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{1371}
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ref: -0 tags: nanotube tracking extracellular space fluorescent date: 02-02-2017 22:13 gmt revision:0 [head]

PMID-27870840 Single-nanotube tracking reveals the nanoscale organization of the extracellular space in the live brain

  • Extracellular space (ECS) takes up nearly a quarter the volume of the brain (!!!)
  • Used the intrinsic fluorescence of single-walled carbon nanotubes @ 1um, 845nm excitation, with super-resolution tracking of diffusion.
    • Were coated in phospholipid-polyethylene glycol (PL-PEG), which display low cytotoxicity compared to other encapsulants.
  • 5ul, 3ug/ml injected into the ventricles of young rats; allowed to diffuse for 30 minutes post-injection.
  • No apparent response of the microglia.
  • Diffusion tracking revealed substantial dead-space domains in the ECS.
    • As compared to patch-clamp loaded SWCNTs
  • Estimate from parallel and perpendicular diffusion rates that the characteristic scale of ECS dimension is 80 to 270nm, or 150 +- 40nm.
  • The ECS nanoscale dimensions as visualized by tracking similar in dimension and tortuosity to electron microscopy.
  • Viscosity of the extracellular matrix from 1 to 50 mPa S, up to two orders of magnitude higher than the CSF.
  • Positive control through hyalurinase + several hours to digest the hyaluronic acid.
    • But no observed changes in morphology of the neurons via confocal .. interesting.
    • Enzyme digestion normalized the spatial heterogenaity of diffusion.

{1327}
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ref: -0 tags: ice charles lieber silicon nanowire probes su-8 microwire extracellular date: 10-14-2016 23:28 gmt revision:2 [1] [0] [head]

PMID-26436341 Three-dimensional macroporous nanoelectronic networks as minimally invasive brain probes.

  • Xie C1, Liu J1, Fu TM1, Dai X1, Zhou W1, Lieber CM1,2.
  • Again, use silicon nanowire transistors as sensing elements. These seem rather good; can increase the signal, and do not suffer from shunt resistance / capacitance like wires.
    • They're getting a lot of mileage out of the technology; initial pub back in 2006.
  • Su-8, Cr/Pd/Cr (stress elements) and Cr/Au/Cr (conductor) spontaneously rolled into a ball, then the froze in LN2. Devices seemed robust to freezing in LN2.
  • 300-500nm Su-8 passivation layers, as with the syringe injectable electrodes.
  • 3um trace / 7um insulation (better than us!)
  • Used 100nm Ni release layer; thin / stiff enough Su-8 with rigid Si support chip permitted wirebonding a connector (!!)
    • Might want to use this as well for our electrodes -- of course, then we'd have to use the dicing saw, and free-etch away a Ni (or Al?) polyimide adhesion layer -- or use Su-8 like them. See figure S-4
  • See also {1352}

{1045}
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ref: Vibert-1979.08 tags: spike sorting recording depth extracellular glass electrodes active feedback original date: 01-15-2012 06:46 gmt revision:3 [2] [1] [0] [head]

PMID-95711[0] Spike separation in multiunit records: A multivariate analysis of spike descriptive parameters

  • Glass coated tungsten microeletrodes have high capacitance; they compensate for this by spraying colloidal silver over the outside sheath of the glass, insulating that with varnish, and driving the shield in a positive-feedback way (stabillized in some way?) This negates the capacitance. 'low impedance capacitance compensated'.
    • Capacitance compensation really matters!!
  • Were able to record from single units for 40-100um range (average: 50um) with SNRs 2:1 to 7:1.
    • Some units had SNRs that could reach 15:1 (!!!), these could be recorded for 600 um of descent.
    • more than 3 units could usually be recognized at each recording point by visual inspection of the oscilloscope, and in some cases up to 6 units could be distinguished
    • Is there some clever RF way of neutralizing the capacitance of everything but the electrode tip? Hmm. Might as well try to minimize it.
  • Bandpass 300 Hz - 10 kHz.
  • When the signal crossed the threshold level, it was retained and assumed to be a spike if the duration of the first component was between 70 and 1000 us.
    • This 70 us lower limit was determined on a preliminary study as a fairly good rise time threshold for separation of fiber spikes from somatic or dendritic spikes.
    • I really need to do some single electrode recordings. Platt?
  • Would it be possible to implement this algorithm in realtime on the DSP?
  • Describe clustering based on PCA.
  • Programming this computer (PDP-12) must have been crazy!
  • They analyzed 20k spikes. Mango gives billions.
  • First principal component (F1) represented 60-65% of total information was based mostly on amplitude
  • Second principal component, 15-20% of total information represented mainly time parameters.
  • Suggested 3 parameters: Vmax, Vmin, and T3 (time from max to min).
  • Maybe they don't know what they are talking about:

____References____

[0] Vibert JF, Costa J, Spike separation in multiunit records: a multivariate analysis of spike descriptive parameters.Electroencephalogr Clin Neurophysiol 47:2, 172-82 (1979 Aug)

{841}
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ref: Tian-2010.08 tags: nanowire nanoprobe silicon FET doping cis trans extracellular intracellular recording neuro MEA date: 01-03-2012 16:35 gmt revision:4 [3] [2] [1] [0] [head]

PMID-20705858[0] Three-Dimensional, Flexible Nanoscale Field-Effect Transistors as Localized Bioprobes

  • Made a silicon nanowire with 60 deg. kinks via trans/cis manipulation.
  • Doped one part of the N nanowire P to make a 200nm long FET whose gate is simply the surface of the nanowire (I think, have to check the refs)
  • Attached the nanoprobe / nanowire to flexible PMMA / SM-8 support which, due to interfacial stress, rose off the substrate (clever!)
  • Coated tip with phospholipid layers -> better cell attachment / penetration.
    • Possible to have the cell pull the nanoprobe in via endocytic pathways.
  • Were able to record intracellular and extracellular AP from rabbit cardiocytes. (!!!)

____References____

[0] Tian B, Cohen-Karni T, Qing Q, Duan X, Xie P, Lieber CM, Three-dimensional, flexible nanoscale field-effect transistors as localized bioprobes.Science 329:5993, 830-4 (2010 Aug 13)