What is Microfluidic Diffusional Sizing (MDS)?

Quantify and characterize any protein interaction in complex backgrounds, close to in vivo conditions

What is Microfluidic Diffusional Sizing (MDS) Technology?

Microfluidic diffusion technology (MDS) brings a new tool to the analytical characterization toolbox: a different approach that enables the analysis of protein interactions close to in vivo conditions.

Scientists can now determine affinity of interaction (KD), concentration of bound protein, and stoichiometric information, in solution, and all in a single experiment, whether using simple biological buffer systems or complex backgrounds such as serum, plasma and cell lysates.


What is Microfluidic Diffusional Sizing (MDS) Technology?

Watch the video below to understand how Microfluidic Diffusional Sizing works:


MDS enables the quantification of protein interactions in complex backgrounds, providing independent information on affinity, concentration, on-target / off-target binding, and stoichiometry. This information complements data obtained from other characterization techniques, ensuring a better understanding of a protein interaction and its influencing factors. By enabling scientists to go beyond simple studies of KD and concentration, MDS facilitates more informed decisions, from basic research through to therapeutic development.

Microfluidic diffusional sizing (MDS) exploits the unique properties of “flow” in microfluidic channels — specifically laminar flow, where streams can flow alongside one another with no convective mixing. MDS measures molecular size (hydrodynamic radius), and changes in size indicate binding events.

A more detailed description of how MDS works can be found here.

MDS measurements are captured using the Fluidity One Platform.


What are users saying about MDS?

See what you can discover

Quantify and characterize any protein interaction – even in complex backgrounds, even with challenging targets

Measure protein interactions directly in complex sample backgrounds

Antibody-affinity profiling in serum – SARS-COV-2 anti-spike S1 antibody against SARS-CoV-2 RBD (receptor binding domain)

  • Measure close to physiologically-relevant conditions
  • Reduce or eliminate time-consuming purification steps
  • Minimize risk of dilution effects
  • Minimize sample consumption – 60-100 μL* sample per KD


Achieve consistent results across sample types, whether working with buffers or complex background

Antibody-affinity profiling – SARS-COV-2 anti-spike S1 antibody against SARS-CoV-2 RBD

  • Measurements in buffer or complex backgrounds, provide corresponding results
  • Quantitative analysis of protein–protein interactions (KD and binding-site concentrations)
  • Determine affinity, KD, and absolute concentration of antibody binding sites


Determine affinity and concentration with one technique

Immunoprofiling in serum during infection – Characterizing the immune response to viral infections

A collaboration with Prof. Adriano Aguzzi and Prof. Tuomas Knowles.

  • No correlation between affinity or concentration and disease severity – Hospitalized and non-hospitalized COVID-19 patients in same cluster
  • Affinity KD spans significantly wider range than concentration



Obtain comparable results to other characterization techniques

PD-1/PD-L1 interaction – critical in control of autoimmune response

KD (µM)TechniqueReference
2.2ITCCheng et al., JBC (2013)
3.9SPR equilibriumZhang et al., Immunity (2004)
0.7SPR equilibriumLatchman et al., Nat. Imm. (2001)
7.2MSTMagnez et al., Sci. Rep. (2017)

A comparison of binding affinity values for PD-1/PD-L1 from a range of biophysical techniques


Protein-DNA interactions

KD of aptamer-protein interactions

  • No calibration or specialist preparation required
  • KD successfully calculated for each aptamer binding
  • KD values in agreement with reported literature values


Reveal changes in molecular conformation

Follow changes in hydrodynamic radius in solution: Protein A:IgG interaction

  • Determine size of SpA:IgG complex in solution
  • Microfluidic diffusion sizing confirmed SpA:IgG 1:3
  • Experimental data in agreement with hypothetical Rh values from molecular modelling (PyMOL*)

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The Fluidity One platform enables quantification and characterization of any protein interaction –

even in complex backgrounds or with challenging targets

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