A cytochrome c modified-conducting polymer microelectrode for monitoring in vivo changes in nitric oxide.

A nitric oxide (NO) microbiosensor based on cytochrome c (cyt c), a heme protein, immobilized onto a functionalized-conducting polymer (poly-TTCA) layer has been fabricated for the in vivo measurement of NO release stimulated by an abuse drug cocaine. Based on the direct electron transfer of cyt c, determination of NO with the cyt c-bonded poly-TTCA electrode was studied using cyclic voltammetry and chronoamperometry. Interferences for the sensory of NO by foreign species such as oxygen and hydrogen peroxide were minimized by covering a Nafion film on the modified electrode surface. Cyclic voltammograms taken using the cyt c/poly-TTCA electrode with NO solutions show a reduction peak at -0.7 V. The calibration plot showed the hydrodynamic range of 2.4-55.0 microM. The detection limit was determined to be 13+/-3 nM based on S/N=3. The microbiosensor was applied into the rat brain to test fluctuation of NO evoked by the abuse drug cocaine. The concentrations of NO levels by acute and repeated injections of cocaine were determined to be 1.13+/-0.03 and 2.13+/-0.05 microM, respectively, showing high sensitivity of the microbiosensor in monitoring NO concentrations in the in vivo intact brain.