Nanoengineering of neuronal growth substrates

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Nanoengineering of neuronal growth substrates

• Complex architecture of vertical and lateral
  micropatterns
• Polylysine, gelatin, Phospholipase A, or BSA

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Template used for LBL-LO fabrication process

• (a), (b)photolithography, (c) LbL assembly
  process, (d) LbL processed chips,
• (e) after lift-off, (f) top view of the
  fabricated chip green-FITC labeled sPLA2,
  red-TRITC labeled BSA/PLL/gelatin.

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Confocal scanning shows separate dye regions
selective patterning of peptides
Biomacromolecules 5 1745, 2004.
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• Green squares have PLA (top 2) . Red squares
  (bottom) have BSA.

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Nanoscale neuro coatings

• LbL layer by layer PEI/Ln- onto Si. Polyion
  glue
• Coatings need isoelectric pt. Away from neutral
  pH.
• QCM to weigh layer, ELISA to assay Ln sites
• Impedance spectroscopy
• Reduce scarring fibro-encapsulation?.
• PEI is linear, CH is bulky

uncoated
PEI-Ln8
He, W. Biomaterials 26 2983, 2005
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Hearing sensitivity?

• 100 hairs in a hair cell (inner) transduce
  bending
• Outer hair cells are silent majority that bend
  actively for amplification of motion
• High Speed of OHCs ?
• Electromotility of OHCs prestin BW gt 100 kHz
  (in vitro), but Cell membrane impedance filters _at_
  1Khz. I.e. time constant of V response.

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Pushing on OHC with piezo
Kennedy et al. Nature, 2005
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Mech Propertis of OHC

• Negative stiffness force generation

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Force generation by OHC
Kennedy et al. Nature, 2005
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Role of Ca
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Boltzman model

• where P's are the probabilities of states or
  classes 1 and 2, and DF is free energy. For
  example Pi can represent the concentration of
  particles in 2 separate compartments. Lets say
  the energy in the first compartment is F1 and in
  the second, it is F2, and DF F2-F1. Since the
  particles must either be in compartment 1 or 2,
  then P1 P2 1.

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• DPOAE level Ldp measured for EMF-exposure, i.e.,
  within transmission pauses rhombuses!, and for
  sham exposure filled circles!, for one
  individual subject. Open circles indicate
• the corresponding noise-floor level Lnoise .
  There were 12 different
• tests where frequency f 2 and level L2 of the
  primary tones were varied. f 2
• and L2 are indicated at the respective panels
  A!L!. Chosen case is representative
• of the 24 subjects in whom the EMF-correlated
  change in DPOAE
• level was smaller than 0.25

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Measuring cochlear function

• Distortion product otoacoustic emissions
• Two tones given to ear 2f1-f2 best DPOAE
• Most sensitive assay of cochlear function