Remote control of chemical reactions in biological environments could enable a diverse range of medical applications. The ability to release chemotherapy drugs on target in the body, for example, could help bypass the damaging side effects associated with these toxic compounds. With this aim, researchers at California Institute of Technology (Caltech) have created an entirely new drug-delivery system that uses ultrasound to release diagnostic or therapeutic compounds precisely when and where they are needed.
The platform, developed in the labs of Maxwell Robb and Mikhail Shapiro, is based around force-sensitive molecules known as mechanophores that undergo chemical changes when subjected to physical force and release smaller cargo molecules. The mechanical stimulus can be provided via focused ultrasound (FUS), which penetrates deep into biological tissues and can be applied with submillimetre precision. Earlier studies on this method, however, required high acoustic intensities that cause heating and could damage nearby tissue.
To enable the use of lower – and safer – ultrasound intensities, the researchers turned to gas vesicles (GVs), air-filled protein nanostructures that can be used as ultrasound contrast agents. They hypothesized that the GVs could function as acousto-mechanical transducers to focus the ultrasound energy: when exposed to FUS, the GVs undergo cavitation with the resulting energy activating the mechanophore.
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