Review A review on the electrochemical biosensors for determination of microRNAs Ezat Hamidi-Asl a,b,n , Ilaria Palchetti b , Ehteram Hasheminejad a , Marco Mascini b a Eletroanalytical Chemistry Research Laboratory, Department of Analytical Chemistry, Faculty of Chemistry, University of Mazandaran, Babolsar, Iran b Università degli Studi di Firenze, Dipartimento di Chimica, Via della Lastruccia 3, 50019 Sesto Fiorentino, Italy article info Article history: Received 11 December 2012 Received in revised form 22 March 2013 Accepted 26 March 2013 Available online 17 April 2013 Keywords: MicroRNAs Electrochemistry Biosensors abstract MicroRNAs (miRNAs) are a family of non-protein-coding, endogenous, small RNAs. They are a group of gene regulators that function mainly by binding the 3′ untranslated regions of specific target messenger RNA (mRNA) leading to gene inactivation by repression of mRNA transcription or induction of mRNA. Mature miRNAs are short molecules approximately 22 nucleotides in length. They regulate a wide range of biological functions from cell proliferation and death to cancer progression. Cellular miRNA expression levels can be used as biomarkers for the onset of disease states and in gene therapy for genetic disorders. Methods for detection of miRNA mainly include northern blotting, microarray, polymerase chain reaction (PCR). This review focuses on the use of electrochemical biosensors for the detection of microRNA. & 2013 Elsevier B.V. All rights reserved. Contents 1. Introduction ......................................................................................................... 74 1.1. RNA ......................................................................................................... 74 1.2. MicroRNA ..................................................................................................... 75 1.2.1. What is the relation between miRNA and non-coding RNAs?..................................................... 75 1.2.2. How many exactly are miRNA genes in the body? ............................................................. 75 1.2.3. What is the role of miRNAs in diseases? ..................................................................... 75 2. Difficulties in miRNA detection.......................................................................................... 75 3. Current detection methods ............................................................................................. 75 4. Electrochemical approaches ............................................................................................ 76 4.1. Nano materials................................................................................................. 76 4.1.1. Nanoparticles ........................................................................................... 76 4.1.2. Nanowires ............................................................................................. 76 4.2. Enzymes ...................................................................................................... 77 4.3. Electroactive complexes ......................................................................................... 79 4.4. Electrocatalytic oxidation of guanine ............................................................................... 81 5. Conclusions ......................................................................................................... 82 References .............................................................................................................. 82 1. Introduction A biosensor is a device incorporating a molecular recognition element associated with a physicochemical transducer. Transducing systems may be optical, electrochemical, thermometric, piezoelectric, micromechanical or magnetic. Materials that can be used as recogni- tion elements consist of proteins, tissues, cells, enzymes, nucleic acids etc. [1]. 1.1. RNA RNA, Ribonucleic acid, is one of the three major macromole- cules (along with DNA and proteins) in the body that are essential to all known forms of life. Like DNA, RNA is made up of a long Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/talanta Talanta 0039-9140/$ - see front matter & 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.talanta.2013.03.061 n Corresponding author at: Eletroanalytical Chemistry Research Laboratory, Department of Analytical Chemistry, Faculty of Chemistry, University of Mazandaran, Babolsar, Iran. Tel.: +98 112 5342392; fax: +98 112 5342350. E-mail addresses: ehamidiasl@umz.ac.ir, ehamidiasl@yahoo.com (E. Hamidi-Asl). Talanta 115 (2013) 74–83