Enhanced blood-brain barrier opening induced by focused ultrasound combined with microbubble clusters trapped by an acoustic vortex tweezer

Focused ultrasound (FUS) combined with microbubbles (MBs) represents a noninvasive, targeted approach for transiently opening the blood-brain barrier (BBB). While higher MB concentrations can enhance BBB permeability, they also raise the risk of adverse effects such as erythrocyte extravasation. In this study, acoustic vortex (AV) manipulation of MBs was integrated with FUS-mediated BBB opening. The results demonstrated that dispersed MBs could be effectively clustered by an AV tweezer in multi-well plates. Compared with FUS applied to dispersed MBs, the combination of AV, FUS, and MBs required lower acoustic pressure, achieved higher BBB opening efficiency, and elicited significantly stronger stable cavitation. In addition, both pore density and size on cell membranes were greater in the AV + FUS + MB group relative to the FUS + MB group. Importantly, temperature elevation was minimal and cell viability was preserved. These findings suggest that combining FUS with MB clusters trapped by an AV tweezer offers a promising and efficient strategy for BBB opening.