Electrokinetic concentration on a microfluidic chip using polyelectrolytic gel plugs for small molecule immunoassay

• Published in: Electrochimica acta Vol. 110; pp. 164 - 171
• Main Authors: Han, Donghoon, Kim, Kwang Bok, Kim, Yang-Rae, Kim, Solji, Kim, Hee Chan, Lee, Junghwa, Kim, Joohoon, Chung, Taek Dong
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.11.2013
• Subjects: Biotin; Channels; Chips; Displacement; Electrokinetic preconcentration; Electrokinetics; Immunoassay; Indicators; Microfluidic device; Microfluidics; Polyelectrolytic gel plug; Small molecule immunoassay; Electrokinetic preconcentration; Small molecule immunoassay; Polyelectrolytic gel plug; Microfluidic device
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2013.02.005

We have devised a new method to enhance the sensitivity of competitive immunoassay using electrokinetic concentration near a pair of highly charge-selective polymer [poly-2-acrylamido-2-methyl-1-propanesulfonic acid (pAMPSA)] plugs on a microfluidic chip. The polyelectrolytic gel, which was photopolymerized in a microfluidic channel network, served as the effective charge-selective extractor to sophisticatedly control the ion distribution. In this system, the fluorescent indicators on magnetic microbeads dispersed in the sample were spontaneously displaced by unlabeled target molecules and then electrokinetically preconcentrated in a single spot on the microfluidic chip. The locally preconcentrated fluorescent indicators were detected by laser-induced fluorescence. As a proof-of-concept, the competitive displacement assay of unlabeled 1nM biotin was conducted to observe ca. 2000-fold enrichment within 3min. In addition to the sensitive assessment of the unlabeled small target molecules, the proposed immunoassay system also showed good selectivity for biotin analogs such as biocytin, 2-iminobiotin, desthiobiotin.