ABSTRACT
Optical sensors provide significant advantages for in situ monitoring applications due to the optical
nature of the excitation and detection modalities. Fiber-optic sensors are not affected by electromagnetic
interferences from static electricity, strong magnetic fields, or surface potentials. Another advantage of
fiber-optic sensors is the small size of optical fibers, which allow sensing intracellular or intercellular
physiological and biological parameters in microenvironments. Biosensors, which use biological probes
coupled to a transducer, have been developed during the last two decades for environmental, industrial,
and biomedical diagnostics. Extensive research and development activities in our laboratory have been
devoted to the development of a variety of fiber-optic chemical sensors and biosensors [1-9]. Recent
advances in nanotechnology have led to the development of fiber optics-based nanosensor systems
having nanoscale dimensions suitable for intracellular measurements. The possibilities to monitor
in vivo processes within living cells could dramatically improve our understanding of cellular function,
thereby revolutionizing cell biology. The application of a submicron fiber-optic chemical sensor has
been reported [10,11]. Submicron tapered optical fibers with distal diameters between 20 and 500 nm
have been employed to study the submicron spatial resolution achievable using near-field scanning
optical microscopy (NSOM). The combination of NSOM and surface-enhanced Raman scattering
(SERS) has been demonstrated to detect chemicals on solid substrates with subwavelength 100-nm
spatial resolution [12,13]. Submicron optical-fiber probes have been developed for chemical analyses
[14,15]. Nanosensors with antibody probes have been developed and used to detect biochemical targets
inside single cells [16-21].
