19 Mater. Res. Soc. Symp. Proc. Vol. 1793 © 2015 Materials Research Society DOI: 10.1557/opl.2015.671 Breast cancer detection using charge sensors coupled to DNA monolayer Marina R. Batistuti 1 and Marcelo Mulato 1 and Paulo R. Bueno 2 1 Departamento de Física, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, 14040-901 Ribeirão Preto, Sao Paulo, Brazil 2 Instituto de Química, Universidade Estadual Paulista, CP 355, 14800-900, Araraquara, São Paulo, Brazil ABSTRACT We report the development of a label-free biosensors based on DNA hybridization, using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). This study uses DNA sequences based on microRNA related with breast cancer. The biosensor was fabricated by immobilizing a self-assembled monolayer of single-stranded 23-mer oligonucleotide ( ss DNA) via a thiol linker on gold work electrodes. Residual binding places were filled with 6 - mercaptohexanol (MCH). The electrode was electrochemicaly characterized in the presence of a redox system ferri/ferrocyanide. Different concentrations of complementary DNA sequence for hybridization were incubated; an increase of charge transfer resistance (R ct ) was observed, used as sensor parameter and correlated with concentrations of complementary DNA sequence. A debate was presented on the effect of the MgCl 2 influence on ss DNA immobilization solution. INTRODUCTION The development of DNA biosensors has increased over the past years motivated by applications in many fields as DNA diagnostics, gene analysis and forensic applications [1]. For example, detection of genetic mutations at the molecular level opens up the possibility of performing diagnostics before symptoms of a disease appears. DNA detection systems based on hybridization between ss DNA immobilized and its complementary probe are largely reported. The signal transduction of DNA hybridization can be measured by fluorescence [2], piezoelectric [3], surface Plasmon resonance spectroscopy [4], and electrochemical techniques [5]. Among the existing techniques, electrochemical DNA biosensors show an exceptional development in recent years [1,6-7]. MicroRNAs (miRNAs) are small sequences of RNA over 22-mer that can regulate a wide range of cellular processes at the post-transcriptional level. Since its discovery, there is an interest to study their roles in basic biological processes and their expression levels in human cancers [8]. The quantitative miRNA detection is fundamental for biological studies and diagnostic purposes [9,10]. However, RNA is not stable as DNA. Removal of the 2′-hydroxyl group from RNA to form DNA results in a backbone that is less susceptible to cleavage by hydrolysis and thus enables more-stable storage of genetic information. Similarly, a DNA biosensor is more stable than RNA.