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
