This Small Grants for Exploratory Research (SGER) award supports research into the applicability of the newly emerging technique of Cavity Ring-Down Spectroscopy - based sensors as probes for biomolecules in the condensed phase, with particular emphasis on potential bioterrorism agents. Four developmental strategies will be pursued to bring the extraordinary sensitivity of Cavity Ring-Down Spectroscopy (CRDS) to biosensor technology. Each has its own potential advantages for implementation, selectivity, and sensitivity. The first approach is the use of a cell whose entrance and exit windows are at Brewster's angle to minimize absorption losses when inserted inside an optical cavity. The purpose of this device is to miniaturize the detector so that very small volumes of liquid can be analyzed. Such a device has particular promise when coupled to microseparations, such as capillary electrophoresis or lab on a chip. The second approach is the use of an optical cavity in which the light makes optical contact with the surroundings by means of an evanescent wave. This device is sensitive to absorption changes at the surface where the optical contact is made. It has the advantage of keeping the light on the inside so that it is immune to questions of turbidity in the medium in contact with the surface. The third approach is the use of surface plasmon resonance (SPR) coupled to CRDS. It is also sensitive to the liquid-surface interface and its value will depend on the ease with which analyte-sensitive probe molecules can be coupled to the metal (gold or silver) surface used in SPR. The fourth approach is the direct contact of the liquid with the two mirrors that constitute the optical cavity. This approach is by far the simplest to implement, and an assessment will be made of what limits its operations, particularly in regard to analyte selectivity. This research could well provide the basis for broad and important applications in the detection and quantification of biomolecules.
This activity is jointly supported by the Office of Multidisciplinary Activities in the Directorate for Mathematical and Physical Sciences and by the Instrumentation and Instrument Development Program in the Division of Biological Infrastructure in the Directorate for Biological Sciences.
