Cross-scale mechanistic insights into ultrasound pulse-length dependent BBB opening.

Area of Science:

• Biomedical Engineering
• Neuroscience
• Pharmacology

Background:

• Ultrasound-mediated blood-brain barrier (BBB) opening is a promising technique for targeted brain drug delivery.
• The precise mechanisms governing ultrasound-induced BBB modulation remain incompletely understood.

Purpose of the Study:

• To elucidate the real-time, cross-scale mechanisms of ultrasound pulse effects on microbubble dynamics, endothelial bioeffects, and BBB opening.
• To differentiate the outcomes of long versus short ultrasound pulses on BBB permeability and recovery.

Main Methods:

• High-speed imaging to observe microbubble dynamics and cavitation.
• In vivo two-photon microscopy in mouse models to assess dextran extravasation and endothelial cell integrity.
• Correlation of biophysical parameters with observed biological effects.

Main Results:

• Long ultrasound pulses induced heterogeneous microbubble coalescence, stable cavitation with cyclic jetting, leading to localized endothelial detachment and irreversible sonoporation.
• Short ultrasound pulses resulted in uniform bubble dynamics, reversible sonoporation, calcium signaling, uniform drug delivery, and rapid BBB recovery.
• First visualization of endothelial cell loss in vivo.

Conclusions:

• Ultrasound pulse characteristics critically dictate microbubble behavior and subsequent BBB opening outcomes.
• Short pulses offer a more controlled and reversible method for BBB opening, enhancing drug delivery efficiency and safety.
• These findings provide crucial insights for optimizing ultrasound-based BBB opening technologies.