Event Abstract

Biocompatibility and electrochemical assessment of boron doped nanocrystalline diamond electrodes for neural stimulation

  • 1 Aalborg University, Dept. of Health Science and Technology, Denmark
  • 2 Aalborg University, Dept. of Health Science and Technology, Denmark
  • 3 ASCR, Institute of Physics, Czechia
  • 4 NANO6, Czechia
  • 5 University Hasselt, IMEC, Belgium

Neural prostheses are devices that use electrical impulses to restore sensory or motor deficits following trauma or neurological diseases. In implanted devices, electrodes located in close proximity to the neural tissue are in charge of delivering the electrical impulses generated in a stimulation unit. The electrodes for neural stimulation possess one or various contact sites comprising a metal, such as platinum or iridium oxide, or a ceramic, such as titanium nitride (TiN). Although these are non-toxic materials with excellent electrochemical properties, many of the currently used designs display a compromised long-term performance as a result of the foreign body reaction. The growth of encapsulation tissue around the contact sites increases the distance between the electrode and neural cells over time. As a consequence, it is necessary to inject larger currents in order to achieve cell activation, which might exceed the potential at which oxidation and reduction of water takes place causing irreversible damage to the electrode and tissue. In recent years, nanocrystalline diamond (NCD) films have emerged as a unique class of biomaterials, which hold promise for the fabrication of neural electrodes due to their chemical inertness, biocompatibility and outstanding electrical properties (Pennisi and Alcaide, 2014). In this talk, a series of studies assessing the biocompatibility and electrochemical performance of boron doped NCD films for application in neural stimulation electrodes is described. The fabrication of boron doped NCD test substrates and electrodes by microwave chemical vapor deposition is presented. Furthermore, surface characterization of these substrates by Raman spectroscopy and atomic force microscopy is shown. Results of in vitro studies using the test substrates comprise protein adsorption, cytotoxicity, and cell proliferation and adhesion assays. These results are presented to describe the effects of the surface properties of the NCD films on the biological responses. We demonstrate that an increased surface roughness is crucial to significantly reduce adhesion and proliferation of fibroblasts on the NCD surfaces (Alcaide et al., 2014). The electrochemical performance and the in vivo biocompatibility of the boron doped NCD films are assessed using monopolar electrodes. It is shown that while electrical parameters such as impedance and charge injection capacity are similar to that of control TiN electrodes, NCD electrodes display a much wider water potential window, ranging from -1.7 to 1.4 V (Meijs et al.,2013). Data from the in vivo biocompatibility studies is also analyzed, consisting on the histological and histomorphometric assessment of the fibrous capsule after 2 and 4 weeks of subcutaneous implantation in a rat model. We show that implantation of NCD electrodes is associated with no signs of chronic inflammation and a very thin fibrous capsule, which after two weeks of implantation exhibit an average thickness of 25 μm. In summary, this talk presents data demonstrating that the proposed boron doped NCD electrodes can be safely operated within a wide potential window and cause a minimal foreign body reaction upon implantation. Taken together, these results indicate that boron doped NCD films represent a promising approach to mitigate the issues associated with fibrous encapsulation of neural stimulation electrodes

Acknowledgements

This work was supported by the EU through the project MERIDIAN (Micro and Nano Engineered Bi-Directional Carbon Interfaces for Advanced Peripheral Nervous System Prosthetics and Hybrid Bionics), contract n. 280778-02.

References

1. Pennisi, C. P., and Alcaide, M. (2014). “Nanocrystalline diamond films for biomedical applications,” in The Design, Synthetic Strategies and Biocompatibility of Polymer Scaffolds for Biomedical Application, ed. S. Cao, and H. Zhu (Bentham Science Publishers), 70-100.

2. Alcaide M., Taylor A., Zachar V., and Pennisi C.P. (2014). Control of fibroblast growth on nanocrystalline diamond films: The effect of topography. Proceedings of the 7th Annual Meeting of the Scandinavian Society of Biomaterials, April 2014, Aarhus, Denmark. Eur Cell Mater (Suppl) in press.

3. Meijs, S., Taylor, A., Pennisi, C. P., and Rijkhoff, N. (2013). Electrochemical characterization of boron-doped nanocrystalline diamond electrodes for neural stimulation. Abstract from International IEEE EMBS Conference on Neural Engineering, San Diego, CA, USA.

Keywords: nanocrystalline diamond, neuroprosthetic interfaces, Electrical Stimulation, Biocompatibility, neural electrodes

Conference: MERIDIAN 30M Workshop, Brixen, Italy, 25 Sep - 25 Sep, 2014.

Presentation Type: Oral Presentation

Topic: Neuroengineering

Citation: Pennisi CP, Alcaide M, Papaioannou S, Meijs S, Taylor A, Nesladek M and Zachar V (2014). Biocompatibility and electrochemical assessment of boron doped nanocrystalline diamond electrodes for neural stimulation. Front. Neuroeng. Conference Abstract: MERIDIAN 30M Workshop. doi: 10.3389/conf.fneng.2014.11.00005

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Received: 06 Nov 2014; Published Online: 06 Nov 2014.

* Correspondence: Dr. Cristian P Pennisi, Aalborg University, Dept. of Health Science and Technology, Aalborg, Denmark, cpennisi@hst.aau.dk

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