Fighting cancer relapse with remote activation of smart and targeted nanoconstructs

One of the major concerns that arises after the overt tumor regression in a patient is the cancer recurrence. The work of this Master thesis takes part in the European project XtraUS, aimed at developing targeted, non-immunogenic, stimuli-responsive nanoconstructs in combination with an extracorporeal bloodstream set-up to eliminate circulating tumor cells (CTCs), responsible for cancer relapse and metastasis spreading. As an initial analysis, the research relies on the effect of the external stimulation on nanoconstructs. For this purpose, an ultrasound stimulation is used together with ZnO nanoparticles, able to enhance the acoustic cavitation phenomenon by introducing a higher amount of gas bubbles in liquids. Thanks to the sinusoidal behavior of the acoustic field, the microbubbles are forced to oscillate, alternating expansion and contraction phases, which may end up in the collapse of gas bubbles. This process is accompanied by a huge release of energy, in terms of temperature and pressure, generating toxic species (Reactive Oxygen Species - ROS), capable to kill CTCs in the blood stream. Two different techniques are exploited to detect the production and concentration of toxic species; the first one is based on the sonochemiluminescence (SCL) of Luminol solutions, which provides a more qualitative but faster analysis. In fact, Luminol molecules, activated with the presence of an oxidant as hydrogen peroxide (H2O2) and hydroxide ions (OH−), are able to emit blue visible light as they chemically react with ROS, allowing their detection merely via a photocamera, in a dark environment. Differently, the second technique relies on the Electron Paramagnetic Resonance Spectroscopy (EPR), based on the interaction between a magnetic field produced by the EPR equipment and the unpaired electrons associated to ROS. As a consequence, this last technique offers a more quantitative and reliable analysis on the concentration of toxic species. Proceeding with these methods, it is possible to investigate the limiting conditions in which ultrasound frequency and power combined with nanoparticles are cytotoxic for cancer cells, without damaging the healthy ones. Upon finding this range of effectiveness, the project is carried on testing the behavior of mere ZnO nanoparticles or functionalized with amino groups, analyzing also their effect on living cancer cells. Furthermore, in order to investigate their behavior in a dynamic condition, the design of a specific cartridge, along with its fabrication, is performed. Therefore, by using a peristaltic pump, it is possible to simulate a situation closer to the real one: the blood stream. Finally, the experimental results are supported and compared to both laminar fluid flow and acoustic pressure simulations performed with COMSOL Multiphysics, providing a better understanding of the physics behind the fluid circulation in the cartridge and sound waves propagation, highlighting their correlation with different channels geometries. Since this Master thesis is inserted in the XtraUS European project, it aims at developing the findings previously achieved on the same work, and, at the same time, at exploring new possible paths to lay the foundations for the evolution of the research.