Direct electrochemistry and electrocatalysis of heme-proteins in regenerated silk fibroin film

Abstract

A biocompatible silk fibroin (SF) film provided a feasible microenvironment for heme-proteins to direct electron transfer on graphite electrodes (GE). Myoglobin (Mb), hemoglobin (Hb), horseradish peroxidase (HRP), and catalase (Cat) in corporated in SF films exhibited a pair of well-defined, nearly reversible cyclic voltammetric peaks, corresponding to the reaction of hemeFe (III) + e → hemeFe (II). The formal potential ( E 0), the apparent coverage ( Γ) and the electron transfer rate constant ( k s) of four proteins in SF films were evaluated by analyzing the cyclic voltammograms (CVs) of heme-proteins. The formal potential was pH dependent, suggesting that proton ion was involved in the reaction. Ultraviolet visible (UV–vis) spectra and reflectance absorbance infrared (RAIR) spectra indicated that heme-proteins in SF films were not grossly denatured. The structure of heme-proteins–SF films was investigated using scanning electron microscopy (SEM) and RAIR. It indicated that there existed intermolecular interaction between heme-proteins and SF and this governed their different morphology in SF films. Hydrogen peroxide and nitric oxide were catalytically reduced by the heme-proteins in SF films, showing the potential applicability of the heme-proteins–SF films as the new type of biosensors based on the protein film voltammetry.