Increasing the Sensitivity of Electrochemical DNA Detection by a Micropillar-Structured Biosensing Surface (original) (raw)
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Electrochemical Patterning and Detection of DNA Arrays on a Two-Electrode Platform
Journal of the American Chemical Society, 2013
We report a novel method of DNA array formation that is electrochemically formed and addressed with a two-electrode platform. Electrochemical activation of a copper catalyst, patterned with one electrode, enables precise placement of multiple sequences of DNA onto a second electrode surface. The two-electrode patterning and detection platform allows for both spatial resolution of the patterned DNA array and optimization of detection through DNA-mediated charge transport with electrocatalysis. This two-electrode platform has been used to form arrays that enable differentiation between well-matched and mismatched sequences, the detection of TATA-binding protein, and sequence-selective DNA hybridization. Nucleic acid sensors are critical for the detection of many biological markers of disease. Although fluorescence-based hybridization arrays have proven useful for high-throughput screening applications, 1,2 they have not shown utility for bench-top clinical diagnostics. Electrochemical assays based on DNA-mediated charge transport (DNA CT) are well suited for point-of-care applications; they require only simple electronic instrumentation and do not require stringent hybridization procedures to report on mutations, protein binding, as well as other π-stack perturbations. 3-5
Surface techniques for an electrochemical DNA biosensor
Biosensors and Bioelectronics, 1997
The surface of platinum electrodes was modified by a technique that provides binding sites for covalent site-specific immobilization of DNA. In the course of immobilization certain substances such as thiols, iodine and iodide were brought in contact with the metal. The effect on the electrochemical characteristics of thin film platinum electrodes caused by chemisorption of these substances was investigated. Voltage pulsing was very effective in restoring the electrocatalytical properties of the electrodes.
An Electrochemical DNA Biosensor Developed on a
2008
An electrochemical DNA nanobiosensor was prepared by immobilization of a 20mer thiolated probe DNA on electro-deposited generation 4 (G4) poly(propyleneimine) dendrimer (PPI) doped with gold nanoparticles (AuNP) as platform, on a glassy carbon electrode (GCE). Field emission scanning electron microscopy results confirmed the co-deposition of PPI (which was linked to the carbon electrode surface by C-N covalent bonds) and AuNP ca 60 nm. Voltammetric interrogations showed that the platform (GCE/PPI-AuNP) was conducting and exhibited reversible electrochemistry (E°′ = 235 mV) in pH 7.2 phosphate buffer saline solution (PBS) due to the PPI component. The redox chemistry of PPI was pH dependent and involves a two electron, one proton process, as interpreted from a 28 mV/pH value obtained from pH studies. The charge transfer resistance (Rct) from the electrochemical impedance spectroscopy (EIS) profiles of GCE/PPI-AuNP monitored with ferro/ferricyanide (Fe(CN)63-/4-) redox probe, decreased by 81% compared to bare GCE. The conductivity (in PBS) and reduced Rct (in Fe(CN)63-/4-) values confirmed PPI-AuNP as a suitable electron transfer mediator platform for voltammetric and impedimetric DNA biosensor. The DNA probe was effectively wired onto the GCE/PPI-AuNP via Au-S linkage and electrostatic interactions. The nanobiosensor responses to target DNA which gave a dynamic linear range of 0.01 - 5 nM in PBS was based on the changes in Rct values using Fe(CN)63-/4- redox probe.
Integrated electrochemical DNA biosensors for lab-on-a-chip devices
Electrophoresis, 2009
Analytical devices able to perform accurate and fast automatic DNA detection or sequencing procedures have many potential benefits in the biomedical and environmental fields. The conversion of biological or biochemical responses into quantifiable optical, mechanical or electronic signals is achieved by means of biosensors. Most of these transducing elements can be miniaturized and incorporated into lab-on-a-chip devices, also known as Micro Total Analysis Systems. The use of multiple DNA biosensors integrated in these miniaturized laboratories, which perform several analytical operations at the microscale, has many cost and efficiency advantages. Tiny amounts of reagents and samples are needed and highly sensitive, fast and parallel assays can be done at low cost. A particular type of DNA biosensors are the ones used based on electrochemical principles. These sensors offer several advantages over the popular fluorescence-based detection schemes. The resulting signal is electrical and can be processed by conventional electronics in a very cheap and fast manner. Furthermore, the integration and miniaturization of electrochemical transducers in a microsystem makes easier its fabrication in front of the most common currently used detection method. In this review, different electrochemical DNA biosensors integrated in analytical microfluidic devices are discussed and some early stage commercial products based on this strategy are presented.
