Nowadays, recurrence of the primary tumor affects a relatively high number of patients, because of the not complete remission of the tumor by the treatment: the minimal residual disease (MRD) continues its activity, initiating relapse and metastasis. Thus, further treatments must be introduced, causing additional health issues on patients and requiring much higher costs. Cancer’s progression, recurrence and metastasis mostly occurs by means of circulating tumor cells (CTCs): they belong to the primary tumor and become able to leave it and diffuse through the bloodstream, forming new tumors (metastases) in distant tissues and organs. The XtraUS project, whose initial steps are represented by this Master Thesis, aims to prevent cancer relapse and metastasis by developing a breakthrough technology against CTCs: the novel idea introduced by this technology is an extracorporeal set – up (cartridge) along which blood circulates, where an innovative stimuli-responsive, targeted and non-immunogenic nanoconstruct is injected and activated by ultrasounds (US) to act against flowing CTCs in the blood.