Electro-chemical nano-biosensors (basis of work - type of application) Identification in DNA nano-molecules (PhD Nano-Microelectronics) (PhD)
Researcher and author: PhD student Afshin Rashid
Note: All molecular-based electrochemical biosensors depend on a very specific system for detecting or detecting their target molecule. The importance of an electrochemical biosensor is to provide a suitable support for attaching the target molecule to the probe and generating an electrical signal that can be read and measured.
In the building of electrochemical biosensors, at least the parts used in a biosensor include a layer recognition molecular layer and a signaltransducer that can be connected to a device readout of these signals. DNA is usually a good tool as a biosensor because the base pairing reaction between complementary match sequences is both proprietary and stable. In this case, the single-stranded probe DNA is immobilized on the detection layer and then reacted with the probe by surface targeting DNA. The duplication and unity of the DNA structures make it very obvious to accumulate on the surface. On this level is the target DNA and signal occurs. Therefore, the nucleic acid probe is immobilized on While retaining its primary adhesion potential, it is important to identify the target DNA. But how this diagnostic procedure is measured depends on the transduction signal method, which may be optical, mechanical, or electrochemical.
Optical signal size (readout Optical)
Fluorescence-based optical biosensors have features. These types of biosensors are sensitive to molecules per square centimeter. They are made up of rows of 7 that have a detection limit 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 best suited for cases where much work is required, such as profiling transcriptional analysis or single nucleotide discovery polymorphism, but clinical diagnoses usually require the collection of large amounts of data. What is important for molecular detection is the capability Confidence in diagnosis as well as publicity regardless of the order of the game. Therefore, gene chips are not preferred for clinical diagnosis for some reasons, such as: expensive and complex machinery. Also due to other specific reasons, reading accuracy is reduced. Another method for measuring the signal by light 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 the analyte and is suitable for target detection in the case of house-to-house groove grooves. This can be done by increasing the amount of material on the surface of the film before or after bondingTarget DNA increased. Resonance Plus ѧ moon surface (SPR) such as fluorescence expensive and complex this expensive and complex because of that it also has more to do further research used to do routine diagnosis, a method of measuring the signal Patriarch light It is very clear that it is a light reading method in which single-stranded DNA is labeled with gold nanoparticles that are readily transformed by hybridization to the target sequence . Using silver staining, DNA analysis can be performed with this light technique on very small, highly sensitive plates . Although gold nanoparticles may be expensive, this method has the sensitivity and simplicity required for clinical diagnosis.
Volume readout signal measurement
One method of reading or measuring 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, the Quartz Microbalance Crystal is mostly used. The device is sensitive and can report hybrid production at the time it was created. One of the limitations of the QMC method is that it cannot be performed while the target sample is in the soluble phase, but with the advances in this area, the development of new methods of amplification and amplification of the sample may be able to overcome this limitation. Another method of measuring volumes is the use of Cantilevers Microf bricated method. In this way the volume increase associated with hybridization is achieved by The laser beam deviation is detected from the surface of the County. The advantages of this method are its suitability for developing linear grooves and that non-specific joints can be corrected with this method. The disadvantages of this method are the cost and complexity of the tools used.
Electrochemical signal measurement:
Electrochemical methods are very useful for DNA detection because electrochemical reactions directly generate electronic signals and therefore do not require expensive transducers. In addition, since the order of the immobilized match can only be limited to a series of electrode substrates, the act of tracing is performed by a series of inexpensive electrochemical analyzes . Electrochemical sensors are available for on-site clinical or environmental testing . The basis of the sensitivity of electrochemical signals to the direct oxidation or catalysis of DNA bases is also the reactivity of the molecules reporter or enzyme resuscitation. There are various methods used for electrochemical signal measurement .The basis of the signal measurement in direct electrochemical DNA is based on the reaction of DNA redox at a mercury electrode , so the amount of oxidized and reducible DNA is proportional to the amount of DNA hybridized to the probe. In addition to the traditional methods of direct DNA reduction today, a method called Stripping Adsorption Voltammetry is used to select direct DNA oxidation nano molecules which is a very sensitive method. In the direct electrochemical method, the purine bases are oxidized by materials such as carbon, indium oxide (ITO) gold, and polymer- coated electrodes . Although the direct electrochemical method is very sensitive, its application is complex.
Author: Engineer Afshin Rashid
PhD student of Nano-Microelectronics at Islamic Azad University, Science and Research Branch, Tehran