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Anna Belle1 Allison Yorita1 Anna Ivanovskaya1 Jeanine Pebbles1 Vanessa Tolosa1

1, Lawrence Livermore National Laboratory, Livermore, California, United States

To understand and diagnose neurological disorders, it is important not only to detect levels of a single chemical in the brain but to simultaneously examine the changing ratios of chemical and electrical signals in the brain. In pursuit of a device that can achieve this goal, we have developed a flexible MEA that allows for monitoring of long-term local tissue responses in an awake, freely moving animal. While the device itself can now survive for many months in the body, the enzymatic glutamate sensors integrated into these arrays are not yet robust enough to detect in vivo glutamate changes beyond a week. Here we demonstrate improved lifetimes for glutamate sensors thanks a combination of surface modifications that improve the sensitivity and robustness of these sensors. We’ve developed a unique procedure allows us to nondestructively roughen thin film platinum microelectrodes to improve adhesion of coatings like platinum iridium or iridium oxide to the electrode surface and increase sensitivity of chemical sensors 3-fold. This extreme roughening of a thin film without corrosion is possible via the use of a non-adsorbing electrolyte for the electrochemical roughening to prevents preferential grain boundary dissolution seen with adsorbing electrolytes. In addition, lifetime of these sensors has been improved thanks to modifications to enzyme immobilization and attachment to the array. The enzyme is now matrixed with special nanoScyl capsule that protects enzyme from breakdown or dissolution. Thanks to these modifications, our chemical sensors are moving towards a longer functional lifetime in vivo compatible with the longer lifetime of the arrays themselves.

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