Can sonication enhance release from liquid-core capsules with a hydrogel membrane?

Area of Science:

• Materials Science
• Biomaterials Engineering
• Acoustics

Background:

• Hydrogel capsules offer potential for controlled release applications.
• Understanding the impact of external stimuli like sonication is crucial for their application.
• Fabrication of millimetric capsules with hyperelastic alginate membranes presents unique challenges.

Purpose of the Study:

• To investigate the effects of sonication on the mechanical and release properties of novel hydrogel capsules.
• To determine the threshold for sonication-induced capsule rupture.
• To elucidate the mechanism behind sonication-enhanced mass release.

Main Methods:

• Development of a new fabrication process for millimetric alginate-membrane capsules with viscous liquid cores.
• Mechanical testing of capsules subjected to varying sonication intensities and durations.
• Quantification of mass release (blue dextran) from sonicated capsules.
• Analysis of membrane porosity and recovery post-sonication.

Main Results:

• Sonication at high intensities or long durations induces membrane fatigue, leading to capsule rupture.
• Below the rupture threshold, sonication does not cause lasting changes in capsule mechanical properties.
• Mass release is proportional to sonication duration and pressure wave amplitude, attributed to acoustic streaming.
• Temporary increases in membrane porosity are observed, which reverse after sonication cessation.

Conclusions:

• Hydrogel capsule integrity and mechanical properties are maintained below a critical sonication threshold.
• Sonication can enhance mass release from hydrogel capsules via acoustic streaming, with temporary porosity changes.
• The alginate membrane demonstrates resilience, recovering its properties after ultrasonic stimulation, suggesting potential for controlled release applications.