Fig. 1

A schematic diagram representing the various types of nano-systems (NS) that have been used for cancer treatment/diagnosis. NS are presented in a hierarchical order, starting from a backbone consisting of nano-bubbles/nano-droplets, mesoporous nano-complexes, nanocrystals, biological nanostructures, to which one or several functional element(s) is/are added. Such functional elements provide the backbone with a therapeutic, imaging, or targeting activity. In some cases, another radiation than ultrasound can be used, such as laser for PDT/PTT treatment or PA imaging, or a magnetic field to yield magnetic targeting when the backbone is made of metallic elements. A unique feature of these nano-systems, which is not often encountered in nano-systems not excited by ultrasounds, lies in their gaseous content, which can either be used for cancer treatment, e.g. through O₂ release to fight against tumor hypoxia, or for tumor imaging, e.g. by using microbubbles with a different acoustic impedance from that of the tissular environment