An electrochemical sensing platform was developed based on Fe3O4 nanoparticles/multiwalled carbon nanotubes (MWNTs) nanocomposite modified glassy carbon electrode. Magnetic Fe3O4 nanoparticles was deposited by the chemical coprecipitation of Fe2+ and Fe3+ in the presence of MWNTs in an alkaline solution. The resulting magnetic nanocomposite brings new capabilities for electrochemical devices by combining the advantages of MWNTs and Fe3O4 nanoparticles and provides an alternative way for loading MWNTs on electrodes. Transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM) and vibrating sample magnetometry (VSM) techniques have been utilized for the characterization of the synthesized Fe3O4/MWNTs nanocomposite. The cyclic voltammetry and chronoamperometric experiments were used for studying the behavior of this modified electrode towards electrooxidation of the reduced form of nicotinamide cofactor (NADH). The electrode exhibited excellent performances in that it led to a substantial decrease in the overpotential of electrochemical NADH oxidation. Iron oxide plays a significant role as a catalyst for NADH oxidation and the reaction occurs at +0.00V (vs. Ag/AgCl). The method of the sensor construction is very simple and the sensor performed well, giving high sensitivity, high stability,and a broad detection range. Such ability to promote the electron transfer between NADH and the electrode suggested a new promising biocompatible platform for development of dehydrogenase-based amperometric biosensors. Lactate dehydrogenase (LDH) as a modelenzyme could be covalently immobilized using well established EDC/NHS chemistry onto Fe3O4/MWNTs nanocomposite. The Fe3O4/MWNTs/LDH modified GC electrode showed rapid and highly sensitive amperometric response to lactate with acceptable preparation reproducibility and excellent stability.
