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ref: Biran-2005.09 tags: microelectrode Michigan probe glia tissue response electrode immune histology MEA Biran date: 01-24-2013 20:49 gmt revision:5 [4] [3] [2] [1] [0] [head]

PMID-16045910[0] Neuronal cell loss accompanies the brain tissue response to chronically implanted silicon microelectrode arrays.

  • See also {1190} (wow, I'm redundant!)
  • Important point: ED1 up-regulation and neuronal loss were not observed in microelectrode stab controls, indicating that the phenotype did not result from the initial mechanical trauma of electrode implantation, but was associated with the foreign body response.
    • CD68 = ED1 is a marker for microglia and other macrophages. (wikipedia article is informative).
    • GFAP = glial fibrillary acidic protein, marker for astrocytes.
  • Recording failure is caused by chronic inflammation (mostly activated microglia) at the microelectrode brain tissue interface.
  • Only tested response 2 and 4 weeks after implantation. Makes sense for stab wound, but didn't the want to see a longer term response? Or do their electrodes just not last that long?
  • What did they coat the silicon probes in?
  • Used silastic to shock-mount their floating electrodes, but this apparently made no difference compared to conventional dental cement and bone screw mounting.
  • Suggest that chronic inflammatory response may be related to the absorption of fibrogen and complement to the surface of the device (device should not be porous?), the subsequent release of pro-inflammatory and cytotoxic cytokines by activated microphages, and the persistence of activated macrophages around materials which cannot be broken down.
    • Well then, how do you make the electrodes biochemically / biologically 'invisible'?
    • Persistently activated microglia are found around insoluble plaques in AD (plaques that cannot be / are not removed from the brain via proteolysis. Microglia form 'glitter cells' when they engulf undigestible stubstances). This has been termed 'frustrated phagocytosis', which results in increased secretion of proinflamatory cytokines that directly or indirectly cause neuronal death.
  • Significant reductions in neurofiliament reactivity was seen up to 230um from the microelectrode interface; this was not seen for stab wounds. Maximum recording distance is about 130um; 100um more reasonable in normal conditions.
  • Accumulating evidence from postmortem analysis of patients implanted with DBS electrodes reveals that chronic neuroinflamation is part of the response to such (duller, larger) implants as well. They have seen cell loss up to 1mm fromt the electrode surface here.

____References____

[0] Biran R, Martin DC, Tresco PA, Neuronal cell loss accompanies the brain tissue response to chronically implanted silicon microelectrode arrays.Exp Neurol 195:1, 115-26 (2005 Sep)

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ref: Biran-2007.07 tags: tresco biocompatibility tether skull electrodes Michigan probe recording Tresco date: 01-24-2013 20:11 gmt revision:6 [5] [4] [3] [2] [1] [0] [head]

PMID-17266019[0] The brain tissue response to implanted silicon microelectrode arrays is increased when the device is tethered to the skull.

  • Good, convincing, figures.

____References____

[0] Biran R, Martin DC, Tresco PA, The brain tissue response to implanted silicon microelectrode arrays is increased when the device is tethered to the skull.J Biomed Mater Res A 82:1, 169-78 (2007 Jul)

{1190}
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ref: Biran-2005.09 tags: Tresco histology chronic implantation astrocytes microglia date: 01-04-2013 02:28 gmt revision:3 [2] [1] [0] [head]

PMID-16045910[0] Neuronal cell loss accompanies the brain tissue response to chronically implanted silicon microelectrode arrays.

  • We observed persistent ED1 immunoreactivity around implanted silicon microelectrode arrays implanted in adult rat cortex that was accompanied by a significant reduction in nerve fiber density and nerve cell bodies in the tissue immediately surrounding the implanted silicon microelectrode arrays.
  • We found that explanted electrodes were covered with ED1/MAC-1 immunoreactive cells and that the cells released MCP-1 and TNF-a under serum-free conditions in vitro.
  • See also [1] and [2]
  • Electrodes: Michigan type, 5mm long, 200um wide tapering to 30um, 15um thick at the shank tapering to 2um.
    • Show that the chronic response is markedly different than acute stab wounds.
    • "Stab wounds resulted in comparatively minimal neurofilament loss at 2 weeks (A) and no apparent loss by 4 weeks".
    • "The number of neuronal bodies is reduced in the area adjacent to microelectrodes (B, D) but appears unaltered surrounding stab wound lesions (A, C; lesion site in center of each image)."
  • Includes details of immunostaining, which could be useful.

____References____

[0] Biran R, Martin DC, Tresco PA, Neuronal cell loss accompanies the brain tissue response to chronically implanted silicon microelectrode arrays.Exp Neurol 195:1, 115-26 (2005 Sep)
[1] Szarowski DH, Andersen MD, Retterer S, Spence AJ, Isaacson M, Craighead HG, Turner JN, Shain W, Brain responses to micro-machined silicon devices.Brain Res 983:1-2, 23-35 (2003 Sep 5)
[2] Gilletti A, Muthuswamy J, Brain micromotion around implants in the rodent somatosensory cortex.J Neural Eng 3:3, 189-95 (2006 Sep)