A DNA-Cu(II) complex was effectively utilized as a novel electrocatalyst for an H2O2-sensing electrode. The DNA-Cu(II) complex was immobilized onto the surface of a glassy carbon (GC) electrode by polyion complex formation with poly(allylamine) (PAA). Cyclic voltammetry revealed that the copper ion embedded in the DNA/PAA layer exhibited a pair of well-defined redox peaks which is due to the Cu(II)/Cu(I) redox couple. The resulting DNA-Cu(II)/PAA/GC electrode showed excellent electrocatalytic activity for H2O2 reduction. The amperometric response to H2O2 obtained at -0.2 V (vs. Ag\AgCl) was rapid and highly sensitive. A calibration curve obtained in air-saturated buffer (pH 5) was linear in the concentration range from 0.1 to 135 muM with a detection limit of 0.05 muM (S/N = ca. 3). Moreover, this sensor showed long term-storage stability of more than 30 days under dry conditions 4 degreesC. (C) 2004 Elsevier B.V. All rights reserved.