Electroactive hemoglobin–surfactant–polymer biomembrane-like films

Polyions complex 2C₁₂N⁺PSS⁻ was prepared by reacting poly(sodium styrenesulfonate) (Na⁺PSS⁻) with didodecyldimethylammonium bromide (2C₁₂N⁺Br⁻). Stable thin films made from 2C₁₂N⁺PSS⁻ with incorporated redox protein hemoglobin (Hb) on pyrolytic graphite (PG) electrodes were then characterized by electrochemistry and other techniques. Cyclic voltammetry (CV) of Hb–2C₁₂N⁺PSS⁻ films showed a pair of well-defined and nearly reversible peaks for HbFe(III)/Fe(II) couple at about −0.17 V vs. saturated calomel electrode (SCE) in pH 5.5 buffers. The electron transfer rate between Hb and PG electrode was greatly facilitated in microenvironment of 2C₁₂N⁺PSS⁻ films. Positions of Soret absorption band suggest that Hb keeps its secondary structure similar to its native state in 2C₁₂N⁺PSS⁻ films at the medium pH. The results of X-ray diffraction and differential scanning calorimetry (DSC) suggest synthesized lipid 2C₁₂N⁺PSS⁻ films have an ordered bilayer structure intercalated between PSS⁻ polyion layers, and the incorporated Hb expands the layer spacing of the films. HbFe(I), a highly reduced form of Hb, might also be produced in these films at about −1.09 V, and could be used to catalytically reduce organohalide pollutants.