Histopathological evaluation of materials implanted in the cerebral cortex.
Histopathological changes of the cerebral cortex in response to small, penetrating metal and non-metal implants were analyzed by means of light and electron microscopy. The needle-shaped implants were left in place during all stages of histological preparation and embedded in plastic together with the cortex. Changes of the brain-implant boundary were classified as non-reactive, reactive, or toxic, according to the reactive cellular constituents. Among the non-reactive materials were several plastics and metals such as aluminum, gold, platinum, and tungsten. The boundary of these implants displayed little or no gliosis and normal neuropile with synapses within 5 micron of the implant's surface. The boundary of reactive materials such as tantalum or silicon dioxide was marked by multinucleate giant cells and a thin layer (10 micron)) of connective tissue. Toxic materials such as iron and copper were separated from the cortical neuropile by a capsule of cellular connective tissue and a zone of astrocytosis. Cobalt, a highly toxic material, produced more extensive changes in the zones of connective tissue and astrocytes. These results indicate that a variety of materials are well tolerated by the brain and could be used in the fabrication of neuroprosthetic devices.
D000535:Aluminum; D000818:Animals; D001672:Biocompatible Materials; D002540:Cerebral Cortex / Q000473:pathology*; D003035:Cobalt; D003238:Connective Tissue; D003300:Copper; D005911:Gliosis; D006046:Gold; D007501:Iron; D010969:Plastics; D010984:Platinum; D011817:Rabbits; D012825:Silicon; D013569:Synapses; D013635:Tantalum; D014414:Tungsten
D001672:Biocompatible Materials; D010969:Plastics; D003035:Cobalt; D010984:Platinum; D013635:Tantalum; D006046:Gold; D003300:Copper; D000535:Aluminum; D007501:Iron; D014414:Tungsten; D012825:Silicon