On-Demand Drug Release under Ultrasound Irradiation

Achieving precise, on-demand release of therapeutic agents remains a central challenge in pharmacology and chemical biology. In this work, we reported a modular prodrug release platform that employed low-intensity medical ultrasound (1 MHz, 2.5 W cm–2) to trigger the cleavage of carbamate and thiocarbamate linkers in aqueous media, enabling on-demand release of hydrophilic drug payloads. The linker was designed to couple drug release with the concurrent release of methylene blue (MB), allowing fluorescence measurements to track ultrasound-triggered linker cleavage and cargo release from the same molecular construct. Mechanistic studies including radical probes, EPR spectroscopy, Fenton validation, and intracellular DCFH-DA imaging supported the crucial role of cavitation-generated •OH and O2•– for the cleavage of the linkers. Furthermore, we evaluated payload compatibility using topotecan (TPT), an FDA-approved anticancer drug, and N-acetyl-l-cysteine as representative hydroxyl- and thiol-containing prodrugs, respectively. Ultrasound irradiation triggered TPT release and restored the cytotoxic activity of the masked prodrug in HeLa cells, whereas the nonactivated prodrug maintained >86% MCF-10A cell viability. Ex vivo studies also showed that ultrasound-triggered MB and TPT release remained detectable through porcine tissue barriers of 2.0 cm thickness, enabling controlled drug release with fluorescence-based monitoring and tissue-penetrating delivery.