Ultrasound cavitation of microbubbles for an in vitro study of drug delivery

In traditional drug delivery system, the uptake of molecules suffers ofpoor efficiency due to the low permeability of the endothelial barrier. Methods combining focused ultrasound and micro bubbles (MBs) offer the unique... [ view full abstract ]

In traditional drug delivery system, the uptake of molecules suffers ofpoor efficiency due to the low permeability of the endothelial barrier. Methods combining focused ultrasound and micro bubbles (MBs) offer the unique capability of non-invasively, locally and transiently open the endothelial barrier (Hernot S. and Klibanov A.L. 2008). MBs injected into the bloodstream undergo volume oscillations under ultrasound irradiation and possibly collapse. The resulting mechanical action induces a transient increase of barrier permeability due to the increase of inter-cellular spaces facilitating drug extravasation into the site of interest. The goal of this project is to induce cavitation of MBs (SonoVue®) in a microfluidic device (Fig.1) specially designed (DeosarkarP.S. et All. 2015) to investigate the effects of MBs behaviour on the endothelial barrier. The device is previously cultured with HUVECs cells with a reliable and reproducible protocol (Fig.2). Quantification of membrane permeability is evaluated through measurements of fluorescent dye diffusion towards a pores membrane with a confocal microscope operated in epi-fluorescence mode (Fig.3). The diffusion of the dye for a free-cell device was first evaluated to optimize the method. Afterwards, the permeability of cell-free device was compared to the permeability of the HUVECs cultured device. As expected, a decrease of the permeability value in presence of the biological barrier was observed (Fig.4).

The in vitro acoustic setup consists of an ultrasound transducer driven by a function generator through a power amplifier. It is designed and adapted to host the bio-chip, the piezoelectric transducers within a water-filled, temperature-controlled chamber located on the microscope stage. In order to investigate the effects of ultrasound MBs cavitation on the barrier permeability, the same experimental methodology will be adopted in the HUVECs cultured device with MBs with diameter range of 2-10 μm injected in the vascular channel and irradiated with ultrasounds.

The combination of the proposed high fidelity biomimetic device with the possibility to control the response of MBs to ultrasound has the great potential to allow the study of cavitation-enhanced permeability of the endothelium improving the efficiency in targeted drug delivery and giving a tool suitable for clinical trial of new medicines.