Fundamental studies of the cytochrome c immobilization by the potential cycling method on nanometer-scale nickel oxide surfaces Abdolmajid Bayandori Moghaddam a , Mohammad Reza Ganjali a, ⁎ , Rassoul Dinarvand b , Ali Akbar Saboury c , Taherehsadat Razavi a , Ali Akbar Moosavi-Movahedi c , Parviz Norouzi a a Centerof Excellence in Electrochemistry, Faculty of Chemistry, University of Tehran, P. O. Box: 14155-6455, Tehran, Iran b Medical Nanotechnology Research Centre, Medical Sciences/ University of Tehran, Tehran, P.O. Box 14155-6451, Iran c Institute of Biochemistry and Biophysics, University of Tehran, Tehran, Iran Received 12 April 2007; received in revised form 13 June 2007; accepted 14 June 2007 Available online 22 June 2007 Abstract This work describes the performance of cytochrome c/nickel oxide nanoparticles/glassy carbon electrode, prepared by the electrochemical deposition of the nickel oxide nanoparticles (NiO NPs) on the glassy carbon (GC) electrode surface and the cytochrome c immobilization on the nickel oxide nanoparticle surfaces. An extensive sample examination with the help of the SEM and AFM presented the existence of different geometrical shapes of the nickel oxide particles. These geometrical structures could lead to the better immobilization of proteins on their surfaces. The resulting electrode displayed an excellent behavior for the redox of the cytochrome c. Also, the resulting heme protein exhibited a direct electrical contact with the electrode because of the structural alignment of the heme protein on the nanometer-scale nickel oxide surfaces. This method could be suitable for applications to nanofabricated devices. In the end, it was concluded that the cytochrome c could be tethered to the nanometer-scale nickel oxide surfaces. © 2007 Elsevier B.V. All rights reserved. Keywords: Cytochrome c; Atomic Force Microscopy; Scanning Electron Microscopy; Nanoparticle; Nickel oxide; Nanoelectrochemistry; Bioelectrochemistry 1. Introduction Bioelectrochemistry is an interdisciplinary field, which combines biotechnology with the electrochemical discipline. This field started to attract the researchers' attention when the existing resemblance between the electrochemical and biological reactions became evident. In fact, it was realized that the oxidation mechanisms on the electrode and in the body share similar principles. On the other hand, the appearance of nanotechnology was opening a new entrance for the performance of this field. Subsequently, it was obvious that the essential coordination of these scientific branches could lead to fruitful findings. As far as nano-materials are concerned, they offer attractive properties and they have opened a new entrance for new electrodes in the field of electrochemical applications [1]. The nano-scale effects in the catalytic properties of gold particles are well-known chemically inert. Gold turns catalytically active when the particle size is below 3–4 nm [2,3]. Electrodes with nanometer dimensions provide exciting new tools for electro- chemical studies. The small dimensions lead to a high current density on the electrode surface, allowing the study of the fast heterogeneous electron transfer kinetics, the molecular interac- tions and the mass transport in the nanometer regime [4]. The existence of nano-size effects offers a new possibility to control reactivity by controlling the particle size. Exploiting the small dimensions of nanoelectrodes may allow innovative biological applications by means of entering local cellular environments and ultimately measuring the activity of a single redox-enzyme coupled to a nanoelectrode. Regarding the fundamental investigations of the biological redox reaction mechanism and the development of biosensors and bioelectronic devices, the achievement of an interface between the prosthetic groups of immobilized proteins/enzymes Biophysical Chemistry 129 (2007) 259 – 268 http://www.elsevier.com/locate/biophyschem ⁎ Corresponding author. Tel.: +98 21 61112788; fax: +98 21 66405141. E-mail address: Ganjali@khayam.ut.ac.ir (M.R. Ganjali). 0301-4622/$ - see front matter © 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.bpc.2007.06.006