Electrochemical nano-sensors) and Absorption voltammetry method of surface nanomolecules (Stripping Adsorption Voltammetry)

(Electrochemical nano-sensors) and Absorption voltammetry method   of surface nanomolecules (Stripping Adsorption  Voltammetry) PhD in nano-microelectronics 

Researcher  and author: Dr.   (   Afshin Rashid)

Note: In the construction of electrochemical nano-biosensors, the minimum parts used in a biosensor are: layer recognition molecular and signal transducer that can transmit this signal to a device (device readout). Are connected. 

DNA is usually a good tool as a biosensor because the base-pairing reaction between complementary play sequences is both specific and stable. In this case, the single-stranded probe DNA is immobilized on the detection layer and then reacts with the probe on the surface by pairing the target DNA. The duplication and uniqueness of DNA structures determines their accumulation on the surface. It is on  this surface that the target DNA is captured and a signal is generated. Therefore, immobilizing the nucleic acid of the probe  while maintaining its initial adhesion strength is important for detecting target DNA. But how this diagnostic procedure  is measured depends on the method of the transduction signal, which may be optical, mechanical, or  electrochemical.Optical biosensors based on fluorescent light have features. These types of biosensors are sensitive to molecules per square centimeter. They are made up of rows that are که so that their detection limit is made up of almost  thousands of probes. Because the tools in this field (fluorescence biosensor) are complex and expensive . Gene chips technology is more suitable for laboratory work. Gene chips are appropriate in cases where a lot of work needs  to be done at the same time, such as profiling transcriptional examination or discovery of single nucleotide polymorphism, but clinical diagnoses usually require the collection of this large amount of data. What is important for molecular detection is capability Ensure recognition as well as generality regardless of the order of the game. Therefore, gene chips are not preferred for clinical diagnosis for  reasons such as: they are expensive and the device is complex. Also, for other specific reasons, reading accuracy is  reduced. Another method for measuring the signal optically is the Resonance Plamon Surface method. In this method, the refractive index of a thin metal film substrate is changed, which is due to the adsorption of  analyte and is suitable for detecting the target in cases where the house is a groove groove. Because  in this way we can achieve the target molecule where the detection limit, causing the signal to the hybridization signal  strengthened. This can be done by increasing the amount of material that is on the surface of the film before or after attaching toIncreased target DNA. The resonant Plus ون surface method (SPR) is similar to the expensive and complex fluorescence method, which is why it is so expensive and complex that it is used more for research than for routine diagnostic work  ; One method of measuring the signal by light, which is very clear, is the light reading method, in which single-stranded DNAs  are labeled with gold nanoparticles, which easily change color due to hybridization in the order of the target game . Using silver staining, DNA analysis can be performed with this optical method on very small plates with high sensitivity  . Although the use of gold nanoparticles may be expensive, but this method has the necessary sensitivity and simplicity for clinical diagnoses. 

One way to read or measure a signal is to measure the changes that occur in the immobilized detection layer  that result from binding to the target molecule. In this case, Quartz Microbalance Crystal is mostly used. This device is sensitive and can report the production of a hybrid (mating) at the time of its  creation. One of the limitations of the QMC method is that this method can not be done when the target sample is  in the solution phase, but with advances in this area, ie the creation of new methods of propagation and amplification of the sample  may be removed. Another method of volumetric measurement is the use of  Cantilevers Microf bricated method. In this method by increasing the volume that accompanies the hybridization by The laser beam is detected from the surface of the cantilever. One of the advantages of this method is that it is suitable for developing  linear grooves and that this method can correct non-specific connections. One of the disadvantages of this method is the high cost and complexity of the tools and devices used. Electrochemical methods are very suitable for DNA detection because electrochemical reactions directly generate  electronic signals and therefore do not require expensive converters. In addition, because the order of the immobilized game  can be limited to a single set of electrode substrates, the tracking operation can be performed by a series of inexpensive electrochemical analyzes  . Electrochemical sensors for on-site clinical or environmental testingIs provided. The basis of the sensitivity of electrochemical signals to direct oxidation or catalysis of DNA bases is also based  on the reduction reactions of reporter molecules or enzymes. Various methods are used to measure the  signal electrochemically. The basis of signal measurement in direct DNA electrochemistry is based on the oxidation reaction and DNA reduction in a mercury electrode  , so the amount of oxidized and reduced DNA is proportional to the amount of DNA that is hybridized with the probe. In addition to the old methods of direct DNA reduction, today a method called absorption voltammetry of surface nanomolecules (Stripping Adsorption Voltammetry) is used to select nanomolecules  for direct oxidation of DNA, which is a very sensitive method. In the methodDirect electrochemistry of purine bases is oxidized by materials such as carbon, indiomethin oxide (ITO) gold and polymer -coated electrodes  . Although the direct electrochemical method is a very sensitive method, its application is complex.

Conclusion : 

All molecular-based electrochemical nanosensors rely on a highly proprietary system to detect or track their target molecule. The importance of an electrochemical nano-sensor is to provide a suitable support for connecting the target molecule to the probe and generating an electrical signal that can be measured and read.

Researcher  and author: Dr.   (   Afshin Rashid)

PhD in Nano-Microelectronics