Electrochemiluminescence at Functionalized Trapped Microbeads in Microfluidic Channels

Electrochemiluminescence (ECL) is successfully combined with microbead-based immunoassays for quantification of a wide range of biomarkers. Herein, a microfluidic platform was developed to study the electrochemiluminescence (ECL) emission of a model microbead-based system under controlled flow conditions. The microbeads, functionalized with tris(2,2'-bipyridine)ruthenium(II) as luminophore, were entrapped by micropillars in a microfluidic channel and exposed to a circulating solution of tri<i>-n</i>-propylamine coreactant. The confined space of the microchannel combined with convective mass transport allowed the enhancement of the ECL signal emitted by the entrapped beads. Analysis of the light profiles from isolated beads showed that the performance of the heterogeneous ECL pathway was greatly influenced by the flow rate. Therefore, mass transport was found to be essential for tuning the ECL intensity of these systems, as it leads to a 4-fold increase in ECL intensity from diffusive to convective regimes. These results already highlight real opportunities for improving ECL immunoassays through novel flow-based strategies.