Nanostructured biosensors built with layer-by-layer electrostatic assembly of hemoglobin and Fe3O4@Pt nanoparticles

a b s t r a c t This paper reports layer-by-layer (LBL) films fabricated with hemoglobin and core–shell nanoparticles with Fe3O4 as the core covered by Pt (Fe3O4@Pt) and their applications in biosensing. The characterization of {Hb/Fe3O4@Pt}n LBL films at different layers revealed that the formation of films is step-by-step and uniform. Meanwhile, at glassy carbon electrodes modified with {Hb/Fe3O4@Pt}n film at different layers there was a pair of well-defined and nearly reversible peaks in cyclic voltammetry (CV). CV results indicated that the electroactivity of the structure with four bilayers was the best. The {Hb/Fe3O4@Pt}4 film modified electrode could be used to detect H2O2 and nitrite with the linear range from 0.125 M to 0.16 mM for H2O2 and 1.5 M to 0.12 mM for nitrite as well as the detection limits of 0.03 M for H2O2 and 0.29 M for nitrite (S/N = 3). The biosensors also exhibited good reproducibility, high selectivity, and long-term stability. Our investigation showed that the strategy taking advantages of Fe3O4@Pt and LBL assembly is ideal for direct electrochemistry of redox proteins as well as the sensitive and stable mediator-free biosensors.