Current Analytical Chemistry - Volume 7, Issue 1, 2011

This special issue is aimed at providing a recent update on the analytical mainly electroanalytical techniques used in the development of electrochemical DNA biosensors regarding DNA structure and DNA hybridization. It also addresses the significance of electroanalytical techniques as an alternative and even more as pioneering analytical techniques in the study of epigenetic DNA modification such as methylation. The focus is on the applicability of electroanalytical techniques as well as electrochemical biosensors in the detection of different DNA forms in biological samples. Distinguished scientists, from all over the world, have contributed in this special issue. Prof. Jan Labuda and his student provide an important review on electrochemical DNA biosensors and flow-through analysis. Prof. Gennady A. Evtugyn along with Prof. Tibor Hianik describe the role of layer-by-layer polyelectrolyte assembles involving DNA as a platform for DNA sensors. Prof. Miroslav Fojta and his colleagues present osmium tetroxide complexes as versatile tools for structure probing and electrochemical analysis of biopolymers. Prof. Elena Ferapontova critically discusses in an extensive review the role of electrochemical indicators for DNA electroanalysis. Prof. Arzum Erdem and her colleagues provide important information about the recent electrochemical biosensor technologies for monitoring of nucleic acid hybridization. Prof. Farukh Arjmand and her colleagues present a very well known electrochemical technique; Cyclic Voltammetry as an electrochemical approach to study metal-based potential antitumor drug-DNA interaction. Finally Prof. Zorka Stanic along with me describe the last decade of carbon paste electrodes in DNA electrochemistry. It was really an honour for me to be a guest editor in a special issue where all these distinguished scientists have contributed. I wish to thank them all for their excellent cooperation.

Process and quality control requires fast and reliable obtaining of results in all topics of chemical analysis. Flow-through analytical systems offer unique features and advantages, particularly regarding a possibility of automation of key steps of measurement in analytical chemistry. Principles of flow injection analysis (FIA) have been numerously utilized in connection with the detection by biosensors and bioassay. While the flow-through analytical systems are mostly reported for enzymatic biosensors, in this paper some principles of the detection with DNA biosensors and possibilities of their arrangement within a FIA scheme are reported.

The development of DNA-sensors has become significantly important in the past decades due to prospects of application in medicine, biotechnology and exploring fundamental problems related to cell biology and DNA functioning. Layer-by-layer (LbL) immobilization provides unique approach to the implementation of DNA into the surface sensing layers, a crucial step of DNA-sensor development. The review considers main aspects of LbL assembling in DNA-sensor development and application for the detection of complementary oligonucleotides and DNA damage assessment. Besides, electrostatic assembling due to stepwise accumulation of oppositely charged layers, various combinations of covalent binding and affine immobilization are also considered. The characteristics of DNA containing multilayers onto the solid support and the effect of the immobilization techniques and layers assembled on the performance of appropriate DNAsensors are summarized for different target analytes.

Osmium tetroxide complexes with nitrogenous ligands and analogous complexes of six-valent osmium proved excellent tools for selective labeling of biopolymers (nucleic acids, proteins and polysaccharides). Reactions of these species with target moieties within the biopolymer molecules (pyrimidine nucleobases, tryptophan residues or sugar moieties) are facile at physiological conditions and are in general structure-selective, allowing their application in DNA and protein structure probing. The modification products can be detected by a variety of widely accessible analytical techniques, including biochemical (enzymatic) approaches, immunoassays, chemical DNA sequencing, spectrophotometry and electrochemistry. Particularly the electrochemical techniques are promising for utilization in biosensors and routine bioassays due to the possibility of highly sensitive and selective detection of the labeled biopolymers adducts based on distinct electrochemical properties of the introduced osmium moieties. Utilization of the osmium tags in probing DNA structural transitions, sensing of DNA hybridization, damage and DNA methylation, labeling of peptides and proteins, probing accessibility of tryptophan residues in proteins and their complexes, and labeling of sugar moieties, are reviewed.

Electrochemical redox compounds, which can interact or bind with different affinities to single and double stranded DNA and thus are referred to as electrochemical hybridization indicators, represent a powerful and, along with this, simple tool for electrochemical genetic analysis. In this paper, general tendencies and recent advances in this field, including the modes of DNA-redox indicators interactions, approaches for their electrochemical analysis, and applications in electrochemical DNA assays are overviewed. This is a critical mini-review with 122 references.

Electrochemical biosensors have a key importance in many areas including clinical, biological, pharmaceutical, forensic, environmental and agricultural applications. They have the advantages of rapid, easy and low cost preparation allowing the localization of biocompound on electrodes of any size with independence of sample turbidity, high sensitivity and high selectivity. Electrochemical devices have attracted considerable interest in the development of DNA hybridization biosensors. They rely on the conversion of hybridization event into a direct electrochemical signal. Many efforts have been carried out in the detection of DNA hybridization for improving the stability, reproducibility and sensitivity. This review summarizes the advanced electrochemical methodologies involved in nucleic acid hybridization performed by using polymer technology, nanoparticles (NPs), magnetic particles, and carbon nanotubes (CNTs). The preparation of polymer modified electrodes especially including conducting polymers and their applications for DNA hybridization are given with the advantages of electrocatalysis, good electroactivity, high sensitivity and providing suitable matrix for DNA immobilization. The role of various nanomaterials in biosensors with the advantages of high surface area, fast heterogeneous electron transfer, excellent biocompatibility and enhanced signal with a good selectivity are presented. The combination of these techniques is also discussed in details.

The application of electrochemical measurements of the redox couples of metal-based antitumor potential drugs in the presence of DNA is a highly sensitive method due to the resemblance between the electrochemical and biological reactions. CV provides a useful complement to the other biophysical methods of investigations such as UV-visible spectroscopy and fluorescence studies. Since the redox active metal complexes are not amenable to such methods either due to weak absorption bands viz; forbidden d-d transitions or because of overlap of electronic transitions with those of DNA molecule, they can potentially be studied via voltammetric techniques. Equilibrium constant (K) for the interaction of the metal complexes with DNA can be obtained from shifts in peak potentials, and the number of base pair sites involved in binding through intercalative, electrostatic or hydrophobic interactions can be obtained from the dependence of current passed during oxidation or reduction of the bound species on the amount of added DNA. In this review, we primarily focus on the description of the DNA interaction with some potential metalbased antitumor drugs as investigated by cyclic voltammetry. In our laboratory, we have employed CV studies to validate the binding strength of a series of potential metal- based drugs with CT-DNA.

A great progress in the development of electrochemical carbon paste sensors for DNA hybridization and DNA damage achieved in recent years suggests that these sensors may soon become important tools in medicine and other areas of practical life of the 21st century. The article illustrates a growing number of applications of carbon electrodes in analytical chemistry. Various modifications of carbon pastes and carbon paste-based biosensors are mentioned. This review focuses on the current state of the DNA electrochemical carbon sensors with emphasis on recent advances, challenges and trends. It covers mainly publications which appeared during the period 1999-2009.