The development of cobalt(II) phthalocyanine-cobalt(II) tetra(5-phenoxy-10,15,20-triphenylporphyrin), (CoPc-(CoTPP)(4)) pentamer as a novel redox mediator for amperometric enzyme electrode sensitive to glucose is described. A glassy carbon electrode (GCE) was first modified with the pentamer, then followed by the immobilization onto the GCE-CoPc-(CoTPP)4 with glucose oxidase (GOx) through cross-linking with glutaraldehyde in the presence of bovine serum albumin (BSA) and Nafion (R) cation-exchange polymer. The proposed biosensor displayed good amperometric respose charateristics to glucose in pH 7.0 PBS solution; such as low overpotentials (+400mV versus Ag vertical bar AgCl), very fast amperometric response time (similar to 5 s), linear concentration range extended up to 11 mM, with 10 mu M detection limit. The biosensor exhibited electrochemical Michaelis-Menten kinetics and showed an average apparent Michaelis-Menten constant (K'(M)) of 14.91 +/- 0.46 mM over a storage period of 2 weeks. (c) 2006 Elsevier Ltd. All rights reserved.