biological sensor

The biosensor consists of a molecular recognition part (sensitive element) and a conversion part (transducer):

Identifying the target to be detected by the molecular recognition part is the main functional element that can cause a certain physical change or chemical change. The molecular recognition section is the basis for the selective measurement of biosensors.

A physical or chemical transducer (sensor) that converts a biologically active signal to an electrical signal

Various types of biosensors have the following common structures: one or more related bioactive materials (biofilms) and physical or chemical transducers (sensors) capable of converting signals expressed by bioactivity into electrical signals. Together, the reprocessing of biological signals using modern microelectronics and automated instrumentation technologies constitutes a variety of biosensor analysis devices, instruments, and systems that can be used.

Biosensors implement the following three functions:

Feelings: Biomaterials from which plants and animals exert their sensation, including: biological tissues, microorganisms, organelles, enzymes, antibodies, antigens, nucleic acids, and DNA. Achieve mass production of biomaterials or biomaterials and reuse them repeatedly to reduce the difficulty and cost of testing.

Observe: Continuity, regular information that is felt by biological materials is converted into information that people can understand.

Reaction: The information is presented to people through optical, piezoelectric, electrochemical, temperature, electromagnetic, etc., to provide the basis for people's decision-making.

The biosensor has the functions of a receptor and a converter. Instruments that are sensitive to biological substances and convert their concentrations into electrical signals for detection.

The substances in the organism that can selectively identify specific substances include enzymes,

structure

Antibodies, tissues, cells, etc. These molecules recognize the functional substances through the recognition process can be combined with the measured object into a complex, such as the binding of antibodies and antigens, enzyme and matrix binding.

When designing a biosensor, it is an extremely important prerequisite to select an identifying functional substance suitable for the measurement object. Take into account the characteristics of the resulting complex. Selecting the transducer based on the chemical change or physical change caused by the molecular recognition of the sensitive element prepared by the functional substance is another important step in the development of a high-quality biosensor. The amount of light, heat, and chemical substances generated or consumed in a sensitive element will produce a corresponding amount of change. Based on these variations, suitable transducers can be selected.

The information generated by the biochemical reaction process is diversified, and the results of microelectronics and modern sensing technologies have provided rich means for detecting this information.

In 1967, SJ Updick and others produced the first biosensor glucose sensor. The glucose oxidase was contained in a polyacrylamide gel to be cured, and the colloidal membrane was fixed on the tip of the diaphragm oxygen electrode to make a glucose sensor. When using other solidified membranes such as enzymes or microorganisms, other sensors that detect their counterparts can be made. Methods for fixing the sensation membrane include direct chemical binding; macromolecular carrier method; and polymer membrane binding method. Has developed a second generation of biosensors (microorganisms, immune, enzyme immunology and organelle sensors), developed and developed third-generation biosensors, and field-effect biosensors that combine system biotechnology and electronics technology, which opened in the 1990s Flow control technology and microfluidic chip integration of biosensors provide new technology prospects for drug screening and gene diagnosis. Because the enzyme membrane, mitochondrial electron transport system particle membrane, microbial membrane, antigen membrane, and antibody membrane have selective recognition functions for the biological structure of the biological material, only a specific reaction plays a catalytic activating role, and therefore the biosensor has a very high selectivity. The disadvantage is that the biocured film is not stable. Biosensors involve biological substances and are mainly used for clinical diagnostic tests, monitoring during treatment, fermentation industry, food industry, environment and robotics.

Biosensors are an interdisciplinary subject that combines biologically active materials (enzymes, proteins, DNA, antibodies, antigens, biofilms, etc.) and physico-chemical transducers. It is an advanced detection method that is essential for the development of biotechnology. And monitoring methods are also fast and micro-analytical methods for the molecular level of matter. In the development of knowledge economy in the 21st century, biosensor technology will be a new growth point between information and biotechnology, clinical diagnosis, industrial control, food and drug analysis (including biopharmaceutical research and development) in the national economy. There is a wide range of applications for research in environmental protection, biotechnology, and biochips. [1]

The sensor is a special device that can acquire and process information. For example, the sensory organ of the human body is a perfect sensor system that senses physical information such as light, sound, temperature, and pressure outside the nose through the eyes, ears, and the skin. The tongue senses chemical odors such as smell and taste. The biosensor is a special type of sensor that uses bioactive units (such as enzymes, antibodies, nucleic acids, cells, etc.) as biosensing units and has a highly selective detector for the target analytes.

(1) Immobilized bioactive substances are used as catalysts, and valuable reagents can be used repeatedly, which overcomes the disadvantages of high enzymatic assay reagent costs and complicated and complicated chemical analysis.

(2) Strong in specificity, responding only to specific substrates, and not affected by color or turbidity.

(3) The analysis speed is fast, and results can be obtained in one minute.

(4) High accuracy, the general relative error can reach 1%

(5) The operating system is relatively simple and easy to implement automatic analysis

(6) The cost is low. In continuous use, only a few cents of RMB are required for each measurement.

(7) Some biosensors can reliably indicate oxygen supply status and by-products in a microbial culture system. In the production control, many complex physical and chemical sensors can be obtained to obtain information. At the same time, they also indicate the direction of increasing product yield.

