Mapping microbubble viscosity using fluorescence lifetime imaging of molecular rotors

Area of Science:

• Biomedical Engineering
• Materials Science
• Optical Imaging

Background:

• Microbubbles are crucial ultrasound contrast agents.
• Advanced applications require precise characterization of microbubble viscoelastic properties.
• Current methods for quantifying these properties are limited.

Purpose of the Study:

• To present a novel, non-destructive method for quantifying microbubble shell viscoelasticity.
• To investigate the influence of shell composition and manufacturing on viscosity.
• To map viscosity variations within individual microbubble shells.

Main Methods:

• Incorporation of a "molecular rotor" fluorophore into the microbubble shell.
• Utilizing fluorescence lifetime imaging to measure local viscosity.
• Analyzing viscosity distributions across microbubble populations and individual shells.

Main Results:

• Demonstrated that microbubble shell viscosities vary significantly among different microbubbles.
• Showed that shell composition and manufacturing processes impact viscosity.
• Revealed heterogeneous viscosity distributions within individual microbubble shells, even with uniform surfactant composition.

Conclusions:

• The molecular rotor fluorescence lifetime imaging technique provides accurate, non-destructive quantification of microbubble shell viscosity.
• Understanding and controlling microbubble shell viscosity is critical for optimizing their performance in advanced ultrasound imaging and therapeutic applications.
• This method enables detailed characterization essential for developing next-generation microbubble-based technologies.