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Nanoengineering of neuronal growth substrates

Nanoengineering of neuronal growth substrates. Complex architecture of vertical and lateral micropatterns Polylysine, gelatin, Phospholipase A, or BSA. Template used for LBL-LO fabrication process. (a), (b)photolithography, (c) LbL assembly process, (d) LbL processed chips,

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Nanoengineering of neuronal growth substrates

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  1. Nanoengineering of neuronal growth substrates • Complex architecture of vertical and lateral micropatterns • Polylysine, gelatin, Phospholipase A, or BSA

  2. 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.

  3. Confocal scanning shows separate dye regions: selective patterning of peptides Biomacromolecules: 5: 1745, 2004.

  4. Green squares have PLA (top 2) . Red squares (bottom) have BSA.

  5. 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-Ln]8 He, W. Biomaterials 26: 2983, 2005

  6. 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 > 100 kHz (in vitro), but Cell membrane impedance filters @ 1Khz. I.e. time constant of V response….

  7. Pushing on OHC with piezo Kennedy et al. Nature, 2005

  8. Mech Propertis of OHC • Negative stiffness = force generation

  9. Force generation by OHC Kennedy et al. Nature, 2005

  10. Role of Ca++

  11. 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.

  12. 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

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

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