Stability of Monodisperse Phospholipid-Coated Microbubbles Formed by Flow-Focusing at High Production Rates

Tim Segers*, Leonie De Rond, Nico De Jong, Mark Borden, Michel Versluis

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

40 Citations (Scopus)

Abstract

Monodisperse microbubble ultrasound contrast agents may dramatically increase the sensitivity and efficiency in ultrasound imaging and therapy. They can be produced directly in a microfluidic flow-focusing device, but questions remain as to the interfacial chemistry, such as the formation and development of the phospholipid monolayer coating over time. Here, we demonstrate the synthesis of monodisperse bubbles with radii of 2-10 μm at production rates ranging from 104 to 106 bubbles/s. All bubbles were found to dissolve to a stable final radius 2.55 times smaller than their initial radius, independent of the nozzle size and shear rate, indicating that the monolayer self-assembles prior to leaving the nozzle. The corresponding decrease in surface area by a factor 6.6 reveals that lipid molecules are adsorbed to the gas-liquid interface in the disordered expanded state, and they become mechanically compressed by Laplace pressure-driven bubble dissolution to a more ordered condensed state with near zero surface tension. Acoustic characterization of the stabilized microbubbles revealed that their shell stiffness gradually increased from 0.8 to 2.5 N/m with increasing number of insonations through the selective loss of the more soluble lipopolymer molecules. This work therefore demonstrates high-throughput production of clinically relevant monodisperse contrast microbubbles with excellent control over phospholipid monolayer elasticity and microbubble resonance.

Original languageEnglish
Pages (from-to)3937-3944
JournalLangmuir: the ACS journal of surfaces and colloids
Volume32
Issue number16
DOIs
Publication statusPublished - 2016
Externally publishedYes

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