Enhanced selectivity and stability of ruthenium purple-modified carbon fiber microelectrodes for detection of hydrogen peroxide in brain tissue

Microelectrodes coupled to fast electrochemical techniques are an attractive approach towards real time in vivo monitoring with minimal damage to living tissue. Here, carbon fiber microelectrodes(CFM) were modified by electrodeposition of ruthenium purple (RP) for monitoring of H2O2 concentration dynamics in brain tissue preparations. The RP-modified CFM (CFM-RP) showed catalytic activity for the reduction of H2O2 at -0.1 V vs. Ag/AgCl in aqueous electrolyte at neutral pH and in the presence of physiological concentration of sodium cation (154 mM). The CFM-RP displayed a linear response in the concentration range of 2-500 mu M, with a sensitivity of 0.98 +/- 0.37 mu A cm(-2) mu M-1 and a limit of detection of 70 +/- 40 nM. Coating the CFM-RP with a Nafion (R) layer greatly extended the operational stability of the RP film to 3 h in a medium containing a high sodium concentration at physiological pH 7.4. Validation of the CFM-RP-Nafion (R) sensor suitability for monitoring H2O2 concentration dynamics was achieved by measuring exogenously and locally applied H2O2 in rodent striatal slices. Together, these results support the excellent analytical performance of this new CFM-RP-Nafion (R) sensor design for sensitive and selective monitoring of H2O2 concentration dynamics in brain tissue.