Immobilization of hemoglobin on MnCO₃ sphere-loaded Au nanoparticles as highly efficient sensing platform towards hydrogen peroxide

In this paper, we report the synthesis of MnCO₃−Au hybrid microspheres and their application on the electrochemical biosensing of hydrogen peroxide (H₂O₂) based on the immobilization of hemoglobin (Hb). The characterization of MnCO₃−Au microspheres revealed that an abundance of Au nanoparticles (AuNPs) has been absorbed on the surface of the spherical MnCO₃ by the electrostatic assembly. The combined unique properties of MnCO₃−Au microspheres are beneficial for the realization of the direct electron transfer of Hb. Hb immobilized on the microspheres maintained its biological activity, showing a surface-controlled process with the heterogeneous electron transfer rate constant (k _s) of 2.63 s⁻¹. The fabricated biosensor displayed an excellent performance for the electrocatalytic reduction of H₂O₂. The linear range for the determination of H₂O₂ was from 0.06–40.0 μM with a detection limit of 0.015 µM (S/N = 3). The biosensor also exhibited high selectivity, good repeatability and long-term stability, which offers great potential for H₂O₂ detection in real sample analysis. (paper)