WHEN ULTRASOUND MEETS MICROBUBBLES: ENHANCEMENT OF BLOOD-BRAIN BARRIER PERMEABILITY IN AN <EM>IN-VITRO</EM> MODEL AND IN MICE

The blood–brain barrier (BBB) is a highly selective interface that protects the brain from circulating pathogens and toxins, but also severely limits the delivery of therapeutic agents to the central nervous system. Microbubble-assisted ultrasound (MB-assisted US) represent a promising non-invasive strategy to transiently open the BBB and enhance drug delivery. This study investigated the ability of MB-assisted US to permeabilize an in-vitro endothelial barrier model and to induce BBB opening in mice. In-vitro, MB are added to Transwell^® inserts, containing endothelial cells, and an US sequence (1 MHz, 1 ms PRP, 5% DC, 0.4 MPa PNP, 2 min) was applied. Endothelial barrier integrity was assessed by transendothelial electrical resistance (TEER) measurements and lucifer yellow (LY) permeability immediately, 24 h and 48 h after treatment. MB-assisted US induced a significant decrease in TEER accompanied by increased LY transport, both of which returned to baseline values within 48 h, indicating a reversible permeabilization. In-vivo, mice received an intravenous injection of MB followed US sequence (1.1 MHz, 1 s PRP, 1% DC, 0.3 MPa PNP, 30 s), and Evans blue was subsequently administered. Dye extravasation was observed in the brains of treated mice but not in controls, demonstrating localized BBB opening. Overall, these results demonstrate that MB-assisted US enables transient and reversible enhancement of endothelial permeability in-vitro and effective BBB opening in-vivo, highlighting its potential for controlled drug delivery strategies in the context of neurodegenerative diseases.