A facile method for the immobilization of myoglobin on multi-walled carbon nanotubes: Poly(methacrylic acid-co-acrylamide) nanocomposite and its application for direct bio-detection of H2O2

Poly(methacrylic acid-co-acrylamide) (P(MAA-co-AAM)), noncovalently attached on the surface of multiwalled carbon nanotubes (MWCNTs) through hydrophobic interactions, hydrogen bonding or electrostatic attraction, was employed for the first time as a novel matrix for enzyme immobilization to develop highly sensitive amperometric biosensors. The effective interaction between P(MAA-co-AAM) and MWCNTs, and the structural morphology of the as-prepared P(MAA-co-AAM)–MWCNTs nanocomposite were characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Further experimental results show that the solubility and stability of as-prepared P(MAA-co-AAM)–MWCNTs nanocomposites in water are better than that of pristine MWCNTs, and no significant electronic and structural change was observed after functionalization. When myoglobin (Mb) was selected as a model protein, studies by Ultraviolet–visible (UV–vis) and Circular dichroism (CD) spectroscopy indicate that the encapsulated Mb in the as-prepared P(MAA-co-AAM)–MWCNTs nanocomposites, was kept in a near-native state, indicating the P(MAA-co-AAM)–MWCNTs nanocomposites have good biocompatibility for protein/enzyme immobilization. The fabricated electrochemical biosensor based on the immobilized Mb reveals fast response of less than 3 s, wide linear range from 1.47 × 10−6 M to 4.76 × 10−3 M and good detection limit as low as 7.60 × 10−7 M toward the electro-determination of hydrogen peroxide (H2O2) under optimal experimental conditions.