title: In vitro extracellular recording and stimulation performance of nanoporous gold-modified multi-electrode arrays.
abstract: OBJECTIVE
  Nanoporous gold (Au) structures can reduce the impedance and enhance the charge injection capability of multi-electrode arrays (MEAs) used for interfacing neuronal networks. Even though there are various nanoporous Au preparation techniques, fabrication of MEA based on low-cost electro-codeposition of Ag:Au has not been performed. In this work, we have modified a Au MEA via the electro-codeposition of Ag:Au alloy, followed by the chemical etching of Ag, and report on the in vitro extracellular recording and stimulation performance of the nanoporous Au-modified MEA.
  
  
  METHODS
  Ag:Au alloy was electro-codeposited on a bilayer lift-off resist sputter-deposition passivated Au MEA followed by chemical etching of Ag to form a porous Au structure.
  
  
  RESULTS
  The porous Au structure was analyzed by scanning electron microscopy and tunneling electron microscopy and found to have an interconnected nanoporous Au structure. The impedance value of the nanoporous Au-modified MEA is 15.4 ± 0.55 kΩ at 1 kHz, accompanied by the base noise V rms of 2.4 ± 0.3 μV. The charge injection limit of the nanoporous Au-modified electrode estimated from voltage transient measurement is approximately 1 mC cm(-2), which is comparable to roughened platinum and carbon nanotube electrodes. The charge injection capability of the nanoporous Au-modified MEA was confirmed by observing stimulus-induced spikes at above 0.2 V. The nanoporous Au-modified MEA showed mechanical durability upon ultrasonic treatment for up to an hour.
  
  
  CONCLUSIONS
  Electro-codeposition of Ag:Au alloy combined with chemical etching Ag is a low-cost process for fabricating nanoporous Au-modified MEA suitable for establishing the stimulus-response relationship of cultured neuronal networks.
authors.affiliation: Synapse Devices Creative Research Center, Electronics and Telecommunications Research Institute, 218 Gajeong-ro, Yuseong-gu, Daejeon 305-700, Korea.
authors.forename: Yong Hee
authors.initials: YH
authors.lastname: Kim
authors.forename: Gook Hwa
authors.initials: GH
authors.lastname: Kim
authors.forename: Ah Young
authors.initials: AY
authors.lastname: Kim
authors.forename: Young Hwan
authors.initials: YH
authors.lastname: Han
authors.forename: Myung-Ae
authors.initials: MA
authors.lastname: Chung
authors.forename: Sang-Don
authors.initials: SD
authors.lastname: Jung
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D004558:Electric Stimulation / Q000379:methods; D045604:Extracellular Fluid / Q000502:physiology*; D006046:Gold / Q000737:chemistry*; D053768:Metal Nanoparticles / Q000737:chemistry*; D008839:Microelectrodes; D009474:Neurons / Q000502:physiology*; D016062:Porosity; D051381:Rats; D017207:Rats, Sprague-Dawley
chemical_list: D006046:Gold