The blood-brain barrier is composed of tightly fit cells that separate blood vessels from the brain. The barrier protects the brain from bacteria and toxic chemicals. However, it also prevents medicines from effectively reaching the brain. One effective and relatively safe method to open up the blood-brain barrier is ultrasound. Focused ultrasound waves interact with injected microbubbles that expand and contract, temporarily pushing the blood-brain barrier open physically. Non-toxic and biodegradable ultrasound implants would be a convenient way to deliver ultrasound under human skulls. Until recently, such a material did not exist.
Researchers at the University of Connecticut developed a recipe to turn poly L-lactic acid, a biodegradable polymer, into piezoelectric nanofibers. That is, these fibers can change shape when stimulated with electricity. Turning the fibers into a mesh produces a diaphragm that moves with electricity – effectively an ultrasound speaker. The mesh was implanted inside the skull of live mice and connected to a circuit board on the outside with a biodegradable wire. When researchers applied electricity to generate ultrasound, they found that chemical compounds normally found in the bloodstream can make their way inside the brain, proving that the blood-brain barrier could be opened with the device.
The biodegradable implant could be used to facilitate the delivery of drugs into the brain for treatment of depression and brain cancer for example. The device’s safety and effectiveness will need to be tested further in larger animals and on a longer time scale. After all, the blood-brain barrier is there to protect the brain. Disruption of the barrier even temporarily may be harmful, letting in bacteria and other unwanted chemicals along with the medicine. It is also currently unknown whether delivering ultrasound by such device, which requires invasive surgery to implant, is truly superior to applying ultrasound externally using bulkier machines.
Managing Correspondent: Veerasak (Jeep) Srisuknimit
Original Paper: PNAS
Press article: Medical Express
Related SITN articles: Efficient drug delivery platform into the brain
Image Credit: Joe Olmsted