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. 2022 Mar 18;20:139. doi: 10.1186/s12951-022-01243-w

Fig. 1.

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