Browsing by Author "Lee, Mon-Juan"

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Bovine serum albumin detection and quantitation based on capacitance measurements of liquid crystals
(2016-08-29)
Lin, Chi-Hao
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Lee, Mon-Juan
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Lee, Wei
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影像與生醫光電研究所
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Institute of Imaging and Biomedical Photonics
Liquid crystal (LC)-based biosensing is generally limited by the lack of accurate quantitative strategies. This study exploits the unique electric capacitance properties of LCs to establish quantitative assay methods for bovine serum albumin (BSA) biomolecules. By measuring the voltage-dependent electric capacitance of LCs under an alternating-current field with increasing amplitude, positive correlations were derived between the BSA concentration and the electric capacitance parameters of LCs. This study demonstrates that quantitative analysis can be achieved in LC-based biosensing through electric capacitance measurements extensively employed in LCD research and development. Published by AIP Publishing.
Chiral liquid crystals as biosensing platforms
(2016-01-01)
Lee, Mon-Juan
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Sung, Yu-Chien
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Hsiao, Yu-Cheng
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Lee, Wei
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影像與生醫光電研究所
The texture observation has long been the core technique in liquid crystal (LC)-based bioassays. Its working principle stems from the dark-to-bright texture change induced by the interruption of the initially homeotropic alignment in nematic bulks or from the radial-to-bipolar configuration transition in LC droplets in the presence of biomolecules. One of the drawbacks of this observational scheme, which requires a polarizing optical microscope, is the difficulty in quantitative analysis. In this invited paper, we report on our recent development of alternative optical biosensing techniques based on cholesteric LCs (CLCs) without the use of a polarizer. The increase in structural order in a vertically anchored CLC cell in the quasi-planar state provides a means to allow detection and quantification of the concentration of biomolecules immobilized on the interface between the mesophase and the surfactant DMOAP for LC vertical alignment.
Dye- and dye-doped liquid crystals in biosensing
(2018-01-01)
Lee, Mon-Juan
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Chiang, Yi-Lun
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Karn, Abhishek
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Wu, Po-Chang
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Lee, Wei
Liquid crystals (LCs) have been suggested to have a place in biological sensing for detection and quantitation of biomolecules. Through many years, texture observation has long been the core technique in LC-based bioassays. Its principle stems from the texture change of LCs due to the interruption of the initially homeotropic alignment in nematic bulks or the radial-to-bipolar configuration transition in LC droplets in the presence of biomolecules. Biodetection through optical texture observation is convenient but remains a qualitative method, and alternative approaches of detection and quantitative analysis are necessary for the development of a practical LC-based biosensor. In this study, we explore the potential of two dye-enhanced LCs, a dye LC (DLC) and a dye-doped LC (DDLC), in biosensing and protein quantitation. Depending on the chromophore or dye incorporated in DLC and DDLC, the dichroic features of these LCs enable us to analyze the change in their orientation in the presence of biomolecules by transmission spectrometry, from which spectral parameters are derived to establish novel LC-based protein quantitative methods.
Dye-liquid-crystal-based biosensing for quantitative protein assay
(2018-03-01)
Wu, Po-Chang
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Karn, Abhishek
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Lee, Mon-Juan
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Lee, Wei
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Chen, Chao-Yuan
Dye liquid crystals (DLCs) have been extensively investigated in the field of liquid crystal display, but their potential in biosensing has not been explored. To provide insights into the potential of DLCs as a means of biosensing material, a DLC-based biosensor was developed for protein detection and quantitation. Unlike dye doped LCs, the DLC used in this study contains an azobenzene LC molecule chemically modified with two azo groups as chromophores, enabling the DLC to exhibit unique optical anisotropy and dichroic absorption at 470 rim, which were exploited in the quantitation of bovine serum albumin (BSA). The change in orientation of DLC molecules from the homeotropic to a disrupted state by BSA immobilized on the aligning-layer surface was evaluated in terms of the relative loss in transmittance, expressed by the standard parameter S%, due to the absorption as well as scattering of light. The DLC-based protein assay was capable of determining the BSA concentration, with which S% varied linearly between 1 mu g/ml and 7.5 mu g/ml. When the DLC molecules were reoriented from a BSA-disrupted state to the homeotropic alignment by an externally applied electric field, a linear correlation between S% and BSA concentration could be also derived from the voltage transmittance plots. The unique electro-optical properties of the intrinsically dichroic DLC are promising toward the development of a simple and reliable sensing platform for the quantitative analysis of biomolecules.
