USE OF 3 LONGER-WAVELENGTH FLUOROPHORES WITH THE FIBEROPTIC BIOSENSOR

With the availability of fluorescent dyes that are excited above 600 nm and couple easily to proteins, portable biosensors are becoming a reality. The use of diode lasers to excite these dyes permits systems to be made small and lightweight. An added benefit to switching to the near-infrared (NIR) regime is the reduction in background fluorescence from environmental and clinical samples. Previously, an evanescent wave biosensor was developed at the Naval Research Laboratory (NRL) using tetramethylrhodamine isothiocyanate as the fluorescent tag. Using this biosensor, toxins and other proteins have been detected down to 1 ng ml(-1) and bacteria to 3000 cells ml(-1). In this study, two new biosensors have been constructed using the same design with only selected components changed for detection of other fluorophores. An antigen (goat IgG) is labelled with one of three fluorophores: tetramethylrhodamine isothiocyanate, Cy5 and a near-infrared dye. The direct binding of each labelled antigen to an antibody-coated fiber-optic probe is measured. Comparisons of signal magnitudes, level of detection achieved, and photobleaching have been performed.