title: Microfluidic immunoassay with plug-in liquid crystal for optical detection of antibody.
abstract: Recent advance in liquid crystal (LqC) based immunoassays enables label-free detection of antibody, but manual preparation of LqC cells and injection of LqC are required. In this work, we developed a new format of LqC-based immunoassay which is hosted in a microfluidic device. In this format, the orientations of LqC are strongly influenced by four channel walls surrounding the LqC. When the aspect ratio (depth/width) of the channel is smaller than 0.38, LqC orients homeotropically inside the microchannel and appears dark. After antigens bind to immobilized antibodies on the channel walls, a shift of the LqC appearance from dark to bright (due to the disruption of LqC orientation) can be visualized directly. To streamline the immunoassay process, a tubing cartridge loaded with a sample solution, washing buffers and a plug of LqC is connected to the microfluidic device. By using pressure-driven flow, the cartridge allows antigen/antibody binding, washing and optical detection to be accomplished in a sequential order. We demonstrate that this microfluidic immunoassay is able to detect anti-rabbit IgG with a naked-eye detection limit down to 1 μg mL(-1). This new format of immunoassay provides a simple and robust approach to perform LqC-based label-free immunodetection in microfluidic devices.
authors.affiliation: Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, 117585, Singapore.
authors.forename: Qingdi
authors.initials: Q
authors.lastname: Zhu
authors.affiliation: Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, 117585, Singapore. Electronic address: cheyk@nus.edu.sg.
authors.forename: Kun-Lin
authors.initials: KL
authors.lastname: Yang
mesh_terms: D000818:Animals; D000906:Antibodies / Q000032:analysis*; D000888:Antibodies, Anti-Idiotypic / Q000032:analysis; D055910:Antibodies, Immobilized / Q000032:analysis; D000937:Antigen-Antibody Reactions; D007118:Immunoassay / Q000295:instrumentation / Q000379:methods*; D007074:Immunoglobulin G / Q000032:analysis; D050866:Liquid Crystals / Q000737:chemistry*; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation; D011817:Rabbits
chemical_list: D000906:Antibodies; D000888:Antibodies, Anti-Idiotypic; D055910:Antibodies, Immobilized; D007074:Immunoglobulin G; C048844:anti-IgG
keywords: Immunoassay; Label-free assay; Liquid crystal detection; Microfluidics; One-step assay