Bilayer aggregate microstructure determines viscoelasticity of lung surfactant suspensions

Clara O Ciutara, Joseph A. Zasadzinski

Research output: Contribution to journalArticlepeer-review

4 Scopus citations


Neonatal respiratory distress syndrome (NRDS) is treated by intratracheal delivery of suspensions of animal-derived lung surfactant in saline. Lung surfactants are extracted via organic solvents from animal lung lavage, followed by solvent removal and surfactant re-hydration to form multi-bilayer particles suspended in saline. Following intra-tracheal administration, the surfactant suspension spreads throughout the lungs by surface tension gradient induced flow; the spreading rate is limited by suspension viscoelasticity. Here we examine the rheology of three clinical lung surfactant suspensions: Survanta (bovine lung), Curosurf (porcine lung), and Infasurf (calf lung). These surfactants have widely different rheological properties that depend on the lipid composition and bilayer organization. The steady shear viscosity is related to the bilayer particle volume fraction as for a suspension of hard spheres, but the lipid volume fraction is not simply related to the mass loading. Optical and electron microscopy and small angle X-ray scattering show that the viscosity variation is due to the temperature and composition dependent bilayer aggregate shapes and internal particle organization. Survanta forms crystalline bilayers at 37 °C, resulting in high aspect ratio asymmetric particles. Infasurf forms aggregates of unilamellar vesicles containing water pockets, while Curosurf forms onion-like multi-layered liposomes. While the mass loading of the three clinical surfactants is different, the different bilayer organization causes the particle volume fractions to be similar. Adding polyethylene glycol dehydrates and partially flocculates the bilayer aggregates in all suspensions, leading to smaller particle volume fractions and a reduced suspension viscosity even though the solvent viscosity increases almost six-fold.

Original languageEnglish (US)
Pages (from-to)5170-5182
Number of pages13
JournalSoft Matter
Issue number20
StatePublished - May 28 2021

Bibliographical note

Funding Information:
This project was supported by National Institutes of Health Grants HL 51177, HL 135065 and NSF Grant CBET 170378. The authors thank H. Warriner for the SAXS measurements, G. Braun for the freeze-fracture imaging and M. Calabrese and C. Macosko for help in interpreting the rheology data.

Publisher Copyright:
© The Royal Society of Chemistry.


  • Animals
  • Cattle
  • Lung
  • Pulmonary Surfactants
  • Surface-Active Agents
  • Suspensions
  • Swine
  • Viscosity

PubMed: MeSH publication types

  • Journal Article


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