title: Immunoassays for the cancer biomarker CA125 based on a large-birefringence nematic liquid-crystal mixture.
abstract: 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 low-cost. 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 (Δn = 0.33 at 20 °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.
authors: Institute of Imaging and Biomedical Photonics, College of Photonics, National Chiao Tung University, Guiren Dist., Tainan 71150, Taiwan.
authors: Shih-Hung
authors: SH
authors: Sun
authors: Department of Bioscience Technology, Chang Jung Christian University, Guiren Dist., Tainan 71101, Taiwan ; mjlee@mail.cjcu.edu.tw (M.-J. Lee).
authors: Mon-Juan
authors: MJ
authors: Lee
authors: Institute of Imaging and Biomedical Photonics, College of Photonics, National Chiao Tung University, Guiren Dist., Tainan 71150, Taiwan.
authors: Yun-Han
authors: YH
authors: Lee
authors: Institute of Imaging and Biomedical Photonics, College of Photonics, National Chiao Tung University, Guiren Dist., Tainan 71150, Taiwan.
authors: Wei
authors: W
authors: Lee
authors: Jiangsu Hecheng Display Technology Co., Ltd., Nanjing 210014, China.
authors: Xiaolong
authors: X
authors: Song
authors: Jiangsu Hecheng Display Technology Co., Ltd., Nanjing 210014, China.
authors: Chao-Yuan
authors: CY
authors: Chen
keywords: (160.3710) Liquid crystals; (170.0170) Medical optics and biotechnology
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