Biomedical Engineering Reference
In-Depth Information
Fig. 11.2.
Flow immunosensor using beads as the solid support. Target displaces
labeled target analog from immobilized antibodies to generate positive fluorescence
signal downstream. Reprinted from Ligler and Taitt (2002) with permission from
Elsevier
to perform. For a review, see Kusterbeck in [1, 2]. Kusterbeck and colleagues
have recently developed a flow immunosensor to detect unexploded ordinance
in the ocean that has been tested mounted on an unmanned, underwater
vehicle (personal communication).
11.4 Fiber Optic Biosensors
Fiber optic biosensors utilize two distinct assay configurations for signal gen-
eration and measurement: the optrode configuration and the evanescent wave
configuration. Both configurations rely on the same principle of total internal
reflection (TIR) for light propagation and guiding. However, optrodes use the
light shining out the end of the fiber to generate a signal either at the dis-
tal face of the fiber or in the medium near the fiber's end, while evanescent
wave sensors rely on the electromagnetic component of the reflected light at
the surface of the fiber core to excite only the signal events localized at that
surface. The penetration depth of the light into the surrounding medium is
much more restricted than for optrodes, while the surface area interrogated is
much larger in comparison to optrodes of equal diameter. The result is that
evanescent wave biosensors require immobilization of the biological recogni-
tion molecules onto the longitudinal surface of the optical fiber core, primarily
