Direct electrochemistry and electrocatalysis of hemoglobin immobilized in an amphiphilic diblock copolymer film

A well-defined amphiphilic diblock copolymer, poly [N-(2-methacryloyloxyethyl) pyrrolidone]-block-poly [glycidyl methacrylate] (PNMP-b-PGMA), was applied to immobilize hemoglobin (Hb) in a simple procedure. The characterization of PNMP-b-PGMA/Hb film was demonstrated by ultraviolet–visible (UV–vis) spectra, atomic force microscopy (AFM), and electrochemical impedance spectroscopy (EIS). The electrochemical behaviors of Hb in PNMP-b-PGMA film have been investigated and a pair of well-defined and nearly reversible cyclic voltammetric peaks for the protein heme Fe(III)/Fe(II) redox couples were observed at about −0.409 V (vs. SCE) in pH 7.0 phosphate buffer solution (PBS). The results showed that the PNMP-b-PGMA film improved the protein loading with the retention of bioactivity and greatly promoted the direct electron transfer between Hb and electrode surface. This PNMP-b-PGMA/Hb film modified electrode also exhibited high electrocatalytic effects towards reduction of nitric oxide (NO). These results indicated the potential applicability of the films as new types of third-generation biosensors or bioreactors based on direct electrochemistry of the proteins.