Adenosine (ADO) and 2,8-dihydroxyadenine (2,8-DHA) were prepared before PCI34051 experiments in 31 mM phosphate buffer (pH 7.4). Potassium ferricyanide was prepared in 0.5 M KCl (pH 6.0). All determinations were performed at room temperature. The percentage of CO2 in air of 0.03% and of oxygen of 21% was not changed and the solutions were not purged with gases. The sensitivity of each analyte was determined from the slopes of the calibration curves. At least 8 points for each calibration curve and 4 determinations at each concentration were obtained at three different electrodes. The results obtained at different CFEs were pooled. All other measurements were repeated at least in triplicate. The reported results reflect the reproducibility of the measurements and the reproducibility of fabrication of carbon fiber sensors.
The instrumental set up has been described previously (Kathiwala et al., 2010). Bioanalytical Systems Electrochemical Analyzer (BAS-100, West Lafayette, IN) with a cytosine home-built preamplifier was interfaced to a PC and was used in slow scan cyclic voltammetry. A two-electrode configuration was used, with CFE as working and SCE as reference. In slow scan voltammetry, the potential scan rate was (50 mV s−1); the potential window was −0.2 to 0.5 V for ferricyanide.