Analytical and Bioanalytical Chemistry

, Volume 399, Issue 1, pp 347–352 | Cite as

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

  • Dario Lombardi
  • Petra S. DittrichEmail author
Original Paper


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.


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



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.

Supplementary material

Movie S1

Droplet splitting at the T-junction, while magnetic beads are withdrawn to the side, where the magnet is placed.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

216_2010_4302_MOESM2_ESM.pdf (615 kb)
Supplementary Material (PDF 615 kb)


  1. 1.
    He XM, Carter DC (1992) Atomic structure and chemistry of human serum albumin. Nature 358:209–215CrossRefGoogle Scholar
  2. 2.
    Dumelin CE, Trussel S, Buller F, Trachsel E, Bootz F, Zhang Y, Mannocci L, Beck SC, Drumea-Mirancea M, Seeliger MW, Baltes C, Muggler T, Kranz F, Rudin M, Melkko S, Scheuermann J, Neri D (2008) A portable albumin binder from a DNA-encoded chemical library. Angew Chem Int Ed 47:3196–3201CrossRefGoogle Scholar
  3. 3.
    Lim YT, Lee KY, Lee K, Chung BH (2006) Immobilization of histidine-tagged proteins by magnetic nanoparticles encapsulated with nitrilotriacetic acid (NTA)-phospholipids micelle. Biochem Biophys Res Commun 344:926–930CrossRefGoogle Scholar
  4. 4.
    Shukoor MI, Natalio F, Tahir MN, Ksenofontov V (2007) H.A. Therese, P. Theato, H.C. Schroder, W.E. Muller, W. Tremel, Superparamagnetic gamma-Fe(2)O(3) nanoparticles with tailored functionality for protein separation. Chem Commun 44:4677–4679CrossRefGoogle Scholar
  5. 5.
    Marszall MP, Bucinski A (2010) A protein-coated magnetic beads as a tool for the rapid drug–protein binding study. J Pharm Biomed Anal 52:420–424CrossRefGoogle Scholar
  6. 6.
    Srinivasan B, Huang X (2008) Functionalization of magnetic nanoparticles with organic molecules: loading level determination and evaluation of linker length effect on immobilization. Chirality 20:265–277CrossRefGoogle Scholar
  7. 7.
    Yang C, Guan Y, Xing J, Jia G, Liu H (2006) Synthesis and protein immobilization of monodisperse magnetic spheres with multifunctional groups. React Funct Polym 66:263–273Google Scholar
  8. 8.
    Liu K, Xing J, Guan Y, Shan G, Liu H (2004) Synthesis of amino-silane modified superparamagnetic silica supports and their use for protein immobilization. Colloids Surf A 238:127–131CrossRefGoogle Scholar
  9. 9.
    Urban PL, Goodall DM, Bruce NC (2006) Enzymatic microreactors in chemical analysis and kinetic studies. Biotechnol Adv 24:42–57CrossRefGoogle Scholar
  10. 10.
    Valera FE, Quaranta M, Moran A, Blacker J, Armstrong A, Cabral JT, Blackmond DG (2010) The flow’s the thing… or is it? Assessing the merits of homogeneous reactions in flask and flow. Angew Chem Int Ed 49:2478–2485CrossRefGoogle Scholar
  11. 11.
    Dittrich PS, Manz A (2006) Lab-on-a-chip: microfluidics in drug discovery. Nat Rev Drug Discov 5:210–218CrossRefGoogle Scholar
  12. 12.
    Utada AS, Lorenceau E, Link DR, Kaplan PD, Stone HA, Weitz DA (2005) Monodisperse double emulsions generated from a microcapillary device. Science 308:537–541CrossRefGoogle Scholar
  13. 13.
    Urbanski JP, Thies W, Rhodes C, Amarasinghe S, Thorsen T (2006) Digital microfluidics using soft lithography. Lab Chip 6:96–104CrossRefGoogle Scholar
  14. 14.
    Thorsen T, Roberts RW, Arnold FH, Quake SR (2001) Dynamic pattern formation in a vesicle-generating microfluidic device. Phys Rev Lett 86:4163–4166CrossRefGoogle Scholar
  15. 15.
    Song H, Ismagilov RF (2003) Millisecond kinetics on a microfluidic chip using nanoliters of reagents. J Am Chem Soc 125:14613–14619CrossRefGoogle Scholar
  16. 16.
    Zheng B, Roach LS, Ismagilov RF (2003) Screening of protein crystallization conditions on a microfluidic chip using nanoliter-size droplets. J Am Chem Soc 125:11170–11171CrossRefGoogle Scholar
  17. 17.
    Chiu DT, Lorenz RM (2009) Chemistry and biology in femtoliter and picoliter volume droplets. Acc Chem Res 42:649–658CrossRefGoogle Scholar
  18. 18.
    Li L, Mustafi D, Fu Q, Tereshko V, Chen DL, Tice JD, Ismagilov RF (2006) Nanoliter microfluidic hybrid method for simultaneous screening and optimization validated with crystallization of membrane proteins. Proc Natl Acad Sci 103:19243–19248CrossRefGoogle Scholar
