This paper investigates the effect of silver nanoparticles on the electron transfer at bio-functionalized gold electrode interfaces. In its first part, it describes synthesis of silver nanoparticles (Ag-NP) and their bioconjugation with biotin or avidin. Then, it presents modification of gold electrodes by self-assembled monolayer of mercaptopropionic acid (MPA) and subsequent crosslinking of biotin or avidin. Finally, the Ag-NP bioconjugated respectively with avidin or biotin were anchored via biorecognition on these layers. The stepwise electrode modification was confirmed by quartz crystal microbalance (QCM) and changes of interfacial electron transfer process were examined by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) with [Fe(CN)(6)](3-/4-) redox probe. For modified electrodes without Ag-NP, CV present high differences between anodic and cathodic peaks potentials (Delta E-p = 205 and 105 mV) and high charge transfer resistance (R-ct = 8000 and 612 Omega) are measured. On the other hand, modified electrodes with Ag-NP exhibit smaller Delta E-p (80 mV for both) and R-ct (377 and 398 Omega). This decrease in charge transfer resistance when the last layer of modified electrode contains Ag-NP indicates that silver nanoparticles enhance the electron transfer through the organic layer of modified gold electrode. (C) 2013 Elsevier B.V. All rights reserved.