These devices involve a marriage of waveguide and diffraction grating design, selection of materials for optical properties and chemical compatibility, and appropriate instrument design for optical interrogation of the sensor. Examples of sensor and instrument design as well as typical operation will be presented.