Analysis of carbon nanofibers and porous silicon for neural applications

Chronic neural implants are usually made from silicon materials and are subject to scar tissue formation at the tissue/implant interface, which interferes with their functionality. Carbon nanofibers are an example of a material that may improve neural implant interactions with native cell populations since these nanofibers have promising cytocompatibility, mechanical, and electrical properties. Neural implants may achieve better tissue interactions simply by incorporating carbon nanofibers into a silicon matrix. The objective of the present in vitro study was to determine cytocompatibility properties of carbon nanofibers and porous silicon materials. Carbon fiber substrates were prepared from carbon fibers with either nanoscale or micron scale diameters, and both high and low surface energy fibers were investigated. Porous silicon was prepared by treatments resulting in mesoscale pores with nanoscale roughness between pores. Astrocytes (glial scar tissue-forming cells) were seeded separately onto the carbon fiber and silicon substrates. Astrocytes preferentially adhered on the largest diameter carbon fiber with the lower surface energy and preferred the silicon sample with the greatest porosity. These results indicate that nanoscale surface roughness may deter astrocyte adhesion. Controlling carbon fiber diameter and silicon porosity may be approaches for increasing implant contact with neurons and decreasing scar tissue formation.