  19. 19.
    Song H, Tice JD, Ismagilov RF (2003) A microfluidic system for controlling reaction networks in time. Angew Chem Int Ed 42:768–772CrossRefGoogle Scholar
  20. 20.
    Dittrich PS, Jahnz M, Schwille P (2005) A new embedded process for compartmentalized cell-free protein expression and on-line detection in microfluidic devices. Chembiochem 6:811–814CrossRefGoogle Scholar
  21. 21.
    Song H, Chen DL, Ismagilov RF (2006) Reactions in droplets in microfluidic channels. Angew Chem Int Ed 45:7336–7356CrossRefGoogle Scholar
  22. 22.
    Brouzes E, Medkova M, Savenelli N, Marran D, Twardowski M, Hutchison JB, Rothberg JM, Link DR, Perrimon N, Samuels ML (2009) Droplet microfluidic technology for single-cell high-throughput screening. Proc Natl Acad Sci 106:14195–14200CrossRefGoogle Scholar
  23. 23.
    Gijs MA, Lacharme F, Lehmann U (2010) Microfluidic applications of magnetic particles for biological analysis and catalysis. Chem Rev 110:1518–1563CrossRefGoogle Scholar
  24. 24.
    Pamme N (2007) Continuous flow separations in microfluidic devices. Lab Chip 7:1644–1659CrossRefGoogle Scholar
  25. 25.
    Pamme N (2006) Magnetism and microfluidics. Lab Chip 6:24–38CrossRefGoogle Scholar
  26. 26.
    Shah GJ, Kim CJ (2009) Meniscus-assisted high-efficiency magnetic collection and separation for EWOD droplet microfluidics. J Microelectromech Syst 18:363–375CrossRefGoogle Scholar
  27. 27.
    Wang Y, Zhao Y, Cho SK (2007) Efficient in-droplet separation of magnetic particles for digital microfluidics. J Micromechanics Microengineering 17:2148–2156CrossRefGoogle Scholar
  28. 28.
    Qin D, Xia Y, Whitesides GM (1996) Rapid prototyping of complex structures with feature sizes larger than 20 μm. Adv Mater 8:3CrossRefGoogle Scholar
  29. 29.
    Clausell-Tormos J, Lieber D, Baret JC, El-Harrak A, Miller OJ, Frenz L, Blouwolff J, Humphry KJ, Koster S, Duan H, Holtze C, Weitz DA, Griffiths AD, Merten CA (2008) Droplet-based microfluidic platforms for the encapsulation and screening of Mammalian cells and multicellular organisms. Chem Biol 15:427–437CrossRefGoogle Scholar
  30. 30.
    Holtze C, Rowat AC, Agresti JJ, Hutchison JB, Angile FE, Schmitz CH, Koster S, Duan H, Humphry KJ, Scanga RA, Johnson JS, Pisignano D, Weitz DA (2008) Biocompatible surfactants for water-in-fluorocarbon emulsions. Lab Chip 8:1632–1639CrossRefGoogle Scholar
  31. 31.
    Moaddel R, Marszall MP, Bighi F, Yang Q, Duan X, Wainer IW (2007) Automated ligand fishing using human serum albumin-coated magnetic beads. Anal Chem 79:5414–5417CrossRefGoogle Scholar
  32. 32.
    Garstecki P, Fuerstman MJ, Stone HA, Whitesides GM (2006) Formation of droplets and bubbles in a microfluidic T-junction-scaling and mechanism of break-up. Lab Chip 6:437–446CrossRefGoogle Scholar
  33. 33.
    Boedicker JQ, Li L, Kline TR, Ismagilov RF (2008) Detecting bacteria and determining their susceptibility to antibiotics by stochastic confinement in nanoliter droplets using plug-based microfluidics. Lab Chip 8:1265–1272CrossRefGoogle Scholar
  34. 34.
    Lazar IM, Grym J, Foret F (2006) Microfabricated devices: a new sample introduction approach to mass spectrometry. Mass Spectrom Rev 25:573–594CrossRefGoogle Scholar
  35. 35.
    Fidalgo LM, Whyte G, Ruotolo BT, Benesch JL, Stengel F, Abell C, Robinson CV, Huck WT (2009) Coupling microdroplet microreactors with mass spectrometry: reading the contents of single droplets online. Angew Chem Int Ed Engl 48:3665–3668CrossRefGoogle Scholar
  36. 36.
    Siegel AC, Shevkoplyas SS, Weibel DB, Bruzewicz DA, Martinez AW, Whitesides GM (2006) Cofabrication of electromagnets and microfluidic systems in poly(dimethylsiloxane). Angew Chem Int Ed Engl 45:6877–6882CrossRefGoogle Scholar
  37. 37.
    Loun B, Hage DS (1994) Chiral separation mechanisms in protein-based HPLC columns. 1. Thermodynamic studies of (R)- and (S)-warfarin binding to immobilized human serum albumin. Anal Chem 66:3814–3822CrossRefGoogle Scholar

Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  1. 1.Department of Chemistry and Applied BiosciencesETH ZurichZurichSwitzerland

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