Biosensors and Bioelectronics 26 (2011) 3864–3869 Contents lists available at ScienceDirect Biosensors and Bioelectronics journal homepage: www.elsevier.com/locate/bios SiC nanoparticles-modified glassy carbon electrodes for simultaneous determination of purine and pyrimidine DNA bases Raouf Ghavami a,∗ , Abdollah Salimi a,b , Aso Navaee a a Department of Chemistry, Faculty of Science, University of Kurdistan, P.O. Box 416, Sanandaj, Iran b Research Center for Nanotechnology, University of Kurdistan, P.O. Box 416, Sanandaj, Iran article info Article history: Received 5 January 2011 Received in revised form 24 February 2011 Accepted 28 February 2011 Available online 5 March 2011 Keywords: Guanine Adenine Thymine Cytosine DNA Silicon carbide Nanoparticles Differential pulse voltammetry Simultaneous determination abstract For the first time a novel and simple electrochemical method was used for simultaneous detection of DNA bases (guanine, adenine, thymine and cytosine) without any pretreatment or separation process. Glassy carbon electrode modified with silicon carbide nanoparticles (SiCNP/GC), have been used for electrocatalytic oxidation of purine (guanine and adenine) and pyrimidine bases (thymine and cyto- sine) nucleotides. Field emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM) techniques were used to examine the structure of the SiCNP/GC modified electrode. The modified electrode shows excellent electrocatalytic activity toward guanine, adenine, thymine and cytosine. Differential pulse voltammetry (DPV) was proposed for simultaneous determination of four DNA bases. The effects of different parameters such as the thickness of SiC layer, pulse amplitude, scan rate, supporting electrolyte composition and pH were optimized to obtain the best peak potential sepa- ration and higher sensitivity. Detection limit, sensitivity and linear concentration range of the modified electrode toward proposed analytes were calculated for, guanine, adenine, thymine and cytosine, respec- tively. As shown this sensor can be used for nanomolar or micromolar detection of different DNA bases simultaneously or individually. This sensor also exhibits good stability, reproducibility and long lifetime. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Deoxyribonucleic acid (DNA) is an important substance that plays a crucial role in storage of genetic information and protein biosynthesis. DNA is a linear polymer that is made up of nucleotide units. This molecule has a three-dimensional double-helix struc- ture constituted by two chains, running in opposite directions, of polydeoxyribonucleotides, which are coiled around a common axis by purine and pyrimidine nucleobases. The two complementary pairs of nucleobases, adenine (A) with thymine (T) and cytosine (C) with guanine (G), have long been considered the key to DNA’s stability, replication, and capacity for information storage, with the hydrogen bonds between them playing an integral role (Guckian et al., 1998; Schweitzer and Kool, 1994; O’Neill et al., 2002). In recent years researchers have begun to probe the importance of these hydrogen bonds and other factors contributing to DNA’s intriguing characteristics by replacing base pairs with non-natural analogs (Kool, 2001; Dzantiev et al., 2001; Guckian et al., 2000). The abnormal changes of bases in organisms suggest the deficiency and mutation of the immunity system and may indicate the presence ∗ Corresponding author. Tel.: +98 871 662 4133; fax: +98 871 662 4133. E-mail addresses: rghavami2000@yahoo.com, rghavami@uok.ac.ir (R. Ghavami). of various diseases (Bartlett, 2008; Halliwell and Gutteridge, 1999; Valko et al., 2004; Loft et al., 1992). The average concentration of purines and pyrimidines in plasma and other extracellular fluids is generally in the range of 0.4–6 M; these values are usually lower than corresponding intracellular concentrations (Traut, 1994 and references therein). Therefore, development of simple and accurate analytical methods for individual or simultaneous determination of DNA bases has great significance in bioscience and clinical diagnosis. Most methods for the determination of individual purine and pyrimidine derivatives are based on absorption of ultraviolet light (Ts’o, 1974). Voltammetric methods are practically suited for the analysis of purine and pyrimidine due to the advantages including high sensitivity and selectivity, fast response, low cost and ultra small sample volumes. The electrochemical detection of these sub- stances in aqueous solution is generally based on electroreduction or electrooxidation of purine bases at a mercury electrode (Palecek, 1983, 1996), or electrooxidation at gold (Pang et al., 1995) copper (Singhal and Kuhr, 1997) highly boron-doped diamond (Ivandini et al., 2007), glassy carbon (Nakahara et al., 1992; Chen et al., 2008; Oliveira-Brett and Matysik, 1997; Oliveira-Brett et al., 2004) or pyrolytic graphite (Wang et al., 1996) electrodes. Although different modified electrodes have been used for electrocatalytic oxidation of purine bases, more of them have been used for individual or simul- 0956-5663/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.bios.2011.02.048