Combining drug-loaded nanobubbles and Extracorporeal Shock Waves for difficult-to-treat cancers

Despite the general great improvement in cancer therapy, to date, some aggressive tumors are still without an efficient therapy. Therefore, accurate delivery of anti-cancer drugs is a very important goal in order to obtain a successful therapy and reduce systemic side effects. Nanobubbles (NBs) are spherical core/shell vesicles filled by a gas with sizes in the nanometer order of magnitude. They have gained an increasing attention for drug delivery, because they can be versatile multifunctional carriers for the targeted release of gases, drugs and genes. Particularly, NBs can carry loaded drugs to the tumor site through the blood stream, taking advantage of the enhanced permeability and retention effect, due to the defective vascular architecture of the tumor (Fang et al. 2011). Unfortunately, vessel leakage, the absence of a functional lymphatic system and an increased extracellular matrix frictional resistance may limit drug delivery (Azzi et al. 2013, Carmeliet and Jain 2011). To overcome this problem, a better drug release to cancer tissues can be obtained by combining physical triggers (e.g. ultrasounds, US) with NBs (Gao et al. 2008, Collis et al. 2010, Cavalli et al. 2012, Cavalli et al. 2016, Argenziano et al. 2017). Indeed, US causes bubble cavitation resulting in cell sonoporation and allowing the extravasation of molecules (Collis et al. 2010).