UC Irvine

Here we present a fully integrated centrifugal microfluidic device that allows for automation of an enzyme-linked immunosorbent assay (ELISA), a common analytical biochemistry assay that would normally be performed either through labor-intensive and time-consuming protocols or by large and expensive analyzers. The system features a novel wireless readout approach that enables continuous, real-time electrochemical measurements with low levels of noise and high stability, even when the microfluidic disc is spinning at high velocities. Furthermore, redox cycling-amplified electrochemical detection is achieved by using interdigitated electrode arrays (IDEAs) as the sensing electrodes. We report that imposing flow over the electrodes by spinning the disc leads to improved sensor performance: a sensitivity of 6.99μA/mM and a limit of detection of 9.23nM are achieved at a slow flow rate of 203.4μL/min, which was demonstrated using the ferri-ferrocyanide redox-couple as the analyte solution. Prior to electrochemical detection, automated sample and reagent handling are achieved by designing a microfluidic system to release liquids sequentially, utilizing single-shot optofluidic valves that are actuated by a low power laser. High success rate of valve opening and fine tuning of spin speed enabled completion of the required assay steps on the disc. As a model system, antibody against Plasmodium, a marker of malaria, was used as the target biomolecule for detection. Aside from automating the assay, the platform allowed for a 1.5-fold increase in sensitivity in comparison to the off-disc protocol, which is attributed to the enhanced mixing conditions and flow-enhanced mass transport that happen on the disc.