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

In this study, poly(ɛ-caprolactone) (PCL) was synthesized using the ɛ-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 (E0′)(E0′) 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 E0′E0′ 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 (ks) of Hb confined to PCL was evaluated as (18.7 ± 0.8) s−1 according to Laviron's equation. The surface concentration (Γ*) of the electroactive Hb in the PCL film was estimated to be (7.27 ± 0.57) × 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 μM with a detection limit of 6.07 × 10−6 M. The sensor was effectively testified by the determination of the hydrogen peroxide in eyedrops as real samples.