Biocompatibility of silicon-based electrode arrays implanted in feline cortical tissue.
The passive biocompatibility of silicon-based electrode arrays was studied in feline cortical tissue. Three types of arrays were used: uncoated, coated with polyimide, and coated with polyimide over an adhesion promoter. Fifteen arrays were implanted for 24 h to determine early tissue reaction to the implantation procedure, and twelve arrays were implanted for 6 months to determine structural and material biocompatibility. Edema and hemorrhage were present around the short-term implants, but involved less than 6% of the total area of the tissue covered by the array. With chronic implants, leukocytes were rarely present and macrophages were found around roughly one-third of the tracks. Remnants of foreign material from the electrodes could be identified in less than 10% of the tracks. Gliosis was found around all tracks, forming an annulus between 20 and 40 microns thick. A capsule was not always present, and never exceeded a thickness of 9 microns. These results suggest that the implantation procedure produces limited amounts of tissue damage, and that the arrays are biocompatible. However, the arrays insulated with polyimide over a primer had significantly greater involvement of macrophages, gliosis, and capsule formation than uncoated arrays and arrays insulated with polyimide without printer, perhaps indicating a reaction to aluminum oxide in the primer.
Schmidt
S
S
Department of Bioengineering, University of Utah, Salt Lake City 84112.
Horch
K
K
Normann
R
R
D000818:Animals; D002415:Cats; D002540:Cerebral Cortex; D004487:Edema / Q000209:etiology; D004567:Electrodes, Implanted; D006470:Hemorrhage / Q000209:etiology; D008213:Lymphocyte Activation; D008422:Materials Testing; D019736:Prostheses and Implants; D012825:Silicon
D012825:Silicon