Even though the number of ways doctors can fight cancer is rapidly increasing, traditional chemotherapy is still widely used to combat tumors. In fact, according to a study in The Lancet Oncology, it is predicted that the number of people needing the treatment is set to increase by 53% between 2018 and 2040. But many of the well-known issues with chemotherapy still exist: it can cause hair loss, nausea, weight loss, anemia, peripheral neuropathy, and more. Plus, because chemo drugs treat the whole body, they can cause damage to cells outside of the intended tumor targets.

Attempting to make chemotherapy a more targeted solution, researchers in 2020 combined cancer-fighting chemicals with bursts of laser light to activate them at tumor sites. While that treatment shows promise, its efficacy is limited to a few millimeters below the skin, which is the maximum depth a laser beam can penetrate in order to activate the chemicals.

Seeking to harness the power of the targeted activation of chemotherapeutic drugs but increase the depths at which they can function, scientists at the City University of Hong Kong (CityU) turned to the idea of using soundwaves.

Working with cancer cell cultures in their lab, the researchers created a small-molecule platinum-based prodrug called cyaninplatin, which gathered at the tumor sites. Prodrugs are compounds that are inert until they are activated inside the body. They then beamed the cyaninplatin with highly-targeted ultrasound waves, which converted it to carboplatin, a common chemotherapy drug. This induced tumor death by damaging the mitochondria inside the cancer cells.

The method was able to reduce cancer cell viability by 51% when tissue coverage was 1 cm thick (about 0.4 in) and 33% with tissue coverage at a thickness of 2 cm.