An amperometric biosensor based on hemoglobin immobilized in poly(ε-caprolactone) film and its application

In this study, poly(epsilon-caprolactone) (PCL) was synthesized using the E-caprolactone (CL) monomer ring-opening polymerization. We demonstrated that the hemoglobin (Hb) entrapped in PCL film could retain its original conformation by FT-IR spectra. A pair of well-defined redox peaks with a formal potential (E-0') of about -0.38 V (vs. SCE) in a pH 7.0 phosphate buffer solution was obtained at the Hb-PCL film modified GC electrode. The dependence of E-0' on the pH of the buffer solution indicated that the conversion of heme, Fe(III)/Fe(II) was a reaction of one electron coupled to one proton. The apparent heterogeneous electron transfer rate constants (k(s)) of Hb confined to PCL was evaluated as (18.7 +/- 0.8) s(-1) according to Laviron's equation. The surface concentration (Gamma*) of the electroactive Hb in the PCL film was estimated to be (7.27 +/- 0.5 7) x 10(-11) mol cm(-2). The Hb-PCL film modified electrode was shown to be an excellent amperometric sensor for the detection of hydrogen peroxide. The linear range is from 2 to 30 mu M with a detection limit of 6.07 x 10(-6) M. The sensor was effectively testified by the determination of the hydrogen peroxide in eyedrops as real samples. (C) 2008 Elsevier B.V. All rights reserved.