Simple Detection of Binding Events Using an Anchoring Transition of Liquid Crystals on the Immobilized oligoDNAs
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Simple Detection of Binding Events Using an Anchoring Transition of Liquid Crystals on the Immobilized oligoDNAs Hak-Rin Kim1, Min-Geon Choi1, Joo-Eun Kim1, Eui-Yul Choi2,3, Sang-Wook Oh4, and JaeHoon Kim1 1 Department of Electronics and Computer Engineering, Hanyang University, 17 HaengdangDong, Seongdong-Gu, Seoul, 133-791, Korea, Republic of 2 Central Research Institute of Boditech Inc., Chunchon, Kangwon-Do, 200-160, Korea, Republic of 3 Department of Genetic Engineering, Hallym University, Chunchon, Kangwon-Do, 200-702, Korea, Republic of 4 Department of Biology Education, Chonbuk National University, Jeonju, Jeonbuk, 561-756, Korea, Republic of
ABSTRACT We propose a novel method for optically detecting hybridization results in a deoxyribonucleic acid (DNA) chip using an anchoring transition of a nematic liquid crystal (NLC). Since the LC anchoring condition highly depends on variation of the surface morphology, DNA hybridization result induces an anchoring transition of NLCs from a homeotropic orientation to a random planar orientation. It is demonstrated that such hybridization results and the subsequent anchoring transition of LCs are detectable with simple optical instruments by utilizing large optical birefringence variation and propagation of the long-range orientational order in NLCs.
INTRODUCTION Biosensors detect biological events by recognizing specific biomolecular binding interactions in a bioreceptor part, convert biomolecular events into measurable signals in a transducer part, and analyze transformed signals in a signal processing part. As a transducer, most of biosensors adopt a fluorescent or a radioactive probing technique, which requires expensive and sophisticated measurement systems and complicated analysis tools [1]. Recently, it has been reported that delicate biological surface binding effects can be optically measured by using a surface-dependent liquid crystal (LC) anchoring behavior and its long-range orientational order propagation [2-4]. In such systems, the interface between the LC molecules and the biological surface acts as a transducer part of the biosensor. Therefore, understating the interplay between the LC molecules and the biologically modified surface at the interface is very important to construct a cost-effective and simple biosensor system. In this work, we propose a novel method for detecting hybridization results in a deoxyribonucleic acid (DNA) chip using an anchoring transition of LC alignment. It was found that an initial homeotropic LC orientation on a single-stranded DNA (ssDNA) surface was changed to a random-planar LC orientation on a double-stranded DNA (dsDNA) surface after
hybridization. Such hybridization results were effectively transformed into optical signals via the LC layer, which could be measured even by naked human eyes with only simple polarizing optical system.
PRINCIPLES OF OPERATION Figure 1 shows the schematic diagrams of our nematic LC (NLC)-based DNA chip structure and the NLC configurations depending on the hybridization re
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