Ultrasound Microbubbles: A Revolution in Medical Treatment

A significant breakthrough study has showcased the ability to control ultrasound-driven microbubbles within the brain’s blood vessels. This innovative technique offers a focused, minimally invasive method to address brain diseases, including tumors and mental health disorders, potentially minimizing the adverse effects typically associated with drugs. Source: SciTechPost.com

Researchers from ETH Zurich have successfully demonstrated, for the first time, the steering of microvehicles through brain blood vessels in mice using ultrasound. This advancement opens the door to the precise delivery of medications.

The team at ETH Zurich has developed a technique over recent years to maneuver microvehicles using ultrasound, now proven effective in the brain. These microvehicles, essentially harmless gas bubbles that dissolve post-mission, could in the future carry drugs directly to targeted brain areas, enhancing drug effectiveness and reducing side effects.

Treating conditions such as brain tumors, hemorrhages, and various neurological and psychological issues is challenging with medication, often leading to significant side effects due to the drugs affecting the entire brain. With this new research, there’s optimism for a more localized drug delivery system, employing mini-transporters navigable through the brain’s intricate network of blood vessels.

The collaboration of ETH Zurich, the University of Zurich, and the University Hospital Zurich marks the first instance of guiding microvehicles through an animal’s brain vessels via ultrasound.

The brain’s complex blood supply makes this a challenging endeavor. Credit: Science Photo Library / Francis Leroy

Ultrasound vs. Magnetism

Ultrasound, compared to magnetic field-based navigation, offers notable advantages. Professor Daniel Ahmed of ETH Zurich, a leading figure in the study, notes ultrasound’s safety and deep body penetration as significant benefits.

For this purpose, Ahmed and his team utilized lipid-coated, gas-filled microbubbles, mirroring biological cell membranes. These microbubbles, about 1.5 micrometers in diameter, are already employed in ultrasound imaging as contrast agents.

Benefits of Ultrasound-Controlled Microbubbles

These microbubbles can navigate through blood vessels, as demonstrated by the researchers. “These vesicles, already approved for human use, likely mean our technology will gain approval and application in human treatments faster than other developing microvehicles,” Ahmed states, having received a Starting Grant from the European Research Council ERC in 2019 for this project.

Imagery of brain blood vessels with microvehicle clusters in orange (microscopy image). Credit: Del Campo Fonseca et al., Nature Communications 2023, edited by ETH Zurich

Another advantage is the microbubbles’ dissolution in the body after completing their task. In contrast, magnetic navigation requires biodegradable magnetic microvehicles, which are challenging to develop. The ETH Zurich team’s microbubbles are small and smooth, aiding in their navigation through narrow capillaries, as explained by Alexia Del Campo Fonseca, a doctoral student in Ahmed’s group and the study’s lead author.

Navigating Against Blood Flow

Ahmed and his team have spent years in the lab developing this microbubble navigation method. Collaborating with the University of Zurich and University Hospital Zurich, they’ve now successfully tested it in mouse brain vessels. The injected microbubbles naturally flow with the bloodstream, but the team used ultrasound to control and direct them against the blood flow, even through complex vascular paths.

Controlling the microvehicles involved attaching transducers to the mouse skulls, generating ultrasonic vibrations. These vibrations interact in the brain, amplifying or cancelling each other at specific points. The team used a sophisticated technique to adjust each transducer’s output, monitored through real-time imaging.

Looking Ahead

For imaging in this study, two-photon microscopy was used. Future plans include enhancing ultrasound technology for this purpose.

In this research phase, the microbubbles were not drug-laden. The objective was to establish their navigability in blood vessels and suitability for brain applications. Promising medical applications lie ahead, particularly in cancer, stroke, and mental health treatment. The next phase involves attaching drug molecules to the bubbles for transportation, aiming to develop a method applicable to human treatments.

Reference: “Ultrasound trapping and navigation of microrobots in the mouse brain vasculature” by Alexia Del Campo Fonseca, Chaim Glück, Jeanne Droux, Yann Ferry, Carole Frei, Susanne Wegener, Bruno Weber, Mohamad El Amki and Daniel Ahmed, 21 September 2023, Nature Communications.
DOI: 10.1038/s41467-023-41557-3

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More about ultrasound microbubbles

• Ultrasound Microbubbles in Medical Treatment
• ETH Zurich Ultrasound Research
• Nature Communications Study on Ultrasound Microbubbles
• Ultrasound Technology in Brain Health
• Ultrasound vs. Magnetism in Microbubble Navigation