We report for the first time a simple approach to fabricate an electrochemical DNA (E-DNA) biosensor by introducing the single-walled carbon nanotubes (SWNTs). The SWNTs combine with the electrochemical label (methyl blue, MB)-modified single-stranded DNA (ssDNA) probes to generate a nanomaterial-biomolecule composite, which functions as a signal amplification platform to facilitate the electron-transfer between the electrochemical label and the electrode. This SWNT-based E-DNA biosensor produces a high square wave voltammetry (SWV) signal in the absence of target DNA. In the presence of target DNA, the MB-labeled ssDNA probes are removed from the SWNT-modified electrode due to the formation of a double-stranded DNA (dsDNA), generating a relatively low SWV signal. This signal-off SWNT-based E-DNA biosensor exhibits improved sensitivity and large linear dynamic range with low detection limit; it can even distinguish 1-base mismatched target DNA. Further experiments demonstrate that the SWNT-based E-DNA biosensor is superior to the multi-walled carbon nanotube (MWNT)-based one for DNA detection. Moreover, the introduction of aptamer into the SWNT-based biosensor might be further extended to detect small biomolecules such as adenosine.
"The unique properties of carbon nanotubes (CNTs) have generated a tremendous amount of research for the development of novel technological applications. Recently, there has been a great interest in applying CNTs for the sensitive detection of biomolecules, such as glucose , cholesterol , cancer biomarkers , proteins , and DNA/RNA , because of their remarkable biomolecular recognition     . When such superior biomolecular recognition capabilities are utilized together with the unique physical properties of nanoscale CNTs, it could be developed for use as microarray biosensors, which provide an efficient biomolecule identification technique over traditional techniques, such as enzyme-linked immunosorbent assays (ELISAs) and Western blots, due to their ability of carrying out the multiplex detection of biomolecules on a single platform and minimal sample consumption   . "
[Show abstract][Hide abstract] ABSTRACT: To realize maskless functionalization of a carbon nanotubes (CNTs) dot array, a localized surface functionalization technology using an ultrafine atmospheric pressure plasma jet was developed. The plasma surface functionalization onto vertically aligned CNTs was carried out in two stages: pretreatment for activation of the CNT surface and posttreatment for surface functionalization. The experimental results of chemical derivatization with the fluorescent dye show that the CNT dot array was not only successfully functionalized with amino (–NH2) and carboxyl (–COOH) groups but also functionalized without any interference between functional groups. The success of maskless functionalization in the line pattern provides a means of a multifunctionalized CNT dot array with direct implications for future application of a microarray biosensor.
[Show abstract][Hide abstract] ABSTRACT: Due to the rapid response, the high sensitivity, the good selectivity and the experimental convenience of the electrochemical DNA biosensor, its applications have attracted broad interest.This article reviews electrochemical DNA biosensors and different methods proposed for their construction to overcome their limitations in selectivity and sensitivity. We also discuss their performance and future prospects.
[Show abstract][Hide abstract] ABSTRACT: Square wave voltammetry (SWV) has been widely used in the development of electrochemical sensors and biosensors in recent years due to its high selectivity and sensitivity. It is of great interest and importance to rapidly and sensitively detect disease-related biomarkers, environmental pollutants (e.g., heavy metals and other chemical contaminants), which are severely detrimental to human and animal life and the environment as a whole. Further, efficacious sensing is required for the detection of food resident contaminants (e.g., bacteria, viruses and parasites) and for the verification of the therapeutic ingredients of dietary supplements. Enzyme kinetics is another interesting domain that employs SWV as an effective analytical tool for the mechanistic study of enzyme reactions. The aim of this paper is to provide a comprehensive review of the electrochemical SWV method and its significant applications in sensing and biosensing spanning various fields such as diagnosis, environmental and food analysis and enzyme kinetics. The development of novel and improved electrode surfaces and nanomaterials introduces the possibility of sensors and biosensors that will exhibit even higher sensitivity, with SWV serving as an ideal methodology for its optimization. Concurrent with a better understanding of electrochemistry and life sciences, sensors and biosensors based on SWV have the potential to serve as next generation point-of-care diagnostic devices, as well as highly sensitive and selective detectors for food/environmental monitoring and enzyme studies.
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