Scheme 1

Schematics of the US-activated prodrug-loaded liposome (CPBSN38L) and its delivery process for cancer-targeting therapy. A The composition, preparation, and transformability of CPBSN38L. B Chemical structure of the prodrug PBSN38 and Ce6- and US irradiation-induced activation of this prodrug. C After being administered through intravenous injection (1), CPBSN38L circulates stably in the bloodstream (2), accumulates in the tumor because of both the enhanced permeability and retention effect and transcytosis (3), and is internalized into the tumor cells (4). After US irradiation, the sonosensitizer Ce6 produces large amounts of intracellular reactive oxygen species to trigger PBSN38 activation and release of the active SN38 (5). The free SN38 induces cell apoptosis, thereby triggering strong anticancer activity in the murine tumor models of colon adenocarcinoma or hepatocellular carcinoma (6)