Study on the enhancement of catalytic activity for hemoglobin by quinhydrone in poly(o-aminophenol) film

Hemoglobin (Hb) and quinhydrone (QHQ) were incorporated in poly(o-aminophenol) [o-AP, POAP] film by electropolymerization of o-aminophenol in a weak acid solution containing Hb and QHQ. The nonconducting polymer film was found to be nearly rigid by piezoelectric quartz crystal (PQC) impedance. Therefore, the thickness of the Hb–QHQ–POAP film was estimated as about 104±10 nm by quartz crystal microbalance (QCM). The QHQ mediation effects on the biomacromolecule Hb entrapped in the POAP film were investigated by using cyclic voltammetry, amperometric technique and kinetic study. Cyclic voltammograms showed that the redox peaks in the Hb–QHQ–POAP film are much more reversible than those in the Hb–POAP film. The response current of the Hb–QHQ–POAP film to H2O2 was almost twice than that of the Hb–POAP film. The Michaelis–Menten constant and the activation energy of Hb in the Hb–QHQ–POAP film are 7.47 mM and 13.91 kJ/mol, respectively, both are smaller than that in the Hb–POAP film. These results showed that the immobilized Hb in POAP film exhibited higher catalytic activity to H2O2 due to the mediation of QHQ.