m8ta
You are not authenticated, login.
text: sort by
tags: modified
type: chronology
{1360}
hide / / print
ref: -0 tags: L1 cell adhesion neural implants microglia DRG spinal cord dorsal root inflammation date: 11-19-2016 22:55 gmt revision:1 [0] [head]

PMID-22750248 In vivo effects of L1 coating on inflammation and neuronal health at the electrode-tissue interface in rat spinal cord and dorsal root ganglion.

  • Kolarcik CL1, Bourbeau D, Azemi E, Rost E, Zhang L, Lagenaur CF, Weber DJ, Cui XT.
  • Quote: With L1, neurofilament staining was significantly increased while neuronal cell death decreased.
  • These results indicate that L1-modified electrodes may result in an improved chronic neural interface and will be evaluated in recording and stimulation studies.
  • Ok, so this CAM seems to mitigate against microglia / inflammation, but how was it selected vs any of the other CAMs and surface proteins? (This domain is almost completely unknown by me..)
  • Ultimate strategy likely to be a broad combination of mechanical (size, flexibility), biochemical (inflammation, cell migration), electrochamical (surface coatings) and vasculature-avoiding approaches.

{781}
hide / / print
ref: Polikov-2005.1 tags: neural response glia histology immune electrodes recording 2005 Tresco Michigan microglia date: 01-29-2013 00:34 gmt revision:10 [9] [8] [7] [6] [5] [4] [head]

PMID-16198003[0] Response of brain tissue to chronically implanted neural electrodes

  • Good review (the kind where figures are taken from other papers). Nothing terribly new (upon a very cursory inspection)
  • When CNS damage severs blood vessels, microglia are indistinguishable from the blood borne, monocyte-derived macrophages that are recruited by the degranulation of platelets and the cellular release of cytokines.
  • Furthermore, microglia are known to secrete, either constitutively, or in response to pathological stimuli, neurotrophic factors that aid in neuronal survival and growth.
    • Also release cytotoxic and neurotoxic factors that can lead to neuronal death in vitro.
    • It has been suggested that the presence of insoluble materials in the brain may lead to a state of 'frustrated phagocytosis' or inability of the macrophages to remove the foreign body, resulting in persistent release of neurotoxic substances.
  • When a 10x10 array of silicon probes was implanted in feline cortex, 60% of the needle tracks showed evidence of hemorrhage and 25% showed edema upon explantation of the probes after one day (Schmidt et al 1993) {1163}
    • Although a large number of the tracks were affected, only 3-5% of the area was actually covered by hemorrhages and edema, suggesting the actual damage to blood vessels may have been relatively minor. (!!)
  • Excess fluid and cellular debris diminishes 6-8 days due to the action of activated microglia and re-absorption.
  • As testament to the transitory nature of this mechanically induced wound healing response, electrode tracks could not be found in animals after several months when the electrode was inerted and quickly removed (Yuen and Agnew 1995, Rousche et al 2001; Csicsvari et al 2003, Biran et al 2005).
  • Biran et al 2005: observed persistent ED-1 immunoreactivity around silicon microelectrode arrays implanted in rat cortex at 2 and 4 weeks following implantation; not seen in microelectrode stab wound controls.
  • On the glial scar:
    • observed in the CNS of all vertebrates, presumably to isolate damaged parts of the nervous system and maintain the integrity of the blood-brain barrier.
    • mostly composed of reactive astrocytes.
    • presumably the glial scar insulates electrodes from nearby neurons, hindering diffusion and increasing impedance.
  • On the meninges:
    • Meningeal fibroblasts, which also stain for vimentin, but not for GFAP, may migrate down the electrode shaft from the brain surface and form the early basis for the glial scar.
  • On recording quality:
    • Histological examination upon explantation revealed that every electrode with stable unit recordings had at least one large neuron near the electrode tip, while every electrode that was not able to record resolvable action potentials was explanted from a site with no large neurons nearby.
  • Perhaps the clearest example of this variability was observed in the in vivo response to plastic “mock electrodes” implanted in rabbit brain by Stensaas and Stensaas (1976) {1210} and explanted over the course of 2 years. They separated the response into three types: Type 1 was characterized by little to no gliosis with neurons adjacent to the implant, Type 2 had a reactive astrocyte zone, and Type 3 exhibited a layer of connective tissue between the reactive astrocyte layer and the implant, with neurons pushed more than 100 um away. All three responses are well documented in the literature; however this study found that the model electrodes produced all three types of reactions simultaneously,depending on where along the electrode one looked.

____References____

[0] Polikov VS, Tresco PA, Reichert WM, Response of brain tissue to chronically implanted neural electrodes.J Neurosci Methods 148:1, 1-18 (2005 Oct 15)

{748}
hide / / print
ref: Leung-2008.08 tags: biocompatibility alginate tissue response immunochemistry microglia insulation spin coating Tresco recording histology MEA date: 01-28-2013 21:19 gmt revision:4 [3] [2] [1] [0] [head]

PMID-18485471[0] Characterization of microglial attachment and cytokine release on biomaterials of differing surface chemistry

  • The important result is that materials with low protein-binding (e.g. alginate) have fewer bound microglia, hence better biocompatibility. It also seems to help if the material is highly hydrophilic.
    • Yes alginate is made from algae.
  • Used Michigan probes for implantation.
  • ED1 = pan-macrophage marker.
    • (quote:) Quantification of cells on the surface indicated that the number of adherent microglia appeared higher on the smooth side of the electrode compared to the grooved, recording site side (Fig. 2B), and declined with time. However, at no point were electrodes completely free of attached and activated microglial cells nor did these cells disappear from the interfacial zone along the electrode tract.
    • but these were not coated with anything new .. ???

____References____

[0] Leung BK, Biran R, Underwood CJ, Tresco PA, Characterization of microglial attachment and cytokine release on biomaterials of differing surface chemistry.Biomaterials 29:23, 3289-97 (2008 Aug)

{1190}
hide / / print
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)