Laminin Adsorption and Adhesion of Neurons and Glial Cells on Carbon Implanted Titania Nanotube Scaffolds for Neural Implant Applications

As the world's population ages, the incidence of neurodegenerative disorders such as Parkinson's disease inevitably increases. Currently, brain-machine interfaces are used to study these diseases<i> ex vivo</i>, while neural electrodes are employed to treat them symptomatically <i>in vivo</i>. However, numerous obstacles arise at the interface between the brain and the brain-machine interface. Long-term adhesion is often weak, and rejection reactions such as glial scarring occur. We demonstrate that ion-implanted titania nanotube scaffolds are a promising candidate to overcome these problems, as they combine high biocompatibility with appropriate electrical conductivity.<br/>In our systematic study, we show how implantation-induced tube shrinkage and altered electrical conductivity of titania nanotube scaffolds influence protein adsorption kinetics. Interestingly, laminin adsorption is affected by changes in surface free energy upon implantation. An increase in the pH-dependent ζ-potential of the surfaces leads to changes of the laminin binding.<br/>In addition, viability, toxicity and morphology of U87MG glial cells and differentiated SH-SY5Y neurons is analyzed after one and four days, respectively, and correlated with surface characteristics. Environmental electron microscope images reveal that cells on all scaffolds stretch out and expand even after one day. This first evidence of biocompatibility is confirmed by a high cell viability. Significant differences of cell viability are explained by changes of protein adsorption induced by ion implantation. Additionally, the increase in conductivity does not affect neuronal viability after four days but inhibits glial cell proliferation.<br/>Based on these findings, there is great potential for novel neural electrode materials with tailored morphology and unique conductivity that suppress glial scar formation.<br/>We gratefully acknowledge funding from the Saxon State Ministry for Higher Education, Research and the Arts, project MUDIplex, grant number 100331694.<br/>[1] Frenzel, Jan, et al. "Laminin Adsorption and Adhesion of Neurons and Glial Cells on Carbon Implanted Titania Nanotube Scaffolds for Neural Implant Applications." <i>Nanomaterials</i> 12.21 (2022): 3858.