Direct electrochemistry of hemoglobin and myoglobin at didodecyldimethylammonium bromide-modified powder microelectrode and application for electrochemical detection of nitric oxide

Hemoglobin (Hb) and myoglobin (Mb) were immobilized at the didodecyldimethylammonium bromide (DDAB)-modified powder microelectrode (PME) to fabricate Hb–DDAB–PME and Mb–DDAB–PME. Direct electrochemistry of Hb and Mb were achieved on the DDAB-modified PME. The formal potential was −0.224 V for Hb and −0.212 V for Mb (vs. SCE). The apparent surface concentration of Hb and Mb at the electrode surface was 2.83 × 10−8 and 9.94 × 10−8 mol cm−2. The Hb–DDAB–PME and Mb–DDAB–PME were successfully applied for measurement of NO in vitro. The anodic current peaks for NO oxidation at +0.7 V and the cathodic current peaks for NO reduction at −0.85 V on the CV curves were obtained on the modified electrodes. For detection of NO at +0.7 V, the sensitivity is 3.31 mA μM−1 cm−2 for Hb–DDAB–PME and 0.6 mA μM−1 cm−2 for Mb–DDAB–PME. The detection limit is 5 nM for Hb–DDAB–PME and 9 nM for Mb–DDAB–PME. The linear response range is 9–100 and 28–330 nM for Hb- and Mb-modified PME, respectively. For the electrochemical detection of NO at −0.85 V by using Hb–DDAB–PME, the detection sensitivity is 39.56 μA μM−1 cm−2; the detection limit is as low as 0.2 μM; and the linear response range is 1.90–28.08 μM.