Short Communication
Transparent nanocrystalline yttria-stabilized-zirconia calvarium prosthesis

https://doi.org/10.1016/j.nano.2013.08.002 Get rights and content

Abstract

Laser-based diagnostics and therapeutics show promise for many neurological disorders. However, the poor transparency of cranial bone (calvaria) limits the spatial resolution and interaction depth that can be achieved, thus constraining opportunity in this regard. Herein, we report preliminary results from efforts seeking to address this limitation through use of novel transparent cranial implants made from nanocrystalline yttria-stabilized zirconia (nc-YSZ). Using optical coherence tomography (OCT) imaging of underlying brain in an acute murine model, we show that signal strength is improved when imaging through nc-YSZ implants relative to native cranium. As such, this provides initial evidence supporting the feasibility of nc-YSZ as a transparent cranial implant material. Furthermore, it represents a crucial first step towards realization of an innovative new concept we are developing, which seeks to eventually 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.

From the Clinical Editor

In this study, transparent nanocrystalline yttria-stabilized-zirconia is used as an experimental “cranium prosthesis” material, enabling the replacement of segments of cranial bone with a material that allows for optical access to the brain on a recurrent basis using optical imaging methods such as OCT.

Graphical Abstract

Transparent cranial implants could serve as a critical enabler for laser-based diagnosis and treatment of many neurological disorders. However, the intrinsic brittleness of transparent implants reported thus far predisposes them to catastrophic fracture-based failure, thus limiting opportunity for clinical translation. Novel nanocrystalline transparent implants are reported herein that seek to address this limitation through use of zirconia, a tough ceramic with well-proven biocompatibility in other chronic implantation applications.

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Section snippets

Methods

The transparent nc-YSZ cranial implants were made possible through use of the CAPAD process,9 an emerging technique that enables reduction of internal porosity to nanometric dimensions, and thus, reduction of the optical scattering that renders typical YSZ opaque.10 Densified nc-YSZ blanks were polished, annealed, and machined into rectangular implants with dimensions of 2.1 × 4.2 × 0.2 mm3. Figure 1, A demonstrates the transparency of the finished implants.

As shown in Figures 1, B-D, right-sided

Results

Figure 2 shows cross-sectional OCT images of murine brain through native cranium (left of midline) and nc-YSZ implant (right of midline) in the same animal. Detailed description of the image interpretation is presented in the Supplemental Materials. The enhanced transparency of the nc-YSZ implant is evidenced by the opportunity it provides for imaging of sub-cortical white matter (darker band at bottom of image, right of midline), which is nearly imperceptible when imaging through native

Discussion

Figure 2, Figure 3 demonstrate that OCT imaging through nc-YSZ implants is indeed possible and provides greater signal strength than imaging through native cranium. This, therefore, establishes the initial feasibility of nc-YSZ as a transparent cranial implant material for optical diagnostic and therapeutic applications. Moreover, when coupled with the high toughness of nc-YSZ, this suggests unique potential for eventual clinical application.

However, before such potential can be realized,

Acknowledgments

The authors thank Ms. Melissa Eberle for her contribution to OCT data collection, and Prof. Elaine Haberer and Mr. Mohammad Shahriar Zaman for their contribution to nc-YSZ absorption characterization.

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Cited by (0)

Research Support: This research was supported, in part, by the University of California, Riverside Chancellor's Strategic Research Initiative (PI: G. Aguilar).

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