Meijlink, B. | Search bioRxiv

bioRxiv2024

Ultrasound-activated microbubbles mediate F-actin disruptions and endothelial gap formation during sonoporation

Locally opening up the endothelial barrier in a safe and controlled way is beneficial for drug delivery into the extravascular tissue. Although ultrasound-induced microbubble oscillations can affect endothelial barrier integrity, the mechanism remains unknown. Here we uncover a new role for F-actin in microbubble-mediated endothelial gap formation. Unique simultaneous high-resolution confocal microscopy and ultra-high-speed camera imaging (10 million frames per second) reveal that oscillating microbubbles (radius 1.3-3.8 {micro}m) induce sonoporation in all cells in which F-actin remodeling occurred. F-actin disruption only mainly resulted in tunnel formation (75%) and F-actin stress fiber severing and recoil mainly resulted in cell-cell contact opening within 15 s upon treatment (54%) and tunnel formation (15%). Stress fiber severing occurred when fibers were within reach of the microbubbles maximum radius during oscillation, requiring normal forces of [≥]230 nN. Together, these findings reveal a novel mechanism of microbubble-mediated drug delivery, which associates with the underlying cytoskeletal organization.

bioengineering↗

bioRxiv2024

Characterizing microbubble-mediated permeabilization in a vessel-on-a-chip model

Drug transport from blood to extravascular tissue can locally be achieved by increasing the vascular permeability through ultrasound-activated microbubbles. However, the mechanism remains unknown, including whether short and long cycles of ultrasound induce the same onset rate, spatial distribution, and amount of vascular permeability increase. Accurate models are necessary for insights into the mechanism so a microvessel-on-a-chip is developed with a membrane-free extravascular space. Using these microvessels-on-a-chip, we show distinct differences between 2 MHz ultrasound treatments with 10 or 1000 cycles. The onset rate is slower for 10 than 1000 cycles, while both cycle lengths increase the permeability in spot-wise patterns without affecting cell viability. Significantly less vascular permeability increase and sonoporation are induced for 10 versus 1000 cycles at 750 kPa (i.e., highest studied peak negative acoustic pressure (PNP)). The PNP threshold for vascular permeability increases is 750 versus 550 kPa for 10 versus 1000 cycles, while this is 750 versus 220 kPa for sonoporation. Vascular permeability increases do not correlate with v{beta}3-targeted microbubble behavior, while sonoporation correlates with v{beta}3-targeted microbubble clustering. In conclusion, the further mechanistic unraveling of vascular permeability increase by ultrasound-activated microbubbles in a developed microvessel-on-a-chip model aids safe and efficient development of microbubble-mediated drug transport.

bioengineering↗