Humorist Ambrose Bierce once described medicine as a stone thrown down Broadway to kill a dog in the Bowery. Despite its violent metaphor, it captures a long-known fact: we take many medicines into our whole system, as pills or injections, to reach one small infected or cancerous part.
A drug goes to all parts of the body and there can be a lot of collateral damage to some of the healthy parts – as anyone undergoing chemotherapy can testify. There exist strategies to make drug delivery more targeted, such as putting a drug in a tiny fat-membraned body that bears molecules to stick best to the affected place in the body.
Here’s a new one from my alma mater, Caltech which has been long known for engineering and physical science but more recently and increasingly for biomedical science. Yuxing Yao and colleagues reported a clever way to use ultrasound to activate drugs. They put the drugs into tiny gas-filled pockets with membranes made of proteins rather than fats. These circulate in the blood, just like many other medicines. The trick is to focus ultrasound on the tissue where you want the vesicles to break and release the drug. Levels of ultrasound that break the vesicles don’t harm tissues, which don’t absorb significant energy, lacking gas pockets. The gas pockets are just the right size to respond to the chosen ultrasonic frequency.
This has been an outreach activity of the Las Cruces Academy, viewable at GreatSchools.org.
