Abstract
Biosensors based on liquid crystal (LC) materials can be made by employing the sensitive interfacial effect between LC molecules and alignment layers on substrates. In the past, the optical texture observation method was used in the LC biosensor field. However, the method is limited by a complicated fabrication process and quantitative reproducibility of results that bv evidence that both the reliability and accuracy of LC biosensors need to be improved. In this report, we demonstrate that cholesteric LC (CLC) cells in which one substrate is coated with a vertically aligned layer can be used as a new sensing technology. The chirality of the single vertically anchored (SVA)/CLC biosensor was tested by detecting bovine serum albumin (BSA), a protein standard commonly used in the lab. The colors and corresponding spectrum of the SVA/CLC biosensor changed with the BSA concentrations. A detection limit of 1 ng/ml was observed for the SVA/CLC biosensor. The linear optical properties of the SVA/CLC biosensor produced cheap, inexpensive, and color-indicating detection of biomolecules, and may promote the technology of point-of-care devices for disease-related biomarker detection.
Highlights
The use of a nematic liquid crystal (LC) to detect biomolecules was first proposed by Abbott’s group [1]
Because the light scattering caused by the random cholesteric LC (CLC) structure was much stronger at lower bovine serum albumin (BSA) concentrations and the number of defect lines in the optical textures were reduced when the BSA concentration increased, the content of the random focal conic (FC) state was higher in the non-biomolecule situation
The chirality of the vertically aligned CLC molecules was sensitive to the amount BSA on the alignment layer
Summary
The use of a nematic liquid crystal (LC) to detect biomolecules was first proposed by Abbott’s group [1]. Based on the properties of CLCs, many applications have been proposed, such as tunable photonic crystal devices [13,14,15], displays [16], and optic devices [17,18] Despite their photonic applications, the potential of CLCs as biosensors have rarely been investigated. The vertical anchoring strength of CLC molecules is weakened when the biomolecules are adsorbed onto DMOAP-coated substrates. These biomolecules allow CLC molecules to transfer to the P structure on the DMOAP-coated side which causes the device to be in the major transmission mode. The transition of the CLC structure from major reflection to major transmission mode brings about the color-indicating properties of SVA/CLC. Quantitation of the concentrations of BSA with a lower detection limit of ∼1 ng/ml can be realized by measuring the SVA/CLC biosensor using transmission spectroscopy
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