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Micromachines 2019, 10(2), 107; https://doi.org/10.3390/mi10020107

Heterogeneous Immunoassay Using Channels and Droplets in a Digital Microfluidic Platform

1
Microbiome Program, Center for Individualized Medicine, Mayo Clinic, Rochester, MN 55905, USA
2
Department of Bioengineering, University of Illinois at Chicago, Chicago, IL 60607, USA
*
Author to whom correspondence should be addressed.
Received: 15 December 2018 / Revised: 29 January 2019 / Accepted: 1 February 2019 / Published: 5 February 2019
(This article belongs to the Special Issue 10th Anniversary of Micromachines)
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Abstract

This work presents a heterogeneous immunoassay using the integrated functionalities of a channel and droplets in a digital microfluidic (DMF) platform. Droplet functionality in DMF allows for the programmable manipulation of discrete sample and reagent droplets in the range of nanoliters. Pressure-driven channels become advantageous over droplets when sample must be washed, as the supernatant can be thoroughly removed in a convenient and rapid manner while the sample is immobilized. Herein, we demonstrate a magnetic bead-based, enzyme-linked immunosorbent assay (ELISA) using ~60 nL of human interleukin-6 (IL-6) sample. The wash buffer was introduced in the form of a wall-less virtual electrowetting channel by a syringe pump at the flow rate of 10 μL/min with ~100% bead retention rate. Critical parameters such as sample wash flow rate and bead retention rate were optimized for reliable assay results. A colorimetric readout was analyzed in the International Commission on Illumination (CIE) color space without the need for costly equipment. The concepts presented in this work are potentially applicable in rapid neonatal disease screening using a finger prick blood sample in a DMF platform. View Full-Text
Keywords: digital microfluidics; enzyme-linked immunosorbent assay (ELISA) digital microfluidics; enzyme-linked immunosorbent assay (ELISA)
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Liu, Y.; Papautsky, I. Heterogeneous Immunoassay Using Channels and Droplets in a Digital Microfluidic Platform. Micromachines 2019, 10, 107.

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