USE OF DIODE-LASERS IN AN EVANESCENT-WAVE IMMUNOSENSOR FOR STATIONARYAND TIME-RESOLVED DETECTION OF ANTIGENS

A compact and inexpensive fiber-optic evanescent wave immunosensor is presented which uses a diode laser as excitation source both in contin uous wave measurements as well as in time-resolved experiments. The co ntinuous wave laser operates at 657 nm utilizing a commercially availa ble dye-conjugated polyclonal antibody. Time-resolved experiments with a diode laser emitting at 674 nm were carried out with two fluorescen t dyes, which have nearly identical absorption and emission wavelength s, but differ in their fluorescence lifetimes. This shows the possibil ity of detecting several molecules simultaneously, which are tagged wi th so-called 'multiplex dyes', by identifying the different fluorescen ce lifetimes. Using a new rhodamine dye a successful test of observing the time-resolved binding process between immobilized antibodies and dye-conjugated antigens is reported.