Drug-mediated acoustic reporter genes for mammalian cell ultrasound imaging

The newly established field of genetically encoded ultrasound contrast agents in the form of gas vesicles could expand the uses of medical ultrasound imaging for cell specific deep tissue imaging. However, current gene constructs encoding for these gas vesicles require significant cell processing to ensure sufficient gas vesicles are formed within the cell to produce ultrasound contrast. Here, we describe a drug-inducible and drug-selectable acoustic reporter gene construct that can enable gas vesicle expression in mammalian cell lines, which we demonstrate in wild type HEK293T cells. Plasmid integration was validated using fluorescence microscopy, and flow cytometry was used to establish single cell clones of the cells. Gas vesicle expression was optically and ultrasonically verified, with an 80% improved signal to noise ratio in cells expressing gas vesicles compared to negative controls. This technology presents a new reporter gene paradigm by which ultrasound can be harnessed to visualize specific cell types in vitro and invivo for various applications, including cellular reporting and cell therapies.