The kinetics of the change in mass related to the release from and deposition onto the cavities of a ferritin in the SWCNT nanocomposite by electrochemical redox reactions, and the effects of the SWCNT on the kinetics of the variation in mass of the ferritin nanocomposite were characterized using an electrochemical quartz crystal microbalance. The change in mass of reconstituted ferritin in the SWCNT nanocomposite shows reversible variation and stability of the ferritin/SWCNT nanocomposite on redox reactions was confirmed by using a coreless apoferritin and a Fe2+ chelating agent. The ferritin/SWCNT nanocomposite is a good candidate for applications based on electron transfer, such as biosensor, biobatteries and electrodes for biofuel cell. (C) 2010 Elsevier Ltd. All rights reserved.