Analytical Chemistry, 2011
b S Supporting Information E lectrochemical DNA biosensors (E-DNA) appear to be a promising alternative to optical sensors for the specific detection of oligonucleotide sequences. 1À3 These devices are composed of a redox-reporter-modified DNA probe immobilized on a gold electrode. Hybridization-linked changes in the flexibility of this probe (due to specific conformational changes 1,4,5 or an increase in the amount of double-helix 6 ) alter the rate with which electrons are transferred from the redox reporter, leading to a readily detectable change in Faradaic current upon voltammetric interrogation. 7,8 Because E-DNA sensors are driven by electrochemistry, rather than optical detection methods, they can be integrated into microfluidic devices, powered by inexpensive, hand-held electronics, and easily multiplexed. 9À11 Moreover, because their signaling is predicated on a binding-induced change in the physical properties of the probe DNA, rather than to adsorption of analytes to the sensor surface, E-DNA sensors are relatively insensitive to the nonspecific adsorption of interferants and are selective enough to deploy directly in complex clinical and environmental samples, such as blood or soil extracts. 12,13 E-DNA sensors thus appear well suited for point of care medical diagnostics, as well as portable analysis systems for forensics and food quality control. Although E-DNA sensors have a wide variety of positive attributes, many of the diverse E-DNA probe architectures described to date operate in a signal-off fashion, meaning that the measured current decreases as the concentration of analyte DNA increases. 14 For example, first generation E-DNA sensors employ a stem-loop architecture 1,14 such that, when a complementary target oligonucleotide is introduced, hybridization causes the stem to open. This moves the redox reporter further from the electrode surface, reducing electron transfer. This signal-off mechanism significantly limits the gain of the sensor: the maximum possible ABSTRACT: Electrochemical DNA (E-DNA) sensors, which are rapid, reagentless, and readily integrated into microelectronics and microfluidics, appear to be a promising alternative to optical methods for the detection of specific nucleic acid sequences. Keeping with this, a large number of distinct E-DNA architectures have been reported to date. Most, however, suffer from one or more drawbacks, including low signal gain (the relative signal change in the presence of complementary target), signal-off behavior (target binding reduces the signaling current, leading to poor gain and raising the possibility that sensor fouling or degradation can lead to false positives), or instability (degradation of the sensor during regeneration or storage). To remedy these problems, we report here the development of a signal-on E-DNA architecture that achieves both high signal gain and good stability. This new sensor employs a commercially synthesized, asymmetric hairpin DNA as its recognition and signaling probe, the shorter arm of which is labeled with a redox reporting methylene blue at its free end. Unlike all prior E-DNA architectures, in which the recognition probe is attached via a terminal functional group to its underlying electrode, the probe employed here is affixed using a thiol group located internally, in the turn region of the hairpin. Hybridization of a target DNA to the longer arm of the hairpin displaces the shorter arm, allowing the reporter to approach the electrode surface and transfer electrons. The resulting device achieves signal increases of ∼800% at saturating target, a detection limit of just 50 pM, and ready discrimination between perfectly matched sequences and those with single nucleotide polymorphisms. Moreover, because the hairpin probe is a single, fully covalent strand of DNA, it is robust to the high stringency washes necessary to remove the target, and thus, these devices are fully reusable.
Innovative configurations of electrochemical DNA biosensors (A Review)
Abstract: In the field of electrochemical biosensing, transition metal complexes achieved a significant importance as hybridization indicators or electroactive markers of DNA. Their incorporation in electro-chemical DNA biosensors enables to offer a promising perspective in understanding of the biological activity of some chemical compounds. In this context, the development of innovative configurations of electrochemical DNA biosensors applied to life sciences during the last years were reviewed in the present article. In the first part, a brief introduction of nanomaterial based electrochemical DNA biosensors is given. In the second part, the complexes of transition metals with biological interest and their applications in electrochemical DNA biosensors are being described.