A study of the incubation of microbead agglutination assays in a microfluidic system

This work reports on a quantitative study of the incubation of a microbead-based agglutination assay inside a microfluidic system. In this system, a droplet (1.25μL) consisting of a mixture of functionalized microbeads and analyte is flowed through a 0.51mm internal diameter silicone tube. Hydrodynamic forces alone produce a very efficient mixing of the beads within the droplet. We tested the agglutination at different speeds and show a robust response at the higher range of speeds (150 - 200μL/min), while also reaching a completion in the agglutination process. At these velocities, a length of 180cm is shown to be sufficient to confidently measure the agglutination assay, which takes between 2.5 - 3 minutes. This high throughput quantification method has the potential of accelerating the measurements of various types of biomarkers, which can greatly benefit the fields of biology and medicine.

I. Introduction

In the past years, there has been an increase in the use of microbead-based immunoagglutination assays for the detection of diverse chemicals and biomarkers [1]–[3]. A large array of tests and assays are commercially available, capable of probing infectious diseases, viral and bacterial loads, as well as proteins and biomarkers [4]. Immunoagglutination assays typically consist of beads, in the scale of a few microns, that have been functionalized with with an antibody. These beads, in the presence of a matching antigen, will bind to each other and aggregate, resulting in clumps that are visible to the naked eye. Their simplicity result in robust protocols, and are a good alternative to enzime-linked immunoabsorbent assays (ELISA) [5], which typically require several washing steps and more time-consuming protocols.