Electroanalytical properties of haemoglobin in silica-nanocomposite ﬁlms electrogenerated on pyrolitic graphite electrode T. Rozhanchuk a , O. Tananaiko a, * , I. Mazurenko a , M. Etienne b , A. Walcarius b , V. Zaitsev a a Department of Analytical Chemistry, National Taras Shevchenko University, Volodymyrska 64, Kyiv 01601, Ukraine b Laboratoire de Chimie Physique et Microbiologie pour l’Environnement, UMR 7564, CNRS-Nancy University, 405 rue de Vandoeuvre, 54600 Villers-les-Nancy, France article info Article history: Received 21 May 2008 Received in revised form 4 September 2008 Accepted 6 October 2008 Available online 17 October 2008 Keywords: Haemoglobin Au nanoparticles Electrogenerated ﬁlm Sol–gel bioencapsulation Thin-ﬁlm electrode abstract Haemoglobin (Hb) modiﬁed electrochemical devices have been prepared by Hb encapsulation in silica sol–gel ﬁlms (SiO 2 ), which were generated by electro-assisted deposition onto pyrolitic graphite elec- trodes (PGEs). The stability and electrocatalytic activity of Hb entrapped into SiO 2 network was substan- tially enhanced in the presence of cationic surfactant (CTAB) and Au nanoparticles (Au-NPs). The composition of sol–gel synthesis medium, i.e., molar ratio of silica precursor to water, contents of Hb, CTAB and Au-NPs, as well as the conditions of electrogeneration had a great inﬂuence on the electrocat- alytic activity of Hb on PGE surface. The electrochemical response of the PGE modiﬁed with the compos- ite SiO 2 –Hb–CTAB–Au-NPs ﬁlm was found to vary linearly with the concentration of dissolved oxygen in solution and this was exploited to determine this analyte in the tap water with detection limit 0.12 mg L 1 . The electrocatalytic current of dissolved oxygen was also found to decrease in the presence of the antivirus drug––amino derivative of adamantane (rimantadine)––which opens the way to the determination of this drug with detection limit 0.3 mg L 1 using PGE modiﬁed with SiO 2 –Hb–CTAB– Au-NPs nanocomposite ﬁlm. Ó 2008 Elsevier B.V. All rights reserved. 1. Introduction Amperometric biosensors based on enzymes entrapped in silica matrices coated on solid electrode surfaces become increasingly popular as this way of biomolecule immobilization imparts high stability and good catalytic activity [1–3]. Sol–gel-derived silica- based materials are indeed attractive hosts for enzymes as they are chemically inert towards biomolecules and their three-dimen- sional structure does not restrict conformation mobility of the lat- est, so encapsulated biomolecules can retain their catalytic activity [4–6]. On the other hand, it was shown earlier that heme proteins such as haemoglobin (Hb) and myoglobin acquire peroxidase activity while immobilised [7,8] and haemoglobin-based ampero- metric biosensors were proposed for determination of various ana- lytes, including O 2 ,H 2 O 2 and NO  2 [9–11]. The detection scheme involved the catalytic reduction of these compounds on the Hb- modiﬁed electrodes. Another promising application of Hb-modi- ﬁed electrodes is the determination of some pharmaceuticals (e.g., antivirus or anticancer drugs) that are likely to interact with Hb. Examples are available for detection of Taxol and ribavirin using Hb-modiﬁed electrodes on the basis of a decrease in the cat- alytic current relative to O 2 reduction upon increasing the drug concentration [12,13]. Recently the method of electrodeposition was proposed to ob- tain thin sol–gel coatings on solid electrode surfaces, which was achieved via an electrochemical modulation of pH at the elec- trode/solution interface to promote geliﬁcation of the sol in a con- trolled way [14,15]. Electrodeposition method shows a few advantages comparing to classic spin-coating and dip-coating methods, particularly the ability to control the thickness of the ﬁlms, greater porosity and simplicity of procedure [15]. This was notably applied to get organically-functionalized silica thin ﬁlms on electrodes [16–18] or well-structured and oriented deposits [19,20], which can be applied as sensitive nano-layers with good analytical performance [21,22]. Very recently, we have demon- strated that such an electro-assisted generation approach can be extremely useful for encapsulation of biomolecules, i.e., Hb and glucose oxidase, in silica thin ﬁlms deposited on glassy carbon electrodes [23]. The encapsulated enzymes retained their catalytic activity without additional use of mediators. Still the problem of the stability of immobilised proteins was not fully solved, giving notably rise to signiﬁcant decrease in the analytical signal with time, what we have tried to circumvent in the present study by the use of surfactant and/or nanoparticles additives. The addition of cationic surfactant (for example cetyltrimethyl- ammonium bromide, CTAB) at CMC and higher level as template agent into silica sol permits to obtain well-structured porous mate- rials [24,25]. Surfactants indeed improve the properties of sol–gel silica derived materials where encapsulated organic molecules are 0022-0728/$ - see front matter Ó 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.jelechem.2008.10.003 * Corresponding author. Tel.: +38 0 44 239 34 44; fax: +38 0 44 239 33 45. E-mail address: nadzhafova@univ.kiev.ua (O. Tananaiko). Journal of Electroanalytical Chemistry 625 (2009) 33–39 Contents lists available at ScienceDirect Journal of Electroanalytical Chemistry journal homepage: www.elsevier.com/locate/jelechem