Biochip technology

Rrelevant topics Bio
chip technology
is a comprehensive high-tech emerging in recent years, it is based on micro-electromechanical system technology and biotechnology, life science research in many unsecontural processes (such as sample preparation, biochemical reactions, testing and other steps) integrated and transplanted to a common stamp-sized chip, and these decentralized processes are continuous, miniaturized, in order to achieve a large number of biological information processing requirements for rapid and parallel processing.The concept
biochips was inspired by computer chips. In the narrow sense,
biochips
refer to high-density DNA,
proteins
, cells and other microarray chips, such as cDNA microarrays, oligarchic
nucleotides
microarrays, and protein microarrays, which are buried on solid-phase vectors such as silicon wafers, glass, and plastics. These microarrays are formed by bioactive substances in an orderly manner fixed to solid-phase vectors in the form of dot matrixes. Biochemical reactions are carried out under certain conditions, the results are displayed by chemical fluorescence, enzyme labeling,
electronics
method, and then data are collected by a special biochip scanner or electronic signal detector, and finally analyzed by special computer software. A broad biochip is any micro-solid thin device that can quickly process and analyze biome molecules in parallel.since 1991, when Fodor (S. P. A. Fodor and others have proposed DNA chips so far, the biochip technology represented by DNA chips has been rapidly developed. At present, in addition to DNA chip technology, biochip technology also includes
immune
chip analysis technology, chip nucleic acid amplification technology, cell chip analysis technology and chip-based high-volume drug screening technology. The emergence of these emerging technologies will bring a revolution in life science research, disease diagnosis and treatment, new drug development, national defense, forensics, food hygiene inspection, aerospace and other fields. It is precisely because of the rapid development of biochip technology, the American Association for the Promotion of Science as one of the top ten breakthroughs in science and technology in 1998.sample preparation chip biological samples are often complex mixtures that in most cases require pre-treatment of biological samples, i.e. sample preparation. Taking nucleic acid sample preparation as an example, it includes multi-step work such as cell separation, cell breakage, deproteination, dna extraction, etc. This can be done on the sample preparation chip. At present, the more prominent cell separation methods are
filtration
isolation and dielectic swimming separation, and the chip cell-breaking methods are chip heating cells, high-pressure pulsed cells and chemical cell breakup.filtration separation chipis separated according to the size of the bioparticles. In 1998, a team of researchers at the University of Pennsylvania developed a chip microfiltration method for the separation of human white blood cells. Chip microfleets work according to the size of human white blood cells than red blood cells larger characteristics, so that people's outer blood flow through the microfleet only let the plasma and smaller size of red blood cells and plate plates through, while intercepting the larger size of white blood cells. The processing microfiltration chip is done by carving a filter channel of various shapes on the silicon chip, which is several microns in diameter, and then bonding a glass cover on the silicon chip. Through trial and error and design, the microchip filter has transitioned from the original vertical Z-shaped structure to the horizontal dam structure through the vertical strip comb structure. The advantage of using the horizontal dam structure is that the recovery rate of human white blood cells is high, and the filter is not easily blocked. Another application of microchip filters is that it filters out very small amounts of fetal cells in the outer blood of pregnant women for the next step in prenatal diagnosis.dielectric electrophoresis separation chip dielectric electrophoresis separation principle is that cells in high frequency uneven electric field action to produce polarization, different cells due to dielectric characteristics, conductivity, shape and induction of different even electrodes, so by the role of different mesoelectrogenic power. The advantages of preparing samples by dielectic electrophoresis are that by measuring the speed of cell movement, the dielectic properties of cells can be obtained, and the cells can be manipulated, located and isolated without physical contact.biochemic reaction chipbiochemic reaction chip is designed to microcosm the biochemic experiments carried out in laboratory test tubes to a small chip. At present, the more typical bio-reaction chip includes polymerize chain reaction (polymerize chain reac-tion, PCR) chip, pharmaceutical synthesis chip, etc., of which PCR amplification chip is the typical representative of bio-reaction chip.The background to PCR amplification reactions on the chip