RIVERSIDE, Calif. — Use of a novel material, nanocrystalline yttria-stabilized zirconia (nc-YSZ), to make cranial implants may allow the safe and efficacious use of laser-based therapies to treat brain disorders and combat the bacterial infections that are a leading cause of cranial implant failure. Nc-YSZ is a transparent version of the same ceramic that is used to make dental crowns and hip implants. 

Known as Window to the Brain (WttB), an implant made with nc-YSZ could improve patient care by providing a way to both deliver and collect light to and from the brain, on demand, over large areas, and on a recurring basis without the need for repeated craniotomies. Nc-YSZ was developed by professor Guillermo Aguilar and his team at the University of California, Riverside (UCR). 

This is an illustration showing how the "Window to the Brain" transparent skull implant created by UC Riverside researchers would work. Courtesy of UC Riverside.

In its most recent study, the research team at UCR demonstrated that when a culture of E. coli was seeded between an nc-YSZ implant and an agar plate and irradiated using NIR laser treatment, the E. coli biofilm formation across the thickness of the implant was reduced. The results of the experiment suggest that using nc-YSZ for a cranial implant in vivo may allow for use of lasers to provide selective, noninvasive, chronic treatment of bacterial layers that form under cranial implants, without causing adverse thermal damage to the underlying host tissue when using appropriate laser parameters. 

"This was an important finding because it showed that the combination of our transparent implant and laser-based therapies enables us to treat not only brain disorders, but also to tackle bacterial infections that are common after cranial implants. These infections are especially challenging to treat because many antibiotics do not penetrate the blood brain barrier," said Devin Binder, M.D., a neurosurgeon and neuroscientist in UCR's School of Medicine. 

Another study explored the biocompatibility of YSZ in an animal model, where it integrated into the host tissue without causing an immune response or other adverse effects. 

"The YSZ was actually found to be more biocompatible than currently available materials, such as titanium or thermo-plastic polymers, so this was another piece of good news in our development of transparent YSZ as the material of choice for cranial implants," Aguilar said. 

The use of nc YSZ to create Window to the Brain implants has the potential for enhancing light-based diagnosis and treatment of a wide variety of brain pathologies including cerebral edema, traumatic brain injury, stroke, glioma and neurodegenerative diseases. The research team's long-term goal is to see the technology become the standard of care for patients with brain disorders who would benefit from laser-based treatments. 

The Window to the Brain project is a multi-institution, interdisciplinary partnership led by Guillermo Aguilar, professor of mechanical engineering in UCR's Bourns College of Engineering, and Santiago Camacho-López, from the Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE) in Mexico. 

The research was published in Lasers in Surgery and Medicine (doi: 10.1002/lsm.22558) and Nanomedicine: Nanotechnology, Biology and Medicine (doi:10.1016/j.nano.2016.04.009).