Abstract
A liquid-crystal (LC)-filled transmission electron microscopy (TEM) grid cell coated with the cationic surfactant dodecyltrimethylammonium bromide (DTAB), to which a single-stranded deoxyribonucleic acid probe (ssDNAprobe) was adsorbed at the LC/aqueous interface (TEMDTAB/DNA), was applied for the highly specific detection of target DNA molecules. The DTAB-coated E7 (used LC mixture) in the TEM grid (TEMDTAB) exhibited a homeotropic orientation, and changed to a planar orientation upon adsorption of the ssDNAprobe. The TEMDTAB/DNA was then exposed to complementary (target) ssDNA, which resulted in a planar-to-homeotropic configurational change of E7 that could be observed through a polarized optical microscope under crossed polarizers. The optimum adsorption density (2 μM) of ssDNAprobe enabled the detection of ≥0.05 nM complementary ssDNA. This TEMDTAB/DNA biosensor could differentiate complementary ssDNA from mismatched ssDNA as well as double-stranded DNA. It also successfully detected the genomic DNAs of the bacterium Erwinia carotovora and the fungi Rhazictonia solani. Owe to the high specificity, sensitivity, and label-free detection, this biosensor may broaden the applications of LC-based biosensors to pathogen detection.
Highlights
A liquid-crystal (LC)-filled transmission electron microscopy (TEM) grid cell coated with the cationic surfactant dodecyltrimethylammonium bromide (DTAB), to which a single-stranded deoxyribonucleic acid probe was adsorbed at the Liquid crystals (LCs)/aqueous interface (TEMDTAB/DNA), was applied for the highly specific detection of target DNA molecules
The TEMDTAB/DNA was exposed to complementary single-stranded DNA (ssDNA), which resulted in a planar-to-homeotropic configurational change of E7 that could be observed through a polarized optical microscope under crossed polarizers
The 8 mM solution of DTAB caused a clear homeotropic orientation of E7 at the LC/aqueous interface, and so the concentration of DTAB in water was fixed at 8 mM for all experiments, unless otherwise specified
Summary
A liquid-crystal (LC)-filled transmission electron microscopy (TEM) grid cell coated with the cationic surfactant dodecyltrimethylammonium bromide (DTAB), to which a single-stranded deoxyribonucleic acid probe (ssDNAprobe) was adsorbed at the LC/aqueous interface (TEMDTAB/DNA), was applied for the highly specific detection of target DNA molecules. As shown, the cationic surfactant dodecyltrimethylammonium bromide (DTAB) was adsorbed to form a self-assembled monolayer on the surface of an LC-filled TEM grid (TEMDTAB) This TEMDTAB grid cell was further functionalized with ssDNAprobe (TEMDTAB/DNA) by its electrostatic adsorption onto the DTAB monolayer for highly selective hybridization with ssDNAtarget, which could alter the LC anchoring as a result of the altered net charge density at the LC/aqueous interface. This LC-based biosensor can be used without the need for molecular labeling or sophisticated instruments, giving it a lot of potential for effective applications to the detection of DNA
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