is that the sensitivity of the detection instruments currently used in the field of biochips is not high enough, so DNA extracted from blood or living tissue needs to be amplified and copied before it can be labeled or applied. For example, when testing a live anatomy sample of a tumor, an abnormal cancer gene needs to be found in thousands of normal genes, which obviously requires the necessary amplification and replication of the sample DNA to be easy to detect. PCR, as the most commonly used method of DNA amplification in biology, consists of denaturation, extension and atrocification, each of which has a operating temperature of about 95 degrees C, 72 degrees C and 60 degrees C, respectively. This reaction allows extremely small amounts of DNA to be amplified thousands of times to meet the needs of the experiment.In addition to the above method, a simpler method is to attach the Paltir device (a semiconductor device that produces a heating or cooling effect by changing the polarity of the voltage at both ends of the device) directly to the back of the PCR amplification chip, where the temperature of the Paltir device can be amplified by simply controlling the temperature of the Paltir device between three
string
zones.detection chip, thedetection chip mainly includes capillary electrophoresis chip and microarray chip.capillary electrophoresis chipcapillary electrophoresis (CE) is a powerful tool for DNA sequencing, forensics, and PCR product analysis. Capillary electrophoresis isolates DNA fragments faster and more accurately than flat gel electrophoresis because higher voltages can be added to both ends of the capillary tube. The disadvantage of capillary electrophoresis is that only one sample can be analyzed at a time, capillary microarray electrophoresis combines the advantages of two methods of flat gel electrophoresis and capillary electrophoresis, and electrophoresis is carried out in parallel on capillary microarray, which can increase the number of electrophoresis lanes and improve electrophoresis speed, which is a method with great application prospects.on the basis of capillary electrophoresis, in recent years developed a more integrated integrated capillary electrophoresis technology. Integrated capillary electrophoresis technology is in silicon, glass, plastic and other substrates etched capillary grooves, closed with a cover plate, filled in the capillary media, so that the entire process of electrophoresis separation integrated into a few square centimeters of substrate. Integrated capillary electrophoresis chip has the advantages of high efficiency, fastness and low sample dosage, and has been used in immunometrics, DNA analysis and sequencing, amino acid and protein analysis, biological cell research.(A. T. Woolley et al. reported that the microchannel array was photoresisted on the glass substrate using lithogram masking and chemical etching techniques, and then the substrate bonded to another piece of glass to form a capillary array, where small holes were drilled into the upper glass sheet as sample input holes. DNA fragments are fluorescently labeled in the buffer, and the results of capillary electrophoresis are detected using a laser cofocus fluorescence detection system. (E. T. Lagally et al. built a PCR-CE device that integrates PCR reactions with capillary electrophoresis. They microprocessed the heating elements required for the thermal cycle directly into the device at a rate of 10 degrees C per second, with a time of 30 seconds per PCR thermal cycle, and transported samples to the PCR reaction chamber at a capacity of 200 nanals using a 50-nanter micro-valve and hydrophobic outlet. Based on this integrated PCR-CE device, it is possible to amplify and detect individual DNA molecules. addition, Liu Yingjie and others have built an integrated capillary device based on polycarbonate material to analyze DNA samples. They used die-molding to process capillary microchannels, and polycarbonate materials received ultraviolet radiation before bonding to enhance hydrophobility. Experiments show that the device can distinguish between 100 base pairs and 200 base pairs in length. 1500 pieces of dna of the base equivalent. The microarray chip DNA microarray chip is based on the principle of DNA hybridization, first fixed the end of many DNA fragments to the chip, and then let the fluorescently labeled sample nucleic acid through the flow or sample to the chip, after the hybridization reaction cleans the chip, the sample nucleic acid left on the chip can be detected by fluorescence detection method. Since DNA microarray chips do not require micro-processing of the substrate first, automated or chemical synthesis methods can be used to directly apply or synthesize biochemical substances on the substrate. At present, there are 4 typical DNA microarray chip preparation methods: light-guided in-place synthesis, contact point coating, chemical injection, ballast injection in-place synthesis. -in-place synthesis method is to combine photothothresitation technology in the microelectronics industry with photochemical synthesis of DNA. First of