Fluorescent optical sensors lasers

Wolfbeis O.S., Fluorescence-based optical sensors for biomedical applications, In Scheggi A.M.V., Martelluci, S., Chester, A.N., Pratesi, R. (Eds.), Biomedical Optical Instrumentation and laser-Assisted Biotechnology, Kluwer Academic Publishers, 1996, p.327-337. 

Optical and laser technologies also offer the prospect for improvements in fluorescence and phosphorescence determinations. An important development is the use of fluorescence and phosphorescence with optical fiber sensors. 

Perhaps the most well-recognized fluorescent dye for detection of DNA hybridization is ethidium bromide (EtBr). EtBr is a cationic phenanthridinium compound that can bind to DNA by intercalation. This dye has an excitation maxima at 518 nm when bound to double-stranded DNA (dsDNA). Excitation of EtBr is often done by use of an argon ion laser, making this fluorophore a viable choice for applications in optical sensors as well as confocal scanning laser microscopy and fluorometry [41]. The structure of ethidium bromide is shown in Fig. 6. 

Most present-day fiber-optic sensors use linear diode arrays combined with optical gratings and measure the absorption, transmission, fluorescence, and reflection in UV, visible, and NIR regions (see Table 3.1). Light travels to the sampling probe via one fiber-optic cable and returns to the instrument via a second. Laser excitation permits long-distance transmission of excitation radiation to get a useful signal from the sample. 

Industrial Applications Fiber optic sensor for sol-gel material planar laser-induced fluorescence (PLIF) measurements in aqueous flows ... 

A pH optical sensor can be constructed to measure the fluorescence emitted by fluoresceinamine immobilized on the tip of an opfical fiber [10]. An argon laser excites the sample at 488 nm with a beam intensity of 1.5 W at the tip of the fiber. The response to pH is... 

An NIR biosensor coupled with an NIR fluorescent sandwich immunoassay has been developed. 109 The capture antibody was immobilized on the distal end of an optical fiber sensor. The probe was incubated in the corresponding antigen with consecutive incubation in an NIR-labeled sandwich antibody. The resulting NIR-labeled antibody sandwich was excited with the NIR beam of a laser diode, and a fluorescent signal that was directly proportional to the bound antigen was emitted. The sensitivity of the technique increased with increasing amounts of immobilized receptor. There are several factors involved in the preparation of the sandwich type biosensor. A schematic preparation of the sandwich optical fiber is shown in Figure 7.14. 

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