Single fiber biosensors

Fig. 6. Types of optoelectronic biosensors based on fiber optics. R — chemically sensitive reagent, (a) Bifurcated fiber optic sensor (b) single fiber optic with a beam splitter for separation of incident and reflected light (c) single fiber optic in which the reagent phase is coated on the optic.

Figure 5. TNT competitive immunoassay on fiber optic biosensor. A single fiber optic probe was exposed to various solutions containing Cy5-TNB(7.5 ng/ml) + TNT (0-50 ng/ml). Concentrations of TNT (ng/ml) were A=0, B=l, C=5,D=10, E=50.

Trautman J K, Macklin J J, Brus L E and Betzig E 1994 Near-field spectroscopy of single molecules at room temperature Nature 369 40-2 Arnold M A 1991 Fluorophore- and chromophore-based fiber optic biosensors Biosensor Principles and Applications ed L J Blum and P R Goulet (New York Dekker) pp 195-211... 

Wohltjen H, Barger WR, Snow AW, Jarvis NL (1985) A vapor-sensitive chemiresistor fabricated with planar microelectrodes and a Langmuir-Blodgett organic semiconductor film. IEEE Trans Electron Dev ED-32 1170-1174 Wolfbeis OS (1991) Fiber optic chemical sensors and biosensors, vol 1. CRC, Boca Raton, FL Wolfbeis OS (1992) Fiber optic chemical sensors and biosensors, vol 2. CRC, Boca Raton, FL Wolfbeis OS (2005) Materials for fluorescence-based optical chemical sensors. J Mater Chem 15 2657-2669 Wollenstein J, Plaza JA, Can6 C, Min Y, Bottner H, Tuller HE (2003) A novel single chip thin film metal oxide array. Sens Actuators B 93 350-355... 

FIGURE 17 Principle of DNA fiber-optic biosensors, (a) Single-strand DNA probe molecules, with a sequence complementary to one strand of the target DNA sequence, are immobilized onto the fiber, (b) The fluorescent-labeled sample DNA molecules are first dehybridized and the fiber is dipped into the sample solution, (c) After hybridization, the complementary strands of the target DNA are attached to the probe DNA on the fiber and a fluorescence signal is obtained. 

CNTs are also widely used in actuators [168-171], The addition of CNTs to PANI fibers increased the electromechanical actuation because the CNTs improved the mechanical, electronic and electrochemical properties of the PANI fibers [172-174], Composites based on CNTs are studied for a variety of sensor applications [175-177], For example, polypyrrole or PANI deposited on single-walled CNT networks that can be used as solid state pH sensors [178], A DNA sensor was created fi om a composite of polypyrrole and CNTs fimctionalized with carboxylic groups to covalently immobilize DNA onto CNTs [179], In general, the presence of CNTs tends to increase the overall and selectivity of biosensors, The thermal transport properties of polymer composites can be improved with the addition of CNTs due to the excellent thermal conductivity of CNTs, Such composite are quite attractive for usages as printed circuit boards, connectors, thermal interface materials, heat sinks, lids, housings, etc, [92,180],... 

Nanoporous platforms recently have found utility in the fields of plasmonics and optical detection. Nanoporous gold fllms and metallic-coated nanopores - have been applied to techniques like surface-plasmon resonance (SPR) and surface-enhanced Raman spectroscopy (SERS). Additionally, nanoporous metal has been demonstrated to enhance single-molecule fluorescence intensity of immobilized fluorophores due to the enhanced localized plasmon field present within the nanopores. Optically transparent alumina membranes have been developed and found utility as optical biosensors. Additionally, nanoporous gold has been demonstrated to optically detect Hg + ions at concentrations smaller than parts per trillion. A fiber-optic ultrasound generator has been developed from the excitation of gold nanopores with a nanosecond laser. ... 

Zhao, X. Lu, X. Tze, W.T.I. Wang P. (2010). A Single Carbon Fiber Microelectrode with Branching Carbon Nanotubes for Bioelectrochemical Processes. Biosensors and Bioelectronics Vol.25, No.lO, Quly 2010), pp. 2343-2350, ISSN 09565663... 

NADH can also be determined in vivo with an optical fiber using time-resolved fluorescence measurements [209]. This new technique exploits the rapid decrease in fluorescence over a few nanoseconds, and also eliminates the reduction in fluorescence by the optical fiber. The apparatus is shown in Figure 4.34. The excitation beam is provided by a sub-nanosecond nitrogen laser (337 nm). This excitation beam and die emitted fluorescence spectrum are transmitted by a single optical fiber with a diameter of 200 p.m. If NADH concentrations can be directly measured in vivo then a wide variety of biosensors can be envisaged that exploit the enzymatic redox reactions involving this cofactor. 

The use of the emission of light from the reactions of some organic molecules is a significant contribution in the field of biosensors. This is especially important because the need for an excitation source is eliminated, and a single optical fiber is required to carry the light from the reaction to the detector. The measuring device is simpler (no excitation beam and no reference beam) and much more reliable. 

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