A new 3D in-vitro vascular model for studying ultrasound-microbubble-mediated endothelial permeabilization

Abstract

Cancer therapy efficacy is often limited by the blood vessel endothelium, which hinders drug delivery. Ultrasound (US) and microbubbles (MBs) can enhance drug delivery by increasing endothelial permeability through MB cavitation, but the underlying mechanisms are not yet fully elucidated. While 2D in vitro vascular models have been used to study the relation between US-parameters, cavitation regimes, and impaired endothelial barrier function, they fail to replicate 3D in vivo conditions. Existing 3D models better reflect physiological cellular behavior but are often not US-compatible, making them unsuitable for studying USMB-therapy. In this study, we developed and validated a new, US-compatible 3D vascular model for the perfused culture of a microvessel suitable for barrier function assessment, as well as an experimental setup for sonicating the model with variable US parameters and monitoring of USMB-therapy by detecting cavitation signals. The 3D design allowed for microvessel development but its ability to support development until confluency and vessel maintenance could not be validated. The experimental set-up enabled correlating USMB parameters with cavitation regimes; stable cavitation started at US-pressures between 0.2-0.3 MPa, and increased significantly with pressure until 0.5 MPa. Inertial cavitation was minimally present between 0.2-0.4 MPa, and started to increase significantly above 0.4 MPa. The transmitting US-transducer used did not permit assessment of USMB-mediated compromised barrier integrity. In conclusion, the established platform allows for microvessel development but requires protocol improvements to support development until confluency. Furthermore, the platform allows for measuring and correlating US-parameters with cavitation regimes, but requires a focused US-transducer to also correlate changes in endothelial barrier integrity. Once the improvements are implemented, the established platform can be used for large scale studying of USMB-mechanisms, aiding its clinical translation and thereby improving drug delivery in patients.