Droplet microfluidics with magnetic beads: a new tool to investigate drug–protein interactions


In this study, we give the proof of concept for a method to determine binding constants of compounds in solution. By implementing a technique based on magnetic beads with a microfluidic device for segmented flow generation, we demonstrate, for individual droplets, fast, robust and complete separation of the magnetic beads. The beads are used as a carrier for one binding partner and hence, any bound molecule is separated likewise, while the segmentation into small microdroplets ensures fast mixing, and opens future prospects for droplet-wise analysis of drug candidate libraries. We employ the method for characterization of drug–protein binding, here warfarin to human serum albumin. The approach lays the basis for a microfluidic droplet-based screening device aimed at investigating the interactions of drugs with specific targets including enzymes and cells. Furthermore, the continuous method could be employed for various applications, such as binding assays, kinetic studies, and single cell analysis, in which rapid removal of a reactive component is required.

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The authors acknowledge Stefanie Krämer for providing the radio-labeled 14C-warfarin and making the scintillation counter available to us. The project was financially supported by the European Research Council under the 7th Framework Program (ERC Starting Grant, project no. 203428, nμLIPIDS). We thank Benjamin Cvetkovic and Daniel Schaffhauser for the preparation of the master form and Phillip Kuhn and Simon Küster for the proofreading of the manuscript.

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Correspondence to Petra S. Dittrich.

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Droplet splitting at the T-junction, while magnetic beads are withdrawn to the side, where the magnet is placed. (AVI 1051 kb)

Movie S1

Droplet splitting at the T-junction, while magnetic beads are withdrawn to the side, where the magnet is placed. (AVI 1051 kb)

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Lombardi, D., Dittrich, P.S. Droplet microfluidics with magnetic beads: a new tool to investigate drug–protein interactions. Anal Bioanal Chem 399, 347–352 (2011).

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  • Microfluidics
  • Digital microfluidics
  • Droplet splitting
  • Magnetic beads
  • Serum albumin
  • Warfarin
  • Equilibrium constants
  • Drug–protein interactions