Microbubble Generation in Phase-Shift Nanoemulsions used as Anticancer Drug Carriers

Area of Science:

• Materials Science
• Colloid and Surface Chemistry
• Biophysics

Background:

• Perfluoropentane nanoemulsions are utilized in various biomedical applications, including as ultrasound contrast agents.
• Controlling droplet-to-bubble transitions is essential for optimizing the performance and safety of these nanoemulsions.
• Understanding the physical factors and mechanisms governing these transitions is critical for further development.

Purpose of the Study:

• To investigate the physical factors inducing droplet-to-bubble transitions in block copolymer-stabilized perfluoropentane nanoemulsions.
• To elucidate the mechanisms responsible for bubble generation, growth, and irreversibility.
• To evaluate the influence of matrix properties (liquid vs. gel) and pre-existing bubbles on the transition process.

Main Methods:

• Evaluation of heat, ultrasound irradiation, and fine-gauge needle injections as transition triggers.
• Analysis of bubble generation and growth mechanisms, including liquid-to-gas transition, coalescence, and Oswald ripening.
• Investigation of ultrasound-induced transitions in liquid versus gel matrices and the effect of pre-existing bubbles.

Main Results:

• Ultrasound irradiation was identified as the most efficient trigger for droplet-to-bubble transition.
• Bubble coalescence and Oswald ripening were identified as key mechanisms leading to irreversible transitions.
• Ultrasound-induced transitions were inhibited in gel matrices but catalyzed by large pre-existing bubbles at specific frequencies.

Conclusions:

• Ultrasound is a potent tool for inducing droplet-to-bubble transitions in perfluoropentane nanoemulsions.
• The transition process is complex, involving multiple mechanisms that contribute to its irreversibility.
• The findings have significant implications for the design and application of nanoemulsion-based therapies, particularly those utilizing ultrasound.