Earlier this year, scientists made news by embedding a transparent window into the head of a fruit fly to be able to monitor its thoughts. But researchers elsewhere have been working on developing a transparent window to the human brain since 2013. Now two new studies have bolstered the concept's feasibility.

About three years ago, researchers created a skull implant using a material known as yttria-stabilized zirconia, or YSZ – the same substance that's used in ceramic hip implants and dental crowns. Only in this case, the YSZ produced was transparent.

The creation of the implant was part of the "Window to the Brain" project, a multi-institution cross-disciplinary effort to develop a transparent portal that could be embedded in the human skull. Such an advancement would allow doctors to deliver laser-based treatments which have been shown effective in battling brain-based diseases such as cancer or traumatic brain injuries – without having to repeatedly remove the skull each time the therapy is introduced.

Late last year, the initiative – which is a joint effort between two Californian and three Mexican universities – received a total of US$4.6 million in grant money to further the research over the course of five years.

As part of the continuing research, two new studies validate the feasibility of the window.

An artist's impression of how the implant could deliver laser light to where it's needed to treat various conditions in the brain(Credit: UC Riverside)

The first, published July 8 in Lasers in Surgery and Medicine, showed that a window in the skull could not only allow lasers to pass into the brain to combat primary conditions, but that it could also facilitate the use of laser light to blast away bacterial infections, which are common around the site of an implant. In the study, the researchers saw success using lasers beamed through the window to kill E. coli bacteria that was clinging to it, and believe such a procedure could work in vivo, with no damage to the tissue beneath the window.

According to neurosurgeon and neuroscientist Devin Binder from the University of California Riverside (UCR) who's a collaborator on the project, the finding is particularly important because many antibiotics don't penetrate the blood-brain barrier and therefore would be ineffective at eliminating a bacterial infection around the implant.

The second study was recently published online in the journal Nanomedicine: Nanotechnology, Biology and Medicine, and looked at implantation of the YSZ window in a hamster. The goal was to see how well its body accepted the implant. The researchers found that it was tolerated extremely well, with no unusual inflammatory or other immune response.

"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," said Guillermo Aguilar, professor of mechanical engineering in UCR's Bourns College of Engineering. Aguilar leads the Window to the Brain project with Santiago Camacho-López, from the Centro de Investigación Científica y de Educación Superior de Ensenada (CICESE) in Mexico.

Going forward, the Window to the Brain team will be using their recent funding to investigate new materials that could toughen the implant as well as better ways in which to shape it. They will also be looking at how lasers react as they pass through different materials and will continue to see how the implant responds in animal studies.

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