Electrochimica Acta 82 (2012) 137–142 Contents lists available at SciVerse ScienceDirect Electrochimica Acta jou rn al hom epa ge: www.elsevier.com/locate/electacta Electrochemical sensing of label free DNA hybridization related to breast cancer 1 gene at disposable sensor platforms modified with single walled carbon nanotubes Chen-zhong Li a,b , Hakan Karadeniz a , Ece Canavar a , Arzum Erdem a,∗ a Ege University, Faculty of Pharmacy, Analytical Chemistry Department, 35100 Izmir, Turkey b Nanobioengineering/Bioelectronics Lab, Department of Biomedical Engineering, Florida International University, 10555 West Flagler Street, Miami, FL, USA a r t i c l e i n f o Article history: Received 18 October 2011 Received in revised form 18 April 2012 Accepted 16 May 2012 Available online 7 June 2012 Keywords: Screen printed graphite electrode Carbon nanotubes DNA hybridization Electrochemical sensor BRCA1 Electrochemical impedance spectroscopy a b s t r a c t The electrochemical monitoring of DNA hybridization related to specific sequences on breast cancer 1 (BRCA1) DNA by using singlewalled carbon nanotube (SWCNT) based screen printed graphite electrodes (SPEs) was performed in this study. After the microscopic characterization of SWCNT-SPE, the optimiza- tion of assay was studied. The development of screen printing process combined with nanomaterial based disposable sensor technology with sensitivity, selectivity and reproducibility, has a great opportunity for DNA detection using differential pulse voltammetry (DPV) by measuring the guanine oxidation signal observed at +1.00 V in the presence of DNA hybridization between BRCA1 probe and its complemen- tary target. The detection limit estimated for signal to noise ratio = 3 corresponds to 378.52 nM target concentration in the 40 L samples. The voltammetric results on BRCA1 DNA hybridization were also complemented with electrochemical impedance spectroscopy (EIS). © 2012 Elsevier Ltd. All rights reserved. 1. Introduction The study of the genetic bases of complex diseases, such as diabetes, heart disease, and cancer, requires the accurate identi- fication of genomic variations and genetic mutations at different levels of resolution. During the last few years, the development of DNA based sensing systems such as DNA chips, biochips, genechips, biosensors and DNA arrays has been the main focus of many research groups and high technology companies. A basic DNA biosensor is designed by the immobilization of a single stranded oligonucleotide on sensing substrates to recog- nize its complementary (target) DNA sequence via hybridization. The hybridization event is then converted into a readable signal by the transducers [1–9]. Common transducing elements include opti- cal, electrochemical, surface plasmon resonance or mass-sensitive elements which can generate readable light, current or frequency signals. Recently, the miniaturized electrochemical biosensors have attracted substantial research efforts and great attention, especially for applications which require direct real time monitoring, short analysis duration, and a low detection limit [10,11]. However, most previously reported biosensing systems have not been implemented in a chip-based platform and lack the ∗ Corresponding author. Tel.: +90 232 311 5131; fax: +90 232 388 5258. E-mail address: arzum.erdem@ege.edu.tr (A. Erdem). specificity for detecting different types of DNA mutants. In addition, a complex labeling process is generally requried in the previ- ous publications, in which during readout, the amount of label is detected and assumed to correspond to the number of analytes [8,9,12]. Among various aspects of DNA sequence assay, the most chal- lenging and demanding one is the rapid and reliable detection of DNA mutants. Recent genome-wide association studies have led to the identification of numerous polymorphisms associated with increased risk for cancers. Breast cancer 1 (BRCA1) DNA mutant detection in disease-related gene fragments is critical for genetic research and clinical diagnosis. For example, more than 1200 dif- ferent single nucleotide polymorphisms (SNPs) have been found in BRCA1 associated with breast cancers. Breast cancer 1, a tumor sup- pressor gene on chromosome 17 at band 21, 38.449.840 to base pair 38.530.994, was identified in 1994 based on its linkage to hereditary breast and ovarian cancer syndromes. Mutations in BRCA1 gene are responsible for approximately 40% of inherited breast cancers and more than 80% of inherited breast and ovarian cancers [13]. Analy- sis of BRCA1 gene mutations may permit identification of a subset of breast cancer patients who, despite the lack of conventional indi- cators of poor prognosis, are at high risk of early recurrence and death. In aspects of electrochemical detection of DNA hybridiza- tion related to BRCA1 breast-cancer gene, there have been many reports presenting a very sensitive and selective electrochemical 0013-4686/$ – see front matter © 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.electacta.2012.05.057