Transparent Skull Implant Provides Access to the Brain

The researchers then used current-activated, pressure-assisted densification (CAPAD) to reduce the porosity of the material to nanometric dimensions, thus reducing the optical scattering to turn the nc-YSZ to transparent. The transparent YSZ was then polished, heated, and slow cooled to toughen the material, and cut into rectangular implants of 2.1 x 4.2 x 0.2 mm³.

The researchers then performed right-sided craniectomies on anesthetized mice, fixing the implants to the surrounding skull with dental cement. Using optical coherence tomography (OCT) imaging of the underlying brain, they showed that signal strength was improved when imaging through nc-YSZ implants, relative to the native control calvarium. The researchers added that signal strength at nearly every depth was much higher when imaging through the nc-YSZ implant. The study was published in the September 2013 issue of Nanomedicine: Nanotechnology, Biology and Medicine.

“This is a crucial first step towards an innovative new concept that would provide a clinically-viable means for optically accessing the brain, on-demand, over large areas, and on a chronically-recurring basis, without need for repeated craniectomies,” said study coauthor associate professor of biomedical sciences Kevin Binder, MD, PhD. “Similarly, it may enable chronic monitoring and more precise targeting of photodynamic therapies for residual gliomas, which could prolong survival and improve quality of life for many suffering from brain cancer.”

Transparent cranial implants could serve as a critical enabler for laser-based diagnosis and treatment of many neurological disorders. However, the intrinsic brittleness of current transparent implants predisposes them to catastrophic fracture-based failure, thus limiting opportunity for clinical translation. The new nc-YSZ transparent implants could address this issue since it is a tough ceramic with well-proven biocompatibility in other chronic implantation applications.

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