Direct electron transfer of hemoglobin on DDAB/SWNTs film modified Au electrode and its interaction with Taxol

Direct electrochemistry of hemoglobin (Hb) immobilized on the DDAB/SWNTs film modified Au electrode was investigated. The immobilized Hb displayed a couple of stable and well-defined redox peaks with the formal potential (E0′) is of about 0.129 V (versus SCE) in a pH 7.0 phosphate buffer solution (PBS). The formal potential of the heme Fe(III)/Fe(II) couple shifted linearly with pH with a slope of −46.8 mV/pH, denoting that an electron transfer accompanies single proton transportation. Both single-wall carbon nanotubes (SWNTs) and didodecyldimethylammonium bromide (DDAB) could accelerate the electron transfer between Hb and the electrode. Using the DDAB/Hb/SWNTs film modified Au electrode, the interaction between Hb and Taxol was studied. The linear response range of the Taxol concentration was from 1.4 × 10−5 to 1.0 × 10−4 M, the linear regression equation was I (μA) = 6.774 − 0.4562C (10−5 M) with a correlation coefficient (r) 0.9986, and the detection limit was 2.80 × 10−6 M (S/N = 3).