Microbubble bots guided through complex brain vessels using ultrasound

Researchers have developed a bubble microrobot capable of being guided around the tiny complex blood vessels of the brain using ultrasound. Successfully tested in mice, the ‘microvehicle’ holds potential as a means of precisely delivering drugs to treat diseases like brain cancer and stroke.

Researchers at ETH Zurich, the University of Zurich and University Hospital Zurich have collaborated to develop microvehicles – gas-filled microbubbles coated in lipids – that can navigate the narrow and complex blood vessels of a mouse brain using ultrasound.

“In addition to being widely used in the medical field, ultrasound is safe and penetrates deep into the body,” said Daniel Ahmed, one of the study’s corresponding authors.

The small, smooth, gas-filled microbubbles, which have a diameter of between 1.1 and 1.4 µm, were made of a fluorescent contrast agent currently used in ultrasound imaging. They dissolve in the body over time and the lipid shell is made from the same substance that biological cell membranes are made of.

The researchers injected the microbubbles into mice and allowed them to circulate in the animal’s bloodstream. Microscopy allowed real-time imaging of the bot. Using up to four ultrasound-generating transducers attached to the outside of the mouse’s head, the researchers found that the microbots responded to the acoustic waves by self-assembling into swarms and navigating along the brain vasculature.

Image source: Del Campo Fonseca et al. (2023), Nature Communications.