Development of Tubing-based Stationary Liquid-phase Enzyme-linked Immunosorbent Assay
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Original Article
Development of Tubing-based Stationary Liquid-phase Enzyme-linked Immunosorbent Assay Soonil Kwon & Suk-Jung Choi
*
Received: 26 December, 2018 / Accepted: 03 March, 2019 / Published online: 23 April, 2019 ⒸThe Korean BioChip Society and Springer 2018
Abstract Although lab-on-a-chip is a promising platform for point-of-care-testing (POCT) applications, its commercialization has been hampered due to complex fabrication processes or the need for additional lab instruments. In this study, tubing-based colourimetric and volumetric enzyme-linked immunosorbent assay (ELISA) methods were developed for application in POCT of cortisol and Salmonella typhimurium, respectively. Different solutions required for each assay were contained in a piece of tubing, forming different aqueous layers that were separated by immiscible organic layers. The assay was carried out by moving antibody-functionalized, solid-phase magnetic particles through the layers with a hand-operated magnet. This method enabled detection of cortisol at a low detection limit of 0.1 ng/mL within 12 min and detection of S. typhimurium down to 102 cfu/sample within 1 h. The performance of the assay methods was comparable to or better than that of conventional ELISA despite the assay systems and methods being extremely simple, thus demonstrating its potential for POCT application. Keywords: Enzyme-linked immunosorbent assay, Stationary liquid phase, cortisol, Salmonella typhimurium, Magnetic particle
Department of Chemistry, Gangneung-Wonju National University, Gangneung 25457, Korea *Correspondence and requests for materials should be addressed to S.J. Choi ( [email protected])
Introduction Lab-on-a-chip (LOC) is a promising platform for point-of-care-testing (POCT) because of its ability to carry out laborious analyses such as enzyme-linked immunosorbent assays (ELISA) on a single chip1–4. However, many LOCs have complicated structures involving chambers, channels, and valves for storing different solutions for ELISA and require additional instruments for controlling the liquid flow, thus hampering commercialization5,6. It is therefore essential to simplify the LOC system while retaining its performance for POCT applications. Recently, stationary liquid-phase (SLP) LOC was suggested as a simple platform for immunoassays of toxins or pathogenic bacteria7–9. The SLP LOC consists of a linear array of two or three chambers connected by channels, and the assay process is carried out by moving solid phase magnetic particles through the chambers containing different solutions. The mechanical requirement for the assay process is the movement of a magnet and vibration of the LOC, which can be achieved by simple equipment consisting of a linear actuator and a vibrating motor. The SLP LOC allowed the detection of target analyte with a sensitivity comparable to that of conventional immunoassay methods despite the simple structure of the LOC and the operating instrument. However, the requirement of different solutions being separated using valves for
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