End termination of commercial BDD electrodes with Sulphur and Nitrogen functionality for improved immobilisation of biomolecules.

Priscilla G. Baker ,  Euodia H. Hess ,  Tesfaye Waryo ,  Emmanuel I. Iwuoha 

University of Western Cape (UWC), Modderdam Road, Bellville, CAPE TOWN 7535, South Africa

Abstract

Commercial boron doped diamond (BDD) electrodes are terminated by hydrogen due to the chemical vapour deposition (CVD) process of and subsequent annealing in hydrogen atmosphere. For most applications in electrochemistry a surface activation procedure is required, which consists of anodic polarization in string acid solution, which reduces the hydrophobic character of the electrode surface. This is followed by cathodic pretreatment under the same experimental conditions but suitably negative voltage in order to enhance the electrochemical response and ensure reproducibility of voltammetric results (1, 2, 3). However, many other kinds of surface modification of BDD electrodes have been attempted, including dry and wet processes, such as thermal, chemical, photochemical plasma etching and electrochemical treatments (4, 5). We have already developed a number of novel conductive polymer platforms for the immobilisation of biomolecules and have demonstrated their electrochemistry and associated applications (6,7,8). In this paper we have concentrated our efforts specifically on the modification of commercial BDD electrodes to enhance its suitability for the immobilization of the integral membrane protein, cytochrome c oxidase, which is composed of several metal prosthetic sites. Immobilisation is proposed to occur through co-ordinate covalent bond formation between BDD electrodes that are S-terminated (or N-terminated) with the metal center of these molecules. In this way the protein is directly attached to the electrode surface and extensive wiring between the active metal centre of the protein and the electrode surface is circumvented. The efficiency of S- and N-termination of BDD electrodes by (i) electrochemical methods and (ii) UV activation was characterised by X-ray proton emission spectroscopy (XPS) and surface morphology was studied using scanning electron microscopy (SEM). The interfacial kinetics of the modified commercial BDD electrodes was studied by various electrochemical methods and will be highlighted in this paper. References: (1) Direct cytochrome c electrochemistry at boron-doped diamond electrodes, F. Marken, C.A. Paddon, D. Asogan, Electrochem. Commun., 4 (2002) 62. (2) V.A. Pedrosa, L. Codognoto, S.A.S. Machado, L.A. Avaca, J. Electroanal. Chem. 573 (2004) 11–18. (3) G.R. Salazar-Banda, L.S. Andrade, P.A.P. Nascente, P.S. Pizani, R.C. Rocha-Filho, L.A. Avaca, Electrochim. Acta 51(2006) 4612–4619. (4) D.A. Tryk, T. Kondo, A. Fujishima, in: A. Fujishima, Y. Einaga, T.N. Rao, D.A. Tryk (Eds.), Diamond Electrochemistry, Elsevier/BKC, Amsterdam/ Tokyo, 2005, Chapter 9. (5) T. Kondo, H. Ito, K. Kusakabe, K. Ohkawa, Y. Einaga, A. Fujishima, T. Kawai. Electrochimica Acta 52 (2007) 3841–3848. (6) J.H.O. Owino, O.A. Arotiba, N. Hendricks, E.A. Songa, N. Jahed, T.T. Waryo, R.F. Ngece, P.G.L. Baker , E.I. Iwuoha. Sensors 2008, 8, 8262-8274. (7) E.A. Songa, V.S. Somerset, T.T. Waryo, P.G.L. Baker, E.I. Iwuoha. Pure Appl. Chem., Vol. 81, No. 1, pp. 123–139, 2009. (8) P.M. Ndangili, T.T. Waryo, M. Muchindu, P.G.L. Baker, C. J. Ngila, E.I. Iwuoha. Electrochimica Acta (2009), doi.org/10.1016/j.electacta.2009.04.058

 

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Presentation: Keynote lecture at SMCBS'2009 International Workshop, by Priscilla G. Baker
See On-line Journal of SMCBS'2009 International Workshop

Submitted: 2009-08-18 14:02
Revised:   2009-09-19 09:30