Ferromagnetic particles for an improved heterogeneous bioassay performance on a digital lab-on-a-chip

In this work, we report on a novel strategy to implement and to optimize heterogeneous bioassays on an electrowetting-on-dielectric (EWOD) digital lab-on-a-chip analysis platform, namely the use of ferromagnetic particles as functional carriers for biomolecules in combination with a highly efficient extraction protocol. This extraction protocol serves as an extension to the common operations of the ‘digital droplet toolkit’, consisting of droplet dispensing, movement, merging and splitting. This new droplet-based function allows the introduction of a very efficient washing step, extremely important in immunoassays. In addition, the magnetic particles enhance the mixing process inside the droplet when a rotating magnetic field is applied. The strength of both droplet manipulations with respect to heterogeneous assays is proven by the integration of two different bioassays (an IgG-immunoassay and an enzymatic assay for glucose) on the digital lab-on-a-chip platform.