Electrical DNA detection

Owing to their unique (tunable-electronic) properties, semiconductor (quantum dots) nanocrystals have generated considerable interest for optical DNA detection [12], Recent activity has demonstrated the utility of quantum dot nanoparticles for enhanced electrical DNA detection [33, 34, 50], Willner et al. reported on a photoelectrochemical transduction of DNA sensing events in connection with DNA cross-linked CdS nanoparticle arrays [50], The electrostatic binding of the Ru(NH3)63+ electron acceptor to the dsDNA... 

Electrical conductivity measurements revealed that ionic conductivity of Ag-starch nanocomposites increased as a function of temperature (Fig.l7) which is an indication of a thermally activated conduction mechanism [40]. This behavior is attributed to increase of charge carrier (Ag+ ions) energy with rise in temperature. It is also foimd to increase with increasing concentration of Ag ion precursor (inset of Fig.l7). This potentiality can lead to development of novel biosensors for biotechnological applications such as DNA detection. 

Metal NPs have received tremendous attention in the field of bio-analytical science, in particular the sequence-specific DNA detection [23,24]. This is attributed to their unique properties in the conjugation with biological recognition elements (e.g., DNA oligonucleotide probe) as well as in the signal transduction with optical [22,25], electrical [26], microgravimetric [27] and electrochemical [23,28-30] methods. 

Explain how surface chemistry and coverage affect the success of electrical DNA-hybridization detection schemes. 

Electrochemical devices have proven very useful for sequence-specific biosensing of DNA. Electrochemical detection of DNA hybridization usually involves monitoring a current response under controlled potential conditions. The hybridization event is commonly detected via the increased current signal of a redox indicator (that recognizes the DNA duplex) or from other hybridization-induced changes in electrochemical parameters (e.g., conductivity or capacitance). Modern electrical DNA hybridization biosensors and bioassays offer remarkable sensitivity, compatibility with modern microfabrication technologies, inherent miniaturization, low cost (disposability), minimal power requirements, and independence of sample turbidity or optical pathway. Such devices are thus extremely attractive for obtaining the sequence-specific information in a simpler, faster, and cheaper manner, compared to traditional hybridization assays. 

Oligonucleotides have frequently been used in the construction of nanodevices where they are used as a means of detection, as electrical wires or as a scaffold (see also section on nanodevices in section 3.5). A real-time DNA detection method using ssDNA-modified nanoparticles and micropatterned chemoresponsive diffraction gratings has been reported that allows hybridisa-... 

This technique was also used to monitor the effects of applied electric fields on hybridization and dchybridization not surprisingly, it was found that even small fields can significantly accelerate these processes. Mismatched sequences were particularly susceptible to potential-induced dehybridization, an effect that is potentially useful in discriminating between closely related sequences. As similar electric fields are involved in electrochemical assays, the effects of these fields on the DNA-film structure must be considered in the design and interpretation of DNA detection experiments. 

Figure 5-14. Schematic illustration of DNA detection based on the direct measurement of conductivity using nanoscale electrical leads. The binding of a target sequence to a pair of probe oligonucleotides immobilized on opposing nanoscale electrodes would provide a means to detect DNA sequences using direct conductivity measurements.

Wilson, E. K. (1998). Instant DNA detection. Systems based on electrical signals move from science fiction to reality, Chem. Eng. News, May 25 47. 

The topics discussed in the book include electrochemical detection of DNA hybridization based on latex/gold nanoparticles and nanotubes nanomaterial-based electrochemical DNA detection electrochemical detection of microorganism-based DNA biosensor gold nanoparticle-based electrochemical DNA biosensors electrochemical detection of the aptamer-target interaction nanoparticle-induced catalysis for DNA biosensing basic terms regarding electrochemical DNA (nucleic acids) biosensors screen-printed electrodes for electrochemical DNA detection application of field-effect transistors to label-free electrical DNA biosensor arrays and electrochemical detection of nucleic acids using branched DNA amplifiers. 

Optofluidic Devices for Light Manipulation and Bio-sensing, Fig. 9 Electrical signal detected by translocating the DNA molecules through the nanoptne... 

Oligonucleotides have frequently been used in the eonstruction of nanodevices where they are used as a means of detection, as electrical wires or as a scaffold (see also section on nanodevices in section 3.5). A real-time DNA detection method using ssDNA-modified nanoparticles and micropatterned chemoresponsive diffraction gratings has been reported that allows hybridisation detection of 40-900 femtomoles of surface-bound DNA. ° Carbon nanotubes are widely used for the construction of nanodevices, and DNA-functionalised carbon surfaces and nanotubes have been reported as platforms for electrochemical detection of hybridisation.PNA-modified carbon nanotubes have similarly been used for the detection of hybridisation with DNA. DNA conjugated to carbon and other solid surfaces may additionally be used as molecular wires,and carbon-modified nanotubes have been developed that act as a field-effect transistor. 

Electrical and electrochemical sensors Nanoparticle sandwich assay combined with silver-staining amplification can also be used in electrical DNA sensors. As shown in Figure 28, a DNA capture probe is immobilized in the gap between two electrodes. After sandwich hybridization, the concentration of DNA is measured by a change in electrical current or resistance. This method is quite sensitive and the detection limit is 500 fM. 

DNA biosensor technologies are under intense investigation owing to their great promise for the rapid and low-cost detection of specific DNA sequences. In the following sections, various DNA detection strategies based on electrochemical/electrical techniques that also involve nanomaterials and are with interest for food quality control will be described. 

As mentioned before, several electrochemical biosensors based on direct DNA detection or catalyzed oxidation of DNA G residues require the combination of nanomaterials, DNA-recognition, and electrical detection protocols, allowing them to improve the sensitivity of the devices. Other promising technologies for the analysis of DNA through the use of labels, as described in the following section, have been obtained. 

Ral, S. and Alocilja, E.C. (2010) Electrically active magnetic nanoparticles as novel concentrator and electrochemical redox transducer in Bacillus anthracis DNA detection. Biosens. Bioelectron., 26 (4), 1624-1630. 

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