Electrochemical properties of titanium nitride nerve stimulation electrodes: an in vitro and in vivo study

Abstract

The in vivo electrochemical behavior of titanium nitride (TiN) nerve stimulation electrodes was compared to their in vitro behavior for a period of 90 days. Ten electrodes were implanted in two Göttingen minipigs. Four of these were used for electrical stimulation and electrochemical measurements. Five electrodes were kept in Ringer's solution at 37.5°C, of which four were used for electrical stimulation and electrochemical measurements. The voltage transients measured in vivo were 13 times greater than in vitro at implantation and they continued to increase with time. The electrochemical properties in vivo and the tissue resistance (Rtissue) followed a similar trend with time. There was no consistent significant difference between the electrochemical properties of the in vivo and in vitro electrodes after the implanted period. The differences between the in vivo and in vitro electrodes during the implanted period show that the evaluation of electrochemical performance of implantable stimulation electrodes cannot be substituted with in vitro measurements. After the implanted period, however, the performance of the in vivo and in vitro electrodes in saline was similar. In addition, the changes observed over time during the post-implantation period regarding the electrochemical properties of the in vivo electrodes and Rtissue were similar, which indicates that these changes are due to the foreign body response to implantation.

Nanotopographical Coatings Induce an Early Phenotype-Specific Response of Primary Material-Resident M1 and M2 Macrophages

“…However, this beneficial property regarding cell adhesion and protein adsorption appeared to be independent of the diameter, and length of the nanotubes, respectively. The increased intensity of the anatase peak in the X-ray diffraction pattern recorded for rising anodization voltages, as well as the simultaneously observable decline of the Ti signal, that was associated with the remaining underlying coating, can be attributed to an increasing thickness of the NT array with rising voltage, an effect that could also be observed at the anodization of bulk titanium [35]. A typical finding in the diffraction patterns of NT arrays annealed at 450 • C is also the observed phase mixture with a high ratio of anatase to rutile [42].…”

“…TiN has a long history in the field of biomaterials, and its various forms have found applications ranging from protective coatings for orthopedic implants to electrodes for nerve stimulation or pacemakers [31][32][33]. Although, there is literature that investigates the in vivo encapsulation of TiN showing a fractal nanotopography, but focused on the inflicted change of electrical parameters due to the fibrous encapsulation, there are no studies that investigate the response of macrophages to this kind of surface structure, and thus, it represents an interesting opportunity for extending the scope of this study and verifying a subtype-specific response of macrophages to nanostructured surfaces [34,35].…”

Diamond/Porous Titanium Nitride Electrodes With Superior Electrochemical Performance for Neural Interfacing

“…Titanium nitride (TiN) is an attractive material, which can be applied for the fabrication of porous templates with high electrochemical surface area (ESA) by simple physical vapor deposition techniques. Porous TiN coatings have long been employed for pacemaker electrodes and have also been used for fabrication of neural stimulation and recording electrodes (Norlin et al, 2005 ; Specht et al, 2006 ; Meijs et al, 2015a ). The porosity of TiN films can be easily controlled by adjusting the deposition parameters, such as gas composition, flow rate, and deposition time (Norlin et al, 2005 ; Cunha et al, 2009 ).…”

Increased Charge Storage Capacity of Titanium Nitride Electrodes by Deposition of Boron-doped Nanocrystalline Diamond Films

“…An increased amount of nitrogen in the coating, however, also results in increased dissolution rates and oxide thickness when high anodic potentials are reached (Cunha, 2009). In addition, higher potentials were observed when applying stimulation pulses using implanted TiN electrodes (Meijs, 2015), which may compromise safety during electrical stimulation. It is thus advantageous to apply an additional coating to improve the corrosion resistance and in vivo electrochemical properties.…”