Microgap Structured Optical Sensor for Fast Label-free DNA Detection

• Main Author: Wang, Yunmiao
• Other Authors: Electrical and Computer Engineering
• Format: Others
• Published: Virginia Tech 2014
• Subjects: Fiber Optic Biosensor; DNA Sequence Identification; Fabry-Perot Interferometer; Microprobe
• Online Access: http://hdl.handle.net/10919/32875; http://scholar.lib.vt.edu/theses/available/etd-05162011-135450/

DNA detection technology has developed rapidly due to its extensive application in clinical diagnostics, bioengineering, environmental monitoring, and food science areas. Currently developed methods such as surface Plasmon resonance (SPR) methods, fluorescent dye labeled methods and electrochemical methods, usually have the problems of bulky size, high equipment cost and time-consuming algorithms, so limiting their application for in vivo detection. In this work, an intrinsic Fabry-Perot interferometric (IFPI) based DNA sensor is presented with the intrinsic advantages of small size, low cost and corrosion-tolerance. This sensor has experimentally demonstrated its high sensitivity and selectivity. In theory, DNA detection is realized by interrogating the sensorâ s optical cavity length variation resulting from hybridization event. First, a microgap structure based IFPI sensor is fabricated with simple etching and splicing technology. Subsequently, considering the sugar phosphate backbone of DNA, layer-by-layer electrostatic self-assembly technique is adopted to attach the single strand capture DNA to the sensor endface. When the target DNA strand binds to the single-stranded DNA successfully, the optical cavity length of sensor will be increased. Finally, by demodulating the sensor spectrum, DNA hybridization event can be judged qualitatively. This sensor can realize DNA detection without attached label, which save the experiment expense and time. Also the hybridization detection is finished within a few minutes. This quick response feature makes it more attractive in diagnose application. Since the sensitivity and specificity are the most widely used statistics to describe a diagnostic test, so these characteristics are used to evaluate this biosensor. Experimental results demonstrate that this sensor has a sensitivity of 6nmol/ml and can identify a 2 bp mismatch. Since this sensor is optical fiber based, it has robust structure and small size ( 125μm ). If extra etching process is applied to the sensor, the size can be further reduced. This promises the sensor potential application of in-cell detection. Further investigation can be focused on the nanofabrication of this DNA sensor, and this is very meaningful topic not only for diagnostic test but also in many other applications such as food industry, environment monitoring. === Master of Science