Using liquid crystals to detect DNA hybridization on polymeric surfaces with continuous wavy features.
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.
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ABSTRACT: In this study, we report a new method for the high contrast imaging of biomolecular interactions at roller printed protein surfaces using thermotropic liquid crystals (LCs). Avidin was roller printed and covalently immobilized onto the obliquely deposited gold surface that was decorated with carboxylic acid-terminated self-assembled monolayers (SAMs). The optical response of LCs on the roller printed film of avidin contrasted sharply with that on the obliquely deposited gold surface. The binding of biotin-peroxidase to the roller printed avidin was then investigated on the obliquely deposited gold substrate. LCs exhibited a non-uniform and random orientation on the roller printed area decorated with the complex of avidin and biotin-peroxidase, while LCs displayed a uniform and planar orientation on the area without roller printed proteins. The orientational transition of LCs from uniform to non-uniform state was triggered by the erasion of nanometer-scale topographies on the roller printed surface after the binding of biotin-peroxidase to the surface-immobilized avidin. The specific binding events of protein-receptor interactions were also confirmed by atomic force microscopy and ellipsometry. These results demonstrate that the roller printing of proteins on obliquely deposited gold substrates could provide a high contrast signal for imaging biomolecular interactions using LC-based sensors.Bulletin- Korean Chemical Society 10/2012; 33(10). DOI:10.5012/bkcs.2012.33.10.3269 · 0.84 Impact Factor
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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. DOI:10.1016/j.colsurfb.2013.12.037 · 4.29 Impact Factor
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ABSTRACT: In this study, we demonstrate the detection of mRNA from Escherichia coli in drinking water using thermotropic liquid crystals (LCs). After hybridization of complementary mRNA with the single-stranded DNA immobilized on a polymer substrate containing periodic sinusoidal wave patterns, the orientation of LCs transits from a uniform to a non-uniform state, thereby inducing a change in the optical response of LCs. The periodic sinusoidal features of the polymer substrate are obtained through buckling the poly-(dimethylsiloxane) slide on a cylindrical surface, followed by replicating the associated relief structures on a poly-(urethaneacrylate) surface, where a film of gold was deposited. Then, thiol-modified single-stranded DNA was functionalized on the gold film as an mRNA receptor. The formation of mRNA–single-stranded DNA complex, which covers the sinusoidal nanostructures on the surface, induces the orientational transition of LCs. This result indicates that LCs can be used to report the specific hybridization of mRNA with single-stranded DNA, which holds promise for the sensitive and label-free detection of viable bacterial pathogens in drinking water.Colloid and Polymer Science 05/2014; 292(5):1163-1169. DOI:10.1007/s00396-014-3162-7 · 2.41 Impact Factor