ABSTRACT
Fiber-optic DNA biosensors are a kind of ana-lytic setups, which convert the Waston-Crick base pairs matching duplex or Hoogsteen’s tri-plex (T/A-T, C/G-C) formation into a readable analytical signals when functionalized single- strands DNA (ssDNA) or double-strands DNA (dsDNA) of interest are immobilized on the sur-face of fiber-optic hybrids with target DNA or interacts with ligands. This review will provide the information about the fiber-optic DNA bio-sensors classified into two categories depend-ing on the end fiber and side fiber with or with-out the labels—label-free fiber-optic DNA bio-sensors and labeled fiber-optic DNA biosensor in recent years. Both are dissertated, and em-phasis is on the label-free fiber-optic DNA bio-sensors. Fiber-optic DNA biosensors had got great progresses because fiber-optic has more advantages over the other transducers and are easily processed by nanotechnology. So fiber- optic DNA biosensors have increasingly at-tracted more attention to research and develop the new fiber-optic DNA biosensors that inte-grated with the “nano-bio-info” technology for in vivo test, single molecular detection and on-line medical diagnosis. Finally, future pros-pects to the fiber-optic DNA biosensors are predicted.
Keywords: DNA Hybridization; Fiber-Optic Biosen-sors; Label-Free; Nanotechnology
1. INTRODUCTION
Fiber-optic DNA biosensors are a kind of analytic setups, which convert the Waston-Crick base pairs matching duplex or Hoogsteen’s triplex (T/A-T or C/G-C) forma-tion into a readable analytical signals when functional-ized single-strands DNA (ssDNA) or double-strands DNA (dsDNA) [1,2] of interest are immobilized on the surface of side or end of fiber-optic hybrids with target DNA or interacts with ligands, for example pollutants [3] in the solution. This review will provide the information about the application and potential of fiber-optic DNA biosensors classified into two categories depending on the fiber with or without labels—label-free fiber-optic DNA biosensors and labeled fiber-optic DNA biosensor in recent years. With the development of nanotechnology, fiber-optic DNA biosensors have got great progresses because fiber-optic can be easily miniatured to the nanometer scale size by chemical etching [4] or tube etching [5] and mechanically pulled with CO2 laser heating setup [6], they are immune to electromagnet [7], disposability [8] and long-distance transmission [9]. Be-cause of these properties, fiber-optic DNA biosensors have increasingly attracted more attention to research and develop the new fiber-optic DNA biosensors that integrated with the “nano-bio-info” technology so that they can be employed for in vivo or within single cell test [10], especially in the intracellular measurement for real-time or on-line medical diagnosis [11,12]. On the basis of optical techniques that correlate changes in concentration, mass, number of molecules, or other properties to direct changes in the characteristics of light for detection of DNA hybridization or damage [13], dif-ferent label-free fiber-optic DNA biosensors are depicted in details. Finally, future prospects to fiber-optic DNA biosensors are brought forward.
2. ADVANTAGES AND DISADVANTAGES OF FIBER-OPTIC DNA BIOSENSORS
Nanoparticles [14,15], nanotubes [16,17], nanowires [17,18,19,20,21,22,23] and fiber-optics as the matrices of DNA biosensors to detect DNA specific sequence and DNA hybridization have been reported. Fiber optic- based DNA biosensors have many advantages over other matrices-based DNA biosensors as following:
1) Fibers have a flexible geometry and can be tracta-bly miniaturized at low cost to nanosacle structure for in vivo measurements.
2) Fibers are immune to electromagnet, lower tem-perature-dependence and low loss over long distance transmission


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