A plug-based microfluidic approach was used to perform
multiple agglutination assays in parallel without crosscontamination and using only microliter volumes of blood.
To perform agglutination assays on-chip, a microfluidic
device was designed to combine aqueous streams of
antibody, buffer, and red blood cells (RBCs) to form
droplets 30-40 nL in volume surrounded by a fluorinated
carrier fluid. Using this approach, proof-of-concept ABO
and D (Rh) blood typing and group A subtyping were
successfully performed by screening against multiple
antigens without cross-contamination. On-chip subtyping
distinguished common A1 and A2
RBCs by using a lectinbased dilution assay. This flexible platform was extended
to differentiate rare, weakly agglutinating RBCs of A
subtypes by analyzing agglutination avidity as a function
of shear rate. Quantitative analysis of changes in contrast
within plugs revealed subtleties in agglutination kinetics
and enabled characterization of agglutination of rare blood
subtypes. Finally, this platform was used to detect bacteria, demonstrating the potential usefulness of this assay
in detecting sepsis and the potential for applications in
agglutination-based viral detection. The speed, control,
and minimal sample consumption provided by this technology present an advance for point of care applications,
blood typing of newborns, and general blood assays in
small model organisms