Sensors with immobilized biological components or organisms as sensors are called biosensors. Biosensors do not specifically refer to sensors used in the field of biotechnology. Its applications also include environmental monitoring, health care and food inspection. Biosensors mainly have the following three classification naming methods: [2]

1. According to biosensors, molecular recognition elements, ie, sensitive elements, can be classified into five categories: enzyme sensors, microbial sensors, organ sensors, tis-ssensors, and immunosensors. Obviously, the sensitive materials used are, in order, enzymes, micro-organisms, organelles, animal and plant tissues, antigens and antibodies.

2. According to a biosensor transducer or a signal converter, a bioelectric sensor, a semiconductor biosensor, an optical biosensor, a calorimetric biosensor, and a piezoelectric biosensor are classified. Etc. The transducers are electrochemical electrodes, semiconductors, photoelectric converters, thermistors, piezoelectric crystals, etc. in this order.

3. The interaction between the measured target and the molecular recognition element is classified as bioaffinity biosensor, metabolized or catalytic biosensor.

The actual interaction between the three classification methods is used.

The biosensor is a high-tech infiltrated by many disciplines such as biology, chemistry, physics, medicine, and electronics. Due to its excellent selectivity, high sensitivity, fast analysis speed, low cost, continuous on-line monitoring in complex systems, especially its highly automated, miniaturized and integrated features, it has been acquired in recent decades. Vigorous and rapid development.

It has broad application prospects in various sectors of the national economy such as food, pharmaceutical, chemical, clinical inspection, biomedicine, and environmental monitoring. In particular, the integration of new disciplines and technologies such as molecular biology and microelectronics, optoelectronics, microfabrication and nanotechnology is changing the face of traditional medicine and environmental sciences. The research and development of biosensors has become a new hot spot in the development of science and technology in the world, forming an important part of the emerging high-tech industry in the 21st century, and has important strategic significance.

The application of biosensors in food analysis includes the determination of food ingredients, food additives, harmful toxins, and food freshness.

(1) Analysis of food ingredients

In the food industry, glucose content is an important indicator of fruit maturity and shelf life. The enzyme electrode biosensor has been developed to analyze glucose in white wine, apple juice, jam and honey. Other sugars, such as sugar, maltose in beer and wort, also have mature measuring sensors.

Niculescu et al. developed an amperometric biosensor that can be used to detect ethanol content in beverages. This biosensor buries a polyprotein alcohol dehydrogenase in polyethylene. The ratio of enzyme and polymer can affect the performance of the biosensor. In the current experiment, the biosensor has a limit of 1 nmol/L for ethanol.

(2) Analysis of Food Additives

Sulfite is commonly used as a bleaching agent and preservative in the food industry. The sulfite current electrode made of sulphite oxidase as a sensitive material can be used to determine the content of sulfite in foods. The linear range is 0~ 6 of negative fourth-order mol/L. Another example is sweeteners in foods such as beverages, puddings, and vinegar. Guibault et al. use an aspartase enzyme-coupled ammonia electrode and has a linear range of 2×10 negative quintuple to 1×10 negative cubic mol/L. In addition, the use of biosensors for the determination of pigments and emulsifiers has also been reported.

(3) Analysis of pesticide residues

People pay more and more attention to the problem of pesticide residues in foods, and governments in various countries are constantly strengthening the inspection of pesticide residues in foods.

Yamazaki et al. invented an amperometric biosensor using an artificial enzyme for the determination of organophosphorus insecticides. Using an organophosphorus insecticide hydrolase, the limit of determination of p-nitrophenol and diethylphenol was negative 7th. Mol, determined at 40°C for 4 min. Albareda et al. immobilized acetylcholinesterase on the surface of a copper carbon paste electrode using a glutaraldehyde cross-linking method to prepare a negative tens of mol/L paraoxon and a negative value of 10 at a detectable concentration of 10. The tenth-mol/L carbofuran biosensor can be used to directly detect the residues of two pesticides in tap water and juice samples.

(4) Examination of microorganisms and toxins

The presence of pathogenic microorganisms in foods will cause great harm to consumers' health. Toxins in foods are not only of many types but also have high toxicity. Most of them have carcinogenic, teratogenic and mutagenic effects. Therefore, they strengthen the pathogenicity of foods. The detection of microorganisms and toxins is crucial.

Beef is easily infected by E. coli 0157.H7. Therefore, a rapid and sensitive method is needed to detect and protect bacteria such as E. coli 0157.H7. Optical fiber biosensors developed by Kramerr et al. can detect pathogens in food within minutes (eg, E. coli 0157.H7.), whereas traditional methods take several days. This biosensor takes only 1 day from detection of the pathogen to regaining the pathogen from the sample and allowing it to grow independently on the medium, compared to 4 days for the traditional method.

There is also a fast and sensitive immune biosensor that can be used to measure the residue of dihydroavermectin in milk. It is based on the cytoplasmic genome reaction and transmits signals through the optical system. The detection limit that has been reached is 16.2 ng/mL. One can detect 20 milk samples a day.

(5) