Enhanced biosensing performance of mesoporous SnO2 multilayer film in interfacing hemoglobin

Through alternative adsorption of dextran sulfate (DS) and mesoporous SnO2 (Meso-SnO2), {Meso-SnO2/DS}n films were constructed and applied for the immobilization of hemoglobin (Hb). For comparison, the same-sized non-mesoporous SnO2 nanopraticles (Nonmeso-SnO2) based films were also prepared. Thus-formed films were characterized by many techniques in detail. The electrochemical impedance spectroscopy (EIS, using ferricyanide/ferrocyanide as a redox probe) experiments confirmed the charge transfer resistance increased linearly with the number of Meso-SnO2/DS bilayers, which was smaller than that of Nonmeso-SnO2/DS bilayers. Further EIS, UV-vis and AFM experiments indicate that Meso-SnO2/DS film exhibit enhanced immobilization ability of Hb with favorable orientation in comparison with that of Nonmeso-SnO2/DS film. The adsorbed Hb at Meso-SnO2/DS film showed a good direct electron transfer behavior with the heterogeneous electron transfer rate constant (ks) of 8.89 +/-0.32 s(-1), and excellent electrocatalysis to the reduction of O2 and H2O2 in pH 7.0 buffers.