Using liquid crystals to detect DNA hybridization on polymeric surfaces with continuous wavy features.

College of BioNano Technology, Kyungwon University,Sujeong-Gu, Seongnam-City, Gyeonggi-Do, Korea.
Nanotechnology (Impact Factor: 3.84). 10/2010; 21(42):425502. DOI: 10.1088/0957-4484/21/42/425502
Source: PubMed

ABSTRACT In this study, we examined the orientational behavior of thermotropic liquid crystals (LCs) supported on a film of DNA that was chemically immobilized on a nanostructure surface. The surface was comprised of gold film deposited onto a polymer substrate that had a sinusoidal distortion normal to the surface, leading to a parallel array of peaks and troughs. The sinusoidal structures were produced by treating a polydimethylsiloxane (PDMS) substrate with oxygen plasma and buckled on a cylindrical surface. This patterned PDMS was then used to create replicas of the associated relief structures on another polymer surface, poly(urethaneacrylate), where a film of gold was deposited. The gold films were functionalized with thiol-modified DNA, and then used as substrates for the hybridization of a complementary strand of DNA (cDNA). The orientation of nematic 4-cyano-4'-pentylbiphenyl (5CB) was found to be parallel to the plane of the surface-immobilized DNA before incubation with a solution of cDNA. However, the hybridization of DNA induced a random orientation of 5CB, indicating that the DNA complexes disturbed the sinusoidal structure of the surface. These results demonstrate that LC can be used to detect the hybridization of DNA by manipulating the response of LC to the DNA decorated surfaces.

  • [Show abstract] [Hide abstract]
    ABSTRACT: In this study, we demonstrated a label-free detection of viruses using liquid crystals (LCs) on a polymeric surface with periodic nanostructures. The polymeric nanostructures, which hold sinusoidal anisotropic patterns, were created by a sequential process of poly-(dimethylsiloxane) buckling and replication of the patterns on a poly-(urethane acrylate) surface containing a film of gold. After immobilization of human cytomegalovirus- and adenovirus-antibodies onto the polymeric surface treated with a mixed self-assembled monolayer, a uniform appearance reflecting the uniform orientation of 4-cyano-4'-pentylbiphenyl (5CB) was observed. Conversely, binding of viruses to their antibody decorated surface induced a random appearance of 5CB from the random orientation of 5CB. The uniform to random orientational transition of 5CB indicates that the anisotropic topography of the polymeric surface was masked after specific binding of viruses to the antibody decorated surface. We evaluated the specificity of the binding events by confirming topographical changes and optical thickness using atomic force microscopy and ellipsometry, respectively. These results demonstrate that polymeric surfaces with continuous anisotropic patterns can be used to amplify the presence of nanoscopic virions into an optical response of LC, as well as expand the scope of LC-based biological detection on polymeric solid surfaces.
    Colloids and surfaces B: Biointerfaces 01/2014; 116C:147-152. · 4.28 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this study, we report spontaneous formation of two characteristic micrometer-scale liquid crystal (LC) droplet patterns on solid surfaces and also demonstrate the application of the designed LC platform to construct new types of LC-based sensors. By simply spreading LCs dissolved in organic solvents on glass microscope slides, we observed one- and two-dimensional LC droplet patterns with distinctive optical textures that represent different orientations of LCs under a polarized microscope. LC droplets supported on surfaces exhibited high stability during temperature-induced phase transitions of LCs. In addition, based on the distinguishable optical appearance of the LC droplet patterns, their applications in monitoring the presence of water vapors, amphiphiles, and vapors of volatile organic compounds (VOCs) were demonstrated. These results indicate that the surface-anchored LC droplets show high promise for the development of simple, robust, and versatile LC pattern-based sensing devices for real-time and label-free detection of chemical and biological events.
    Soft Matter 05/2013; 9(24):5779-5784. · 4.15 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In this study, we developed a liquid crystal (LC)-based detection method for polymer films synthesized on solid surfaces. A dark to bright transition in the optical appearance of nematic 4-cyano-4′-pentylbiphenyl (5CB) was observed after transferring a poly(methyl methacrylate) (PMMA) film onto a glass substrate functionalized with n-octyltrichlorosilane (OTS). This phenomenon indicates an orientational transition of 5CB from a homeotropic to a planar-random state. The optical response of 5CB was then evaluated directly through polymerization reactions on the OTS-functionalized glass substrate. Polymer films of PMMA, poly(glycidyl methacrylate) (PGMA), and poly(dimethylsiloxane) (PDMS) were synthesized on OTS surfaces covered with their reaction mixtures. All polymer films displayed bright signals of 5CB, which corresponded to the planar-random orientation of LCs. However, no change in orientation was observed for the control experiments. We confirmed the formation of polymer films on the OTS surface using atomic force microscopy. Overall, our results suggest that LCs can be used to construct optical monitoring systems for the product of polymerization reactions. Figure ᅟ
    Colloid and Polymer Science 11/2013; · 2.16 Impact Factor