Direct electrochemistry of horseradish peroxidase bonded on a conducting polymer modified glassy carbon electrode

Abstract

Direct electron transfer process of immobilized horseradish peroxidase (HRP) on a conducting polymer film, and its application as a biosensor for H 2O 2, were investigated by using electrochemical methods. The HRP was immobilized by covalent bonding between amino group of the HRP and carboxylic acid group of 5,2′:5′,2″-terthiophene-3′-carboxylic acid polymer (TCAP) which is present on a glassy carbon (GC). A pair of redox peaks attributed to the direct redox process of HRP immobilized on the biosensor electrode were observed at the HRP ∣ TCAP ∣ GC electrode in a 10 mM phosphate buffer solution (pH 7.4). The surface coverage of the HRP immobilized on TCAP ∣ GC was about 1.2×10 −12 mol cm −2 and the electron transfer rate ( ks) was determined to be 1.03 s −1. The HRP ∣ TCAP ∣ GC electrode acted as a sensor and displayed an excellent specific electrocatalytic response to the reduction of H 2O 2 without the aid of an electron transfer mediator. The calibration range of H 2O 2 was determined from 0.3–1.5 mM with a good linear relation.