Neurobiochemical changes in the vicinity of a nanostructured neural implant

Neural interface technologies including recording and stimulation electrodes are currently in the early phase of clinical trials aiming to help patients with spinal cord injuries, degenerative disorders, strokes interrupting descending motor pathways, or limb amputations. Their lifetime is of key importance; however, it is limited by the foreign body response of the tissue causing the loss of neurons and a reactive astrogliosis around the implant surface. Improving the biocompatibility of implant surfaces, especially promoting neuronal attachment and regeneration is therefore essential. In our work, bioactive properties of implanted black polySi nanostructured surfaces (520–800 nm long nanopillars with a diameter of 150–200 nm) were investigated and compared to microstructured Si surfaces in eightweek- long in vivo experiments. Glial encapsulation and local neuronal cell loss were characterised using GFAP and NeuN immunostaining respectively, followed by systematic image analysis. Regarding the severity of gliosis, no significant difference was observed in the vicinity of the different implant surfaces, however, the number of surviving neurons close to the nanostructured surface was higher than that of the microstructured ones. Our results imply that the functionality of implanted microelectrodes covered by Si nanopillars may lead to improved long-term recordings

Attachment of Primary Mouse Astroglial Cells on Neural Implant Surfaces

In vitro micro- and nanofabricated test chips were used to investigate mouse primary cortical astroglial cell reactions to different surfaces of a multichannel neural microelectrode implant. The following surface types were fabricated by MEMS technology and characterized by scanning electron microscopy: poly-Si, Pt, nanostructured Si and nanostructured Pt. Survival of primary cortical mouse astroglial cells was analysed by fluorescent microscopy 24 hours after seeding. Our results show that the nanostructured surfaces are not toxic to the primary mouse astroglial cells

In Vivo Iontophoretic BDA Injection through a Buried Microfluidic Channel of a Neural Multielectrode

AbstractThis paper presents in vivo local iontophoretic release of a neuronal tracer, biotinylated dextran amine (BDA) in the rat brain using monolithically integrated microfluidic channel buried in a neural multielectrode. The tracer injection is controlled by iontophoresis using Pt electrodes in the vicinity of the outlet of the microfluidic channel. The successful injection is evaluated through histological maps of the labelled nerve cells in 3D. Together with previous electrophysiological studies we conclude that the presented device is capable of simultaneous in vivo multichannel neural recording and controlled tracer injection for mapping neuronal pathways of the brain

Modification of Glial Attachment by Surface Nanostructuring of SU-8 Thin Films

Various methods are currently under development to enhance the biocompatibility of neural electrodes and to minimize the reactive gliosis around the implant surface. As cells in their native microenvironment interact with 3D nanoscale topographies of the extracellular matrix, physical modification of implant surfaces may provide an alternative solution to the negative tissue response by imitating the structure of the extracellular matrix, and therefore affecting the attachment and behavior of neurons and glial cells. The attachment of primary mouse astrocytes on nanostructured SU8 polymer surfaces fabricated by e-beam lithography was investigated in our study. We found that attachment of primary mouse astrocytes on silicon-SU8 surfaces is strongly influenced by the surface topography