Integrating Waveguide Technologies

Figure 1. Schematic of the Integrating Waveguide Biosensor

Figure 2. Schematic of Creatv’s spectrofluorometer concept

Creatv’s bio-detection  products are based on the Integrating Waveguide Biosensor developed by Naval Research Laboratory and related technologies developed by Creatv.  One detection method is based on capturing the analyte on the surface of a waveguide and tagging the analyte with a fluorescent dye (such as in a sandwich immunoassay). A light source appropriate to the fluorescent dye illuminates the optical waveguide at a 90 degree angle. The emitted fluorescent signal is efficiently gathered by the waveguide and exits from the end of the  waveguide. The fluorescence signal is sent to the detector via a set of lenses and filters. The schematic is shown in the figure where the waveguide is a flow through capillary tube and the analyte is captured on the inside surface of the capillary tube.

This detection method was invented by Dr. Frances Ligler and colleagues at the Naval Research Laboratory and has been licensed to Creatv MicroTech [Feldstein et al. 2000] Dr. Ligler developed two previous biosensors, optical fiber and array biosensors using evanescent wave illumination. The Integrating Waveguide Biosensor has been shown by Ligler to be about a factor 100 more sensitive by Ligler than her two previous biosensor technologies. [Ligler et al. 2002] The Integrating Waveguide Biosensor instrument is based on this concept.

Creatv developed assays that demonstrated that as few as one captured E. coli O157 on the surface of the waveguide is above the limit of detection.

Creatv also developed an instrument, called Signalyte^TM, for detecting fluorescent dyes in solution. The schematic is shown in Figure 2. The sample holding cuvette has a lens at the end. The sample and the cuvette together act as a waveguide. The fluorescence excitation light source illuminates the waveguide at 90 degrees. The fluorescence signal is efficiently gathered by the waveguide. The signal passes through a set of lenses and optical filter before reaching the detector.

Signalyte^TM is applicable for wide range of assays. Examples of applications are:
• Read liquid phase sandwich immunoassay results such as those using magnetic beads.
• Read end point PCR results. Since the instrument is very sensitive, the number of PCR cycles can be reduced.

References

Feldstein, M. J.,MacCraith, B. D., Ligler, F. S., Integrating Multi-waveguide Sensor, U.S. Patent No. 6,137,117 issued on October 24, 2000.
Ligler, F. S., Breimer, M., Golden, J. P., Nivens, D. A., Dodson, J. P., Green, T. M., Haders, D. P. & Sadik, O. A. Integrating waveguide biosensor. Anal. Chem. 74:713-719 (2002).