all, the four nucleotides protected by photosensitive protection group fixed to the slide, and then according to the design requirements with different masks to mask the slide, light protection group at the lighting decomposition, exposure can be added to the new protected nucleotides, so that the cycle can be prepared with a high density and precision DNA microarray chip. Now people have been able to Synthesis of 400,000 sets of oligonucleotides on 6 cm2 slides. The disadvantage of this approach is that it takes a lot of time and money to prepare the mask, because each base bit of oligonucleotide requires 4 masks and 100 masks for synthesized into a microarray chip with 25 base pairs. contact point coating method first synthesizes the DNA probe and then automatically points the probe to a specified location on the slide via a point contact device. The advantages of point contact method are fast, economical, multi-functional, the disadvantage is that each sample must be synthesized, purified and pre-preserved. chemical injection method is the supply of fixed drops, by way of ballast crystals or other forms of propulsion from the nozzle to spray biological samples to the glass substiter. The sample required for the injection method is DNA that has been synthesized, and the difference between it and the point contact method is that the nozzle does not come into contact with the slide. ballast injection in-place synthesis consists of two main steps: first, the preparation of high-density pits on a 75 mm diameter silicon dioxide substrate, each pit is 100 microns in diameter, 30 microns apart, a total of about 100,000 small pits, hydroxyl hydroxyl hydrophobic hydrophobic treatment in small pits, The resulting pit can be used as a miniature reaction pool for DNA synthesis, and then, according to actual requirements, the nucleotides A, T, G and C are loaded into the four ballast nozzles, and the movement of the microarray DNA chip x-y is controlled by a computer, and four nucleotides are sprayed into suitable pits, thus synthesized into the microarray DNA chip in parallel on the prefabrised substrate. Microflower Technology in Biochips In biological, chemical, material and other scientific experiments, it is often necessary to operate fluids, such as sample DNA preparation, PCR reaction, electrophoresis testing and other operations are carried out in the liquid phase environment. If the sample preparation, biochemical reaction, result detection and other steps are to be integrated into the biochip, then the amount of fluid used in the experiment is reduced from milliliters, micro-upgrades to nanalts or skin upgrades, when the powerful micro-fluid device is essential. Therefore, with the development of biochip technology, microflower technology as a key support technology of biochip has been paid more and more attention. microelectronics, microflow technology does not emphasize reducing the size of the device, it focuses on building microflow channel systems to achieve a variety of complex microflow manipulation functions. Similar to macro-fluid systems, the devices required for micro-fluid systems include pumps, valves, mixers, filters, separators, etc. Although the size of the microchannel is quite large compared to microelectronics, it is already very small for fluids. The fluid flow behavior in the microchannel is fundamentally different from the macro-fluid flow behavior that people see in daily life, so micro-devices such as micropors, micro-valves, micromixers, micro-filters and micro-separators are often very different from the corresponding macro-devices. in order to accurately design the devices required in the microflow system, the fluidity quality of the fluid in the microchannel must first be determined. The flow process in microchannels can now be easily quantified using co-focus
microscope
imaging technology, achieving high resolutions that were previously impossible. The world's first micro-fluid device was developed by A. Manzi of Imperial College. Manz, Ramsay, Oak Ridge National Laboratory, USA Ramsey and other scientists were successfully developed in the early 1990s. The device is made on silicon and glass using conventional flat processing processes (lithothing, corrosion, etc.). Although this method of production is very sophisticated, it is expensive and inflexible to meet the needs of research and development. Recently, Whitesides (G. M. Whitesides et al. proposed a "soft lithage" micro-processing method, i.e. printing and forming microstructages on organic materials, which can easily process prototype devices and specialized devices. In addition, this method can construct a three-dimensional microchannel structure, and can control the molecular structure of the surface of the microflow channel at a higher level. is the most sophisticated microflow technology, using holes less than 100 microns in diameter to produce microdrops. This technology can be used to transport trace
reagents
in microreactive reactions, as well as to distribute trace DNA samples to the surface of the vector to form microarrays (see Chemicalization in DNA chip making).