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Abstract: We compared porous silicon (pSi) with smooth Si as chip-implant surfaces in a nerve regeneration setting. Silicon chips can be used for recording neural activity and are potential nerve interface devices. A silicon chip with one smooth and one porous side inserted into a tube was used to bridge a 5 mm defect in rat sciatic nerve. Six or 12 weeks later, new nerve structures surrounded by a perineurium-like capsule had formed on each side of the chip. The number of regenerated nerve fibers did not differ on either side of the chip as shown by immunostaining for neurofilaments. However, the capsule that had formed in contact with the chip was significantly thinner on the porous side than on the smooth side. Cellular protrusions had formed on the pSi side and the regenerated nerve tissue was found to attach firmly to this surface, while the tissue was hardly attached to the smooth silicon surface. We conclude that a pSi surface, due to its large surface area, diminished inflammatory response and firm adhesion to the tissue, should be a good material for the development of new implantable electronic nerve devices. [Copyright &y& Elsevier]

Axonal growth and guidance were studied on different micro- and nanostructured surfaces. Nanoimprinted grooves in a polymer, epitaxial III/V nanowires, porous silicon patterns, and chemically altered surfaces were all shown to induce axonal guidance. Neurons were also found to be able to attach and grow on gallium phosphide nanowires without compromising cell survival. The results are important for the construction of a new generation of neuroelectrical interfaces, including high spatial resolution electrodes. The advantages of the different nanostructured surfaces are discussed. [ABSTRACT FROM AUTHOR]

Axonal outgrowth on smooth and porous silicon surfaces was studied in organ culture. The pore size of the silicon substrata varied between 100 and 1500 nm. We found that axons preferred to grow and elongate on porous silicon surfaces only when pores of (150-500 nm) are available. [ABSTRACT FROM AUTHOR]

The electrical properties of the solid state/fluid (Ringer solution) interface for phosphorous- and boron-doped porous silicon are reported and the benefits of using porous silicon as neural recording electrodes are discussed. The impedance, reactance and resistance for doped porous and planar silicon, in Ringer solution, were compared to gold electrodes. Planar silicon displayed approximately a three times higher reactance than porous electrodes. The phosphorous-doped porous electrodes displayed a similar reactance compared to the gold electrodes. [ABSTRACT FROM AUTHOR]