Direct electrochemistry of hemoglobin in poly(acrylonitrile-co-acrylic acid) and its catalysis to H2O2

Hemoglobin (Hb) was successfully immobilized in poly(acrylonitrile-co-acrylic acid) (PAN-co-PAA) film modified glassy carbon electrode (GCE). The Hb-PAN-co-PAA film exhibited a pair of well-defined and quasi-reversible cyclic voltammetric peaks for Hb Fe(III)/Fe(II) redox couple in a pH 7.0 phosphate buffer. The formal potential of Hb heme Fe(III)/Fe(II) couple varied linearly with the increase of pH in the range of 4.0–8.0 with a slope of −53.5 mV pH−1, implying that one proton was accompanied with one electron transferred in the electrochemical reaction. Position of Soret absorption band of Hb-PAN-co-PAA film suggested that the Hb kept its secondary structure similar to its native state in the PAN-co-PAA matrix. The protein in PAN-co-PAA matrix acted as a biologic catalyst to catalyze reduction of hydrogen peroxide. The electrocatalytic response showed a linear dependence on the H2O2 concentration ranging from 9.2 × 10−6 to 2 × 10−3 M with a detection limit of 4.5 × 10−6 M at 3σ.