A colloidal silver nanoparticles (CSNs) chemically modified electrode was prepared and its application to the electroanalysis of Cytochrome c (Cyt. c) was studied. The CSNs were prepared by reduction of AgNO3 with NaBH4, and were stabilized by oleate. They could be efficiently immobilized on the surface of a silver electrocle. The result showed that the CSNs could clearly enhance the electron transfer process between Cyt. c and the electrode compared with bulk silver electrode. Linear sweep voltammetric measurement of Cyt. c at the chemical modified electrode indicated that the oxidative peak current of Cyt. c was linear to its concentration ranging from 8.0 nmol L-1 to 3.0 mu mol L-1 with the calculated detection limit was about 2.6 nmol L-1. The direct electrochemistry of Cyt. c was also studied by cyclic voltammetry. (c) 2008 Elsevier Ltd. All rights reserved.