Electric-field-assisted signal amplification for label-free liquid-crystal-based detection of biomolecules
(2019-10-01)
Hsu, Wei-Liang
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Lee, Mon-Juan
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Lee, Wei
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影像與生醫光電研究所
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Institute of Imaging and Biomedical Photonics
The fundamental principle of liquid-crystal (LC)-based biosensing is the sensitive response of LC orientation to external stimuli. Biomolecules such as proteins or DNAs immobilized on the glass substrate of a LC cell are detected through disrupting the LC alignment and, in turn, altering the birefringence, resulting in changes in the optical texture that can be readily observed under a polarizing optical microscope. With an additional weak electric field across a sandwiched LC cell, we demonstrate in this study a novel label-free biodetection technique with amplified signal and improved detection limit. By applying the binarization analysis as the quantitative approach, the increase in the light leakage area in the optical texture of LCs with increasing amount of biomolecules can be quantitated with a bright-area-ratio (BAR)-versus-concentration curve. The reported biosensing technique exploits both the optical and electrical properties of LCs and is potentially applicable to other LC-based rapid screening and bioassays. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
Enhancing detection sensitivity in quantitative protein detection based on dye-doped liquid crystals
(2018-10-01)
Chiang, Yi-Lun
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Lee, Mon-Juan
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Lee, Wei
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光電學院
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College of Photonics
A quantitative protein assay and label-free immunodetection based on dye-doped liquid crystal (DDLC) was developed in this study. The black dye incorporated as the dopant in the DDLC mixture features a high dichroic ratio and wide visible-light absorption band so that the level of disturbance in DDLC orientation in the presence of biomolecules can be readily observed with the naked eye. Due to the absorption and anisotropic features of DDLC, transmission spectrometry was exploited to establish a quantitative method for DDLC-based biosensing. Our results indicate that the transmittance of DDLC decreased with increasing concentration of bovine serum albumin (BSA), a common protein standard, and the detection sensitivity can be improved by using linearly polarized light during spectral measurement. A linear correlation between the spectral parameters of DDLC and BSA concentration was thus derived to facilitate protein quantitation. As a demonstration of clinical relevance, a label-free DDLC-based immunoassay for the cancer biomarker CA125 was manifested by reacting CA125 with immobilized anti-CA125 antibody. The transmittance of DDLC decreased with increasing concentration of CA125, but when a nonspecific protein such as BSA was reacted with the anti-CA125 antibody, the transmission spectrum was similar to that in the absence of CA125, suggesting that immunodetection via the DDLC-based biosensing platform was specific. It is evident from this study that with its unique dichroic and optical properties, DDLC is a potential biosensing material with capabilities of both qualitative detection as required in rapid screening as well as quantitative bioassay as in cancer screening.
Highly sensitive color-indicating and quantitative biosensor based on cholesteric liquid crystal
(2015-12-01)
Hsiao, Yu-Cheng
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Sung, Yu-Chien
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Lee, Mon-Juan
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Lee, Wei
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影像與生醫光電研究所
Liquid crystal (LC)-based biosensors employ highly sensitive interfaces between the alignment layers and LCs to detect biomolecules and their interactions. Present techniques based on optical texture observation of the homeotropic-to-planar response of nematic LCs are limited by their quantitative reproducibility of results, indicating that both the accuracy and reliability of LC-based detection require further improvements. Here we show that cholesteric LC (CLC) can be used as a novel sensing element in the design of an alternative LC-based biosensing device. The chirality of the vertically anchored (VA) CLC was exploited in the detection of bovine serum albumin (BSA), a protein standard commonly used in protein quantitation. The color appearance and the corresponding transmission spectrum of the cholesteric phase changed with the concentration of BSA, by which a detection limit of 1 fg/ml was observed. The optical response of the VA CLC interface offers a simple and inexpensive platform for highly sensitive and naked-eye color-indicating detection of biomolecules, and, thus, may facilitate the development of point-of-care devices for the detection of disease-related biomarkers. (C) 2015 Optical Society of America
Immunoassays for the cancer biomarker CA125 based on a large-birefringence nematic liquid-crystal mixture
(2015-01-01)
Sun, Shih-Hung
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Lee, Mon-Juan
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Lee, Yun-Han
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Lee, Wei
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Song, Xiaolong
