Nonuniform Crowding Enhances Transport

Matthew Collins, Farzad Mohajerani, Subhadip Ghosh, Rajarshi Guha, Tae Hee Lee, Peter J. Butler, Ayusman Sen, Darrell Velegol

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


The cellular cytoplasm is crowded with macromolecules and other species that occupy up to 40% of the available volume. Previous studies have reported that for high crowder molecule concentrations, colloidal tracer particles have a dampened diffusion due to the higher solution viscosity. However, these studies employed uniform distributions of crowder molecules. We report a scenario, previously unexplored experimentally, of increased tracer transport driven by a nonuniform concentration of crowder macromolecules. In gradients of a polymeric crowder, tracer particles undergo transport several times higher than that of their bulk diffusion rate. The direction of the transport is toward regions of lower crowder concentration. Mechanistically, hard-sphere interactions and the resulting volume exclusion between the tracer and crowder increase the effective diffusion by inducing a convective motion of tracers, which we explain through modeling. Strikingly, soft deformable particles show even greater enhancement in transport in crowder gradients compared to similarly sized hard particles. Overall, this demonstration of enhanced transport in nonuniform distributions of crowders is anticipated to clarify aspects of multicomponent intracellular transport.

Original languageEnglish (US)
Pages (from-to)8946-8956
Number of pages11
JournalACS nano
Issue number8
StatePublished - Aug 27 2019

All Science Journal Classification (ASJC) codes

  • General Materials Science
  • General Engineering
  • General Physics and Astronomy


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