Planar optic biosensor

Seo et al. (1999) used a planar optic biosensor that measures the phase shift variation in refractive index due to antigen binding to antibody. In this method, they were able to detect S. enterica serovar T) himurium with a detection limit of 1 x 10 cfu/ml. When chicken carcass fluid was inoculated with 20 cfu/ml, the sensor was able to detect this pathogen after 12 h of nonselective enrichment. A compact fiber optic sensor was also used for detection of S. T) himurium at a detection limit of 1 X 10" cfu/ml (Zhou et al., 1997, 1998) however, its efficacy with food samples is unproven. Later, Kramer and Lim (2004) used the fiber optic sensor, RAPTOR , to detect this pathogen from spent irrigation water for alfalfa sprouts. They showed that the system can be used to detect Salmonella spiked at 50 cfu/g seeds. An evanescent wave-based multianalyte array biosensor (MAAB) was also employed for successful testing of chicken excreta and various food samples (sausage, cantaloupe, egg, sprout, and chicken carcass) for S. T) himurium (Taitt et ah, 2004). While some samples exhibited interference with the assay, overall, the detection limit for this system was reported to be 8 x 10 cfu/g. 

While planar optical sensors exist in various forms, the focus of this chapter has been on planar waveguide-based platforms that employ evanescent wave effects as the basis for sensing. The advantages of evanescent wave interrogation of thin film optical sensors have been discussed for both optical absorption and fluorescence-based sensors. These include the ability to increase device sensitivity without adversely affecting response time in the case of absorption-based platforms and the surface-specific excitation of fluorescence for optical biosensors, the latter being made possible by the tuneable nature of the evanescent field penetration depth. 

The goal of this chapter will be to provide an overview of the use of planar, optically resonant nanophotonic devices for biomolecular detection. Nanophotonics23 24 represents the fusion of nanotechnology with optics and thus it is proposed that sensors based on this technology can combine the advantages of each as discussed above. Although many of the issues are the same, we focus here on optical resonance rather than plasmonic resonance (such as is used in emerging local SPR and surface-enhanced Raman spectroscopy-based biosensors). 

H. Gao, M. Sanger, R. Luginbiihl, and H. Sigrist, "finmunosensing with Photo-Immobilized Immunoreagents on Planar Optical Wave Guides," Biosensors Bioelectronics 10, 317-328 (1995). 

Fibre optic-based flow-through optical biosensors The dramatic advances in fibre optic development in die last decade have promoted construction of sensors where radiation, whether emitted, transmitted or reflected, is conducted fi-om the sample to the detection system. The wide variety of available optical waveguide types (solid rods, hollow cylinders, micro-planar geometries) has been used with varying success in sensor development. 

Hofmann, O., Viorin, G., Niedermann, P., Manz, A., Three-dimensional microfluidic confinement for efficient sample delivery to biosensor surfaces. Application to immunoassays on planar optical waveguides. Anal. Chem. 2002,74, 5243-5250. 

Schmitt K, Schirmer B, Hoffmann C, Brandenburg A, Meyrueis P (2007) Interferometric biosensor based on planar optical waveguide sensor chips for label-lree detection of surface bound bioreactions. Biosens Bioelectron 22 2591-2597... 

F. S. (2002) Planar waveguides for fluorescence biosensors. In Optical biosensors Present and future (Ligler, F. S. Rowe Taitt, C. A., eds.). Elsevier, The Netherlands, pp. 95-122... 

In MEMS-based optical biosensor systems, similar configurations are used. Light propagates in free space or is guided by optical fibers or planar optical waveguides. In one setup, only the mechanical stmeture (mirror, cantilever, or reaction chamber) is fabricated on wafers. After... 

The options available for sensor platforms for optical chemical and biosensors are primarily optical fibres, and planar platforms. 

Acetylcholineesterase A 350 pM diameter coherent imaging fiber coated on the distal surface with a planar layer of analyte-sensitive polymer that was thin enough not to affect the fiber s imaging capabilities. It was applied to a pH sensor array and an ACh biosensor array (each contain 6000 optical sensor). Fibers were coated with an immobilized layer of poly (hydroxyethylmethacrylate)-N-flurosceinylacrylamide and AChE-fluorescein isothiocyanate isomer poly (acryloamide-co-N-acryl oxysuccinimide), respectively. The response time of the pH sensor was 2 s for a 0.5 unit increase in pH. The biosensor had a detection limit of 35 pM ACh and a linear response in the range 0.1 mM. [90]... 

In general, a vast number of optical transduction techniques can be used for biosensor development. These may employ linear optical phenomenon (e.g. adsorption, fluorescence, phosphorescence, and polarization) or nonlinear phenomena (e.g. second harmonic generation). The choice of a particular optical method depends on the analyte and the sensitivity needed. Total internal reflection fluorescence (TIRF) has been used with planar and fibre-optic wave-guides as signal transducers in a number of biosensors. 

In Chap. 1 by J. Homola of this volume [1] surface plasmons were introduced as modes of dielectric/metal planar waveguides and their properties were estabhshed. It was demonstrated that the propagation constant of a surface plasmon is sensitive to variations in the refractive index at the surface of a metal film supporting the surface plasmon. In this chapter, it is shown how this phenomenon can be used to create a sensing device. The concept of optical sensors based on surface plasmons, commonly referred as to surface plasmon resonance (SPR) sensors, is described and the main approaches to SPR sensing are presented. In addition, the concept of affinity biosensors is introduced and the main performance characteristics of SPR biosensors are defined. 

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