The use of fluorescence is ubiquitously found in the detection of immunoreaction; though with good sensitivity, this technique requires labeling as well as other time-consuming steps to perform the measurement. An alternative approach involving liquid crystals (LCs) was proposed, based on the fact that an immunocomplex can disturb the orientation of LCs, leading to an optical texture different from the case when only antigen or antibody exists. This method is label-free, easy to manipulate and lowcost. However, its sensitivity was low for practical usage. In this study, we adopted a high-birefringence liquid crystal (LC) to enhance the sensitivity for the immunodetection. Experiments were performed, targeting at the cancer biomarker CA125. We showed that the larger birefringence (Delta n = 0.33 at 20 degrees C) amplifies the detected signal and, in turn, dramatically improves the detection limit. To avoid signal loss from conventional rinsing steps in immunodetection, CA125 antigen and antibody were reacted before immobilized on substrates. We studied the specific binding events and obtained a detection limit as low as 1 ng/ml. The valid temperature ranges were compared by using the typical single-compound LC 5CB and the high-birefringence LC mixture. We further investigated time dependency of the optical textures and affirmed the capability of LC-based immunodetection in distinguishing between specific and nonspecific antibodies.
Label-free immunodetection of the cancer biomarker CA125 using high-Delta n liquid crystals
(2014-07-01)
Su, Hui-Wen
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Lee, Yun-Han
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Lee, Mon-Juan
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Hsu, Yi-Chiang
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Lee, Wei
A label-free and array-based optical liquid-crystal (LC) immunodetection technique for the detection of CA125 antigen, a protein biomarker most frequently used for ovarian cancer detection, was demonstrated with a nematic LC with larger birefringence (Delta n) to promote sensitivity in detecting biomolecules. The LC-based immunodetection offers an alternative and sensitive approach for the detection of biomarker proteins, with the potential of replacing conventional immunoassays used in biochemical studies and clinical laboratories. (C) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License.
Label-free protein quantitation by dielectric spectroscopy of dual-frequency liquid crystal
(2019-03-01)
Lin, Ching-Min
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Wu, Po-Chang
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Lee, Mon-Juan
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Lee, Wei
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光電學院
A dual-frequency-liquid-crystal (DFLC)-based biosensor was developed and its frequency-dependent dielectric properties were exploited to detect and quantitate a protein standard, bovine serum albumin (BSA). By analyzing the dielectric spectra of DFLC in the presence of BSA at various concentrations, we found that the difference in dielectric permittivity between the high- and low-frequency regimes is correlated to BSA concentration, thereby permitting a DFLC-based protein quantitative method. The dielectric properties of DFLCs are fundamental in the design of liquid crystal displays and fast-switching devices. Results from this study demonstrate the extended potential of the frequency-revertible dielectric anisotropy of DFLC in biosensing and protein quantitation.
Label-free protein sensing by employing blue phase liquid crystal
(2017-03-01)
Lee, Mon-Juan
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Chang, Chung-Huan
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Lee, Wei
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光電學院
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College of Photonics
Blue phases (BPs) are mesophases existing between the isotropic and chiral nematic phases of liquid crystals (LCs). In recent years, blue phase LCs (BPLCs) have been extensively studied in the field of LC science and display technology. However, the application of BPLCs in biosensing has not been explored. In this study, a BPLC- based biosensing technology was developed for the detection and quantitation of bovine serum albumin (BSA). The sensing platform was constructed by assembling an empty cell with two glass slides coated with homeotropic alignment layers and with immobilized BSA atop. The LC cells were heated to isotropic phase and then allowed to cool down to and maintained at distinct BP temperatures for spectral measurements and texture observations. At BSA concentrations below 10(- 6) g/ ml, we observed that the Bragg reflection wavelength blueshifted with increasing concentration of BSA, suggesting that the BP is a potentially sensitive medium in the detection and quantitation of biomolecules. By using the BPLC at 37 degrees C and the same polymorphic material in the smectic A phase at 20 degrees C, two linear correlations were established for logarithmic BSA concentrations ranging from 10(- 9) to 10(- 6) g/ ml and from 10(- 6) to 10(- 3) g/ ml. Our results demonstrate the potential of BPLCs in biosensing and quantitative analysis of biomolecules. (C) 2017 Optical Society of America
Liquid crystal-based capacitive, electro-optical and dielectric biosensors for protein quantitation
(1970-01-01)
Lee, Mon-Juan
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Lee, Wei
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光電學院
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College of Photonics
The electrical, electro-optical and dielectric properties of liquid crystals (LCs) are routinely manipulated in liquid-crystal display (LCD) devices, but their potential application in the development of biosensors is still in a nascent stage. In this review, utilising the electrical properties, electro-optical effect and dielectric anisotropy in LCs, we provide insights into several possible modes of label-free biodetection and describe how capacitance, electro-optical and dielectric measurements of various LCs assist in quantitative analysis of biomolecules. It is concluded that the electrically induced biosensing techniques proposed here provides new incentives for researchers to study the interaction between LCs and biomolecules and to resolve technical hurdles facing the development of LC-based biosensors.
