Direct electrochemistry and electrocatalysis of hemoglobin incorporated in composite film based on diblock weak polyelectrolyte PHAEMA-b-PDMAEMA and multi-walled carbon nanotubes

The new composite films composed of diblock weak polyelectrolyte poly(2-hydroxyethyl methacrylate)-b-poly(2-(dimethylamino)ethyl methacrylate) (PHEMA-b-PDMAEMA, noted as PHD in the later content) and multi-walled carbon nanotubes (MWCNTs) were applied to immobilize hemoglobin (Hb) for biosensor fabrication. The characterization of Hb/PHD/MWCNTs films were demonstrated by ultraviolet–visible (UV–vis) spectra, scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and typical amperometric response (i–t) measurements. The immobilized Hb maintains its bioactivities and displays an excellent electrochemical behavior. The modified electrode exhibited good electrocatalytic activity to the reduction of hydrogen peroxide (H2O2). The linear response range of the H2O2 biosensor was from 1.0 × 10−6 to 1.5 × 10−3 M with a detection limit of 3.5 × 10−7 M. The apparent Michaelis–Menten constant of Hb on the PHD/MWCNTs film was estimated to be 0.51 mM. These results indicated that the composite films have potential applicability of new types third-generation biosensors or bioreactors based on direct electrochemistry of the proteins.