Direct electron transfer and electrocatalysis of hemoglobin in layer-by-layer films assembled with Al-MSU-S particles

In this paper, layer-by-layer (LBL) {MSU/Hb}_n/PDDA films assembled by alternate adsorption of positively charged hemoglobin (Hb) and negatively charged mesoporous molecular sieves of Al-MSU-S onto a glassy carbon electrode (GCE) were reported. Al-MSU-S was synthesized by the precursor of zeolite Y and ionic liquids 1-hexadecane-3-methylimidazolium bromide (CMIMB) as a template in basic medium. It exhibited larger pore diameter, pore volume and surface area. Direct electrochemical and electrocatalytic properties of Hb in these layer-by-layer films were investigated. A pair of well-defined nearly reversible cyclic voltammetric peaks was observed and the formal potential of the heme Fe^III/Fe^II redox couple was found to be -0.295 V (vs. SCE). The influences of layer's number and the pH of the external solution to the electron transfer behavior of Hb in {MSU/Hb}_n/PDDA films were also estimated by cyclic voltammetry and a set of optimized conditions for film fabrication was inferred. The hemoglobin in{MSU/Hb}_n/PDDA films displayed a good electrocatalytic activity to the reduction of hydrogen peroxide, which had linear current responses from 1.0 × 10^-6 to 1.86 × 10^-4 mol/L with the detection limit of 5.0 × 10^-7 mol/L (S/N = 3). The apparent Michaeli-Menten constant (K_m ^app) was 0.368 mmol/L. Thus, this methodology shows potential application of the preparation of third-generation biosensors.