Facilitated electron transfer of hemoglobin embedded in nanosized Fe3O4 matrix based on paraffin impregnated graphite electrode and electrochemical catalysis for trichloroacetic acid

Nanosized Fe3O4, coated with acrylic acid copolymer approximately 5 nm in size, was synthesized and used for fabrication of hemoglobin (Hb) immobilized electrochemical sensor. Facilitated electron transfer (eT) of Hb embedded in the nanosized Fe3O4 solid matrix on paraffin impregnated graphite electrode (PIGE) was observed corresponding to Hb heme Fe(III)/Fe(II) conversion. A pair of stable and well-defined redox peaks at approximately -0.293 V vs. saturated calomel electrode was obtained at the Hb-Fe3O4 modified PIGE. It was found that nanosized Fe3O4 solid matrix could offer, a friendly platform to assemble Hb molecules and greatly enhance the eT in the absence of conventional mediators. The standard rate constant, k(s), was determined as 4.2 s(-1). Spectroscopic studies revealed that Hb retained the native-like structure in the nano-Fe3O4 solid matrix. Embedded Hb showed a great catalytic activity toward trichloroacetic acid (TCA) with 900 mV decrease in reduction overpotential. This was used for voltammetric determination of TCA with detection limit of approximately 0.116 mmol l(-1). (C) 2003 Elsevier Science B.V. All rights reserved.