Nucleic Acids as Detection Tools

Abstract

The progress of biotechnology, especially towards nanobiotechnology, has been inspired from biological processes that have evolved over billions of years. Nucleic acids, long revered for their genetic coding properties, have now emerged as important materials for molecular diagnostic technologies. At the core of nucleic acid-based diagnostics is the fidelity of hybridization, a reversible thermodynamic process in which a nucleic acid molecule binds another nucleic acid molecule with the complementary sequence. This characteristic has been extensively explored in many areas of detection-oriented applications, to distinguish pathogenic species, to detect disease-related gene markers, to quantify the level of gene expression in cells and more. In addition to the ability to form helical structures, nucleic acids are also known to have the ability to perform more complex tasks such as enzymatic catalysis and molecular recognition (ligand binding). The first discovery in this arena was made in the early 1980s when some natural RNA molecules, now known as ribozymes, were found to exhibit catalytic properties reminiscent of protein enzymes [1,2]. Years later, an elegant technique known as ‘in vitro selection’ was invented and has since become a relatively routine process for engineering artificial DNA, RNA or modified nucleic acid molecules that can function as enzymes and receptors [3–6]. This has led to a colossal collection of functional nucleic acid sequences, many of which have been explored for bioanalytical applications. Our pursuit towards a better quality of life has generated an increasing demand for new tools and techniques to diagnose disease accurately or to examine environmental conditions. The ideal detection device and assay must offer great selectivity, excellent sensitivity, ease of use and low cost of production. Nucleic acids can satisfy these requirements due to the following assets: (1) specific Watson–Crick base pairing under a wide range of conditions, (2) high stability and long shelf-life, (3) low cost of synthesis and (4) excellent adaptability to external modifications such as radiolabels and fluorescent and colorimetric dyes.