Hemoglobin entrapped within a layered spongy Co3O4 based nanocomposite featuring direct electron transfer and peroxidase activity

Abstract

Layered Co₃O₄ nanoflakes with spongy nanostructure were synthesized for the first time. The porous, layered spongy nanostructure of Co₃O₄ is advantageous for the immobilization of proteins and enzymes, which were integrated with conductive polymer Nafion to form a biocompatible Nafion–Co₃O₄ organic–inorganic hybrid material. Hemoglobin (Hb) was chosen as a model protein to investigate the nanocomposite. FTIR spectroscopy revealed that Hb entrapped in the composite film could retain its essential secondary structure. With advantages of organic–inorganic hybrid materials, dramatically facilitated direct electron transfer of Hb and excellent bioelectrocatalytic activity towards H₂O₂ were demonstrated. The small apparent Michaelis–Menten constant (0.136 mM) and the high sensitivity (396 mA cm⁻² M⁻¹) of the film electrode indicated that Hb in the composite film possessed high enzyme-like peroxidase activity. The Co₃O₄-based hybrid material could be used efficiently for the entrapment of redox-active proteins and may find wide potential applications in biosensors, biocatalysis, bioelectronics and biomedical devices.