Conventional microcrystalline YSZ has been used for decades as a implant material (e.g. dental crowns and femoral caps for total hip replacement), due to its combination of biocompatibility and mechanical toughness (greater than that of bone). While its biocompatibility has been widely studied, the nanocrystalline structure of our YSZ must be independently confirmed. For example, nanoscale materials have a much greater surface area to volume ratio, making them more reactive than bulk counterparts. Further, the micro- and nano-scale surface texture can have a significant impact on how cells respond to the material. For our application, we are most interested in the response of fibroblasts and osteocytes, as these are the cell types which are likely to come into contact with the WttB implant. Osteo-integration with the skull is desired, as well as a minimal fibrotic response.
To assess these biological responses to the various compositions of our WttB implant, we are conducting in vitro cytocompatibility studies in mesenchymal bone marrow stem cell cultures and fibroblast cultures.
Further, while we have previously confirmed biocompatibility of the nanocrystalline transparent YSZ in vivo, we have not yet assessed the tolerance in the cranial environment specifically. Implants in various parts of the body can result in significantly different biological responses. In addition to the tolerance of the cranial implant by the host organism (mouse), we will also be assessing how the anticipated fibrotic response affects the transparency of the implant, and methods to control and/or mitigate this fibrotic deposition.