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

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 μM to 0.16 mM for H2O2 and 1.5 μM to 0.12 mM for nitrite as well as the detection limits of 0.03 μM for H2O2 and 0.29 μM 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.

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► Layer-by-layer (LBL) film of core–shell nanoparticles (Fe3O4@Pt NPs) and hemoglobin (Hb) was applied for biosensing.
► Fe3O4@Pt in the LBL film can greatly improve the direct electron exchange between Hb moleculars and the electrode.
► The fabricated LBL film displayed excellent response for the detection of H2O2 and nitrite.
► Electrochemical and catalytical activity of LBL film can be adjusted by controlling the number of bilayers.