Design and microfabrication of a polymer-modified carbon sensor array for the measurement of neurotransmitter signals

A novel carbon sensor array has been microfabricated for the spatially distributed measurement of biological Nitric Oxide (NO). NO is intrinsically involved in a large number of brain injury states, like stroke, besides performing a bioregulatory role. The distributed measurement of biological NO signals is expected to be a very useful tool for researchers studying such phenomena. The array consists of microelectrode sites ordered as a 4×4 grid, and has been fabricated on a Si wafer using the photolithography of graphitic carbon. To provide selectivity to NO, in the presence of a large number of possible interfering ionic species, novel polymer coatings were used to modify the properties of the electrode array surface. First, a layer of the anion-blocking resin Nafion was spin-coated. The thickness-spin speed profile for Nafion was determined. The second layer consists of a combination of m-phenylenediamine and resorcinol which functions as a size filter. The resultant electrode array was selective and sensitive to NO at physiological levels, and was not responsive to analogous concentrations of dopamine, ascorbic acid and nitrite. Further, the sensors demonstrated very quick and short response times, making them suitable to measure fast, transient NO signals in the brain or vasculature.