Label-Free Quantification of Small-Molecule Binding to Membrane Proteins on Single Cells by Tracking Nanometer-Scale Cellular Membrane Deformation

ACS Nano. 2018 Feb 27;12(2):2056-2064. doi: 10.1021/acsnano.8b00235. Epub 2018 Feb 6.


Measuring molecular binding to membrane proteins is critical for understanding cellular functions, validating biomarkers, and screening drugs. Despite the importance, developing such a capability has been a difficult challenge, especially for small-molecule binding to membrane proteins in their native cellular environment. Here we show that the binding of both large and small molecules to membrane proteins can be quantified on single cells by trapping single cells with a microfluidic device and detecting binding-induced cellular membrane deformation on the nanometer scale with label-free optical imaging. We develop a thermodynamic model to describe the binding-induced membrane deformation, validate the model by examining the dependence of membrane deformation on cell stiffness, membrane protein expression level, and binding affinity, and study four major types of membrane proteins, including glycoproteins, ion channels, G-protein coupled receptors, and tyrosine kinase receptors. The single-cell detection capability reveals the importance of local membrane environment on molecular binding and variability in the binding kinetics of different cell lines and heterogeneity of different cells within the same cell line.

Keywords: binding kinetics; label-free detection; membrane proteins; microfluidics; single-cell analysis.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Biomechanical Phenomena / drug effects
  • Cell Line
  • Cell Membrane / drug effects
  • Cell Membrane / metabolism
  • Drug Evaluation, Preclinical / instrumentation
  • Equipment Design
  • Humans
  • Kinetics
  • Lab-On-A-Chip Devices*
  • Membrane Proteins / metabolism*
  • Protein Binding
  • Single-Cell Analysis / instrumentation*
  • Small Molecule Libraries / metabolism*
  • Small Molecule Libraries / pharmacology


  • Membrane Proteins
  • Small Molecule Libraries