Stationary-state oxidized platinum microsensor for selective and on-line monitoring of nitric oxide in biological preparations

Despite the multifaceted biomedical significance of NO, little progress has been achieved so far in the quantitative understanding of the signal trans duction mechanisms where NO is involved. To help progress in this area, we propose a simple electrochemical NO sensor here, consisting of a glass seal ed platinum microdisk electrode coated with cellulose acetate to reduce bot h surface fouling by proteins and response to potential interferences. A di fferential amperometry protocol is optimized to improve selectivity and pro vide a stationary oxidation state of the platinum surface, which prevents l oss in sensitivity during long-term use. We found the oxidation of NO by O- 2 second order in [NO] with a rate constant of (8.0 +/- 0.4) x 10(6) M-2 s( -1), in good agreement with literature data obtained by other than electroc hemical methods. The release rates of NO detected in cultures of activated macrophages were on the order of 20 pmol/(10(6) cells s) and correlated wel l with the nitrite content determined by the spectrophotometric Griess assa y.