Study of nanocrystals activated by acoustic stimuli for anticancer therapy

Cancer is the second worldwide cause of death after cardiovascular diseases. The treatments offered by conventional medicine, do not appear to be entirely effective for the eradication of the cancer and they can cause significant side effects. After the advent of nanotechnologies, their use in the medical field has highlighted the potential of nanomedicine, the application of nanomaterials for health and medicine. More specifically, smart nanoparticles have been increasingly studied thanks to their multifunctional properties that can provide rapid diagnosis, effective therapies and even their combination, labelled as theranostics. This is the context in which this Master Thesis is inserted. Among the available nanomaterials, zinc oxide nanoparticles (ZnO NPs) are widely used in biomedical applications thanks to their chemical and physical features, like semiconducting, piezoelectric and antibacterial properties. Moreover, ZnO, in its micrometric size, has been Generally Recognized As Safe (GRAS) by the Food and Drug Administration (FDA). Thanks to their deep penetration potential into tissues, Ultrasounds (US) are widely used in medicine and clinical practice and are now emerging as useful technology for activating certain nanomaterials for therapy against specific diseases, such as cancer. Sonodynamic Therapy (SDT) represents a novel approach that offers the potential for selectively eliminating solid tumors in a non-invasive manner. This therapy involves the administration of a sonosensitiser agent and the subsequent exposition to US waves, in order to enhance cavitation and induce greater Reactive Oxygen Species (ROS) generation, intensifying the oxidative stress in the target areas. To improve new and targeted cancer therapies, it is crucial to exploit the combination of NPs and US and in particular the main topic of this Master Thesis is to understand the mechanisms by which ZnO nanocrystals (NCs) generate ROS in synergy with ultrasound waves. More precisely, the present Thesis considers a biocompatible nanosized construct, composed by zinc oxide nanocrystals doped with iron atoms, and then further functionalized with capping agents, chemical functional units, sonochemosensitizers, and finally lipid bilayers, to provide colloidal stability, biocompatibility to cells and improved ROS production. The primarily aim of this master's thesis is to characterize the synergy between the different formulations of ZnO-based NPs and ultrasound, describing and measuring the effects of the produced inertial cavitation and thus of free radicals. Furthermore, the possible dissolution of the nanoparticles in biologically-relevant media has been evaluated and their cytotoxic effects coupled with ultrasounds irradiation have been tested in vitro on osteosarcoma 2D and 3D cell models. In conclusion, a wider understanding about the the synergistic effects between the different ZnO NPs nano-constructs and ultrasound waves has been reached. The obtained results can have useful implications for research in biomedical applications, especially for anticancer innovative treatments.