Liquid crystal-based capacitive, electro-optical and dielectric biosensors for protein quantitation
(2020-06-20)
Lee, Mon-Juan
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Lee, Wei
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光電學院
;
College of Photonics
The electrical, electro-optical and dielectric properties of liquid crystals (LCs) are routinely manipulated in liquid-crystal display (LCD) devices, but their potential application in the development of biosensors is still in a nascent stage. In this review, utilising the electrical properties, electro-optical effect and dielectric anisotropy in LCs, we provide insights into several possible modes of label-free biodetection and describe how capacitance, electro-optical and dielectric measurements of various LCs assist in quantitative analysis of biomolecules. It is concluded that the electrically induced biosensing techniques proposed here provides new incentives for researchers to study the interaction between LCs and biomolecules and to resolve technical hurdles facing the development of LC-based biosensors.
Liquid-crystal-based biosensing beyond texture observations
(2015-01-01)
Lee, Mon-Juan
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Lin, Chi-Hao
;
Lee, Wei
;
光電學院
;
College of Photonics
The texture observation has long been the core technique in liquid crystal (LC)-based biosensing. One of the drawbacks of this observational means is the difficulty in quantitative analysis. In this invited paper, we report on our recent attempt to improve the LC-based biosensing technique through the analysis of bovine serum albumin (BSA), a protein standard commonly used in the assay of protein concentration. We propose to overcome the technical limitations in the analysis of LC-based biosensors by considering alternative measuring schemes. By means of the induced changes in electro-optical properties of LCs in the presence of different concentrations of BSA, novel quantitative techniques specific for LC-based biosensors are developed.
Surface modification of alignment layer by ultraviolet irradiation to dramatically improve the detection limit of liquid-crystal- based immunoassay for the cancer biomarker CA125
(2015-05-01)
Su, Hui-Wen
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Lee, Mon-Juan
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Lee, Wei
;
影像與生醫光電研究所
;
Institute of Imaging and Biomedical Photonics
Liquid crystal (LC)-based biosensing has attracted much attention in recent years. We focus on improving the detection limit of LC-based immunoassay techniques by surface modification of the surfactant alignment layer consisting of dimethyloctadecyl[3-(trimethoxysilyl) propyl] ammonium chloride (DMOAP). The cancer biomarker CA125 was detected with an array of anti-CA125 antibodies immobilized on the ultraviolet (UV)-modified DMOAP monolayer. Compared with a pristine counterpart, UV irradiation enhanced the binding affinity of the CA125 antibody and reproducibility of immunodetection in which a detection limit of 0.01 ng/ml for the cancer biomarker CA125 was achieved. Additionally, the optical texture observed under a crossed polarized microscope was correlated with the analyte concentration. In a proof-of-concept experiment using CA125spiked human serum as the analyte, specific binding between the CA125 antigen and the anti-CA125 antibody resulted in a distinct and concentration-dependent optical response despite the high background caused by nonspecific binding of other biomolecules in the human serum. Results from this study indicate that UV modification of the alignment layer, as well as detection with LCs of large birefringence, contributes to the enhanced performance of the label-free LC-based immunodetection, which may be considered a promising alternative to conventional label-based methods. (C) 2015 Society of Photo-Optical Instrumentation Engineers (SPIE)