Researchers at Iowa State University, with the support of grants from the Office of Naval Research, are using their expertise with the manufacture of microstructures to study and describe the damage to brain cells caused by the formation and collapse of microbubbles — a process known as cavitation.
The researchers report their findings in a paper featured on the cover of the July 2020 issue of the research journal Global Challenges.
Lead authors are Nicole Hashemi, an Iowa State associate professor of mechanical engineering, and Alex Wrede, a former doctoral student and postdoctoral research associate in Hashemi’s lab.
The researchers write that microbubbles measured in microns — that’s millionths of a meter — can form in cerebral spinal fluid inside the skull during traumatic brain injuries.
The researchers wrote the “formation and dramatic collapse” of these microbubbles could be responsible for some of the damage in a brain injury.
Bubble damage may sound trivial. But bubble collapse, and the resulting shock waves, are known to damage the steel foundations of boat propellers.
The researchers report that prior studies indicate the expansion and collapse of microbubbles creates forces of 0.1 to 20 megapascals, or 14.5 to 2,900 pounds per square inch.
” … So it is alarming to realize the damage that cavitation inflicts on vulnerable brain tissue,” the researchers wrote.
To test and characterize the impact of cavitation inside the skull, the researchers simulated a brain by creating a 3D cell culture platform for astrocytic cells (star-shaped cells in the brain and spinal cord that are active in supporting, maintaining and repairing the central nervous system).
They submerged the cell culture platform in a small tank and created microbubbles around 60 millionths of a meter in size. Some of the microbubbles adhered to the cell-laden microfiber scaffold.
Researchers turned on an ultrasonic device in the tank, collapsing the microbubbles and creating cavitation. (They also used the ultrasonic device on a control group of cells that were not exposed to cavitation.)