Glutaraldehyde cross-linked glutamate oxidase coated microelectrode arrays: selectivity and resting levels of glutamate in the CNS

ACS Chem Neurosci. 2013 May 15;4(5):721-8. doi: 10.1021/cn4000555. Epub 2013 May 9.


Glutaraldehyde is widely used as a cross-linking agent for enzyme immobilization onto microelectrodes. Recent studies and prior reports indicate changes in enzyme activity and selectivity with certain glutaraldehyde cross-linking procedures that may jeopardize the performance of microelectrode recordings and lead to falsely elevated responses in biological systems. In this study, the sensitivity of glutaraldehyde cross-linked glutamate oxidase-based microelectrode arrays to 22 amino acids was tested and compared to glutamate. As expected, responses to electroactive amino acids (Cys, Tyr, Trp) were detected at both nonenzyme-coated and enzyme-coated microelectrodes sites, while the remaining amino acids yielded no detectable responses. Electroactive amino acids were effectively blocked with a m-phenylene diamine (mPD) layer and, subsequently, no responses were detected. Preliminary results on the use of poly(ethylene glycol) diglycidyl ether (PEGDE) as a potentially more reliable cross-linking agent for the immobilization of glutamate oxidase onto ceramic-based microelectrode arrays are reported and show no significant advantages over glutaraldehyde as we observe comparable selectivities and responses. These results support that glutaraldehyde-cross-linked glutamate oxidase retains sufficient enzyme specificity for accurate in vivo brain measures of tonic and phasic glutamate levels when immobilized using specific "wet" coating procedures.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Amino Acid Oxidoreductases / drug effects*
  • Amino Acid Oxidoreductases / physiology
  • Biosensing Techniques
  • Cross-Linking Reagents / pharmacology*
  • Enzymes, Immobilized / drug effects*
  • Enzymes, Immobilized / physiology
  • Glutamic Acid / analysis*
  • Glutaral / pharmacology*
  • Microelectrodes


  • Cross-Linking Reagents
  • Enzymes, Immobilized
  • Glutamic Acid
  • Amino Acid Oxidoreductases
  • L-glutamate oxidase
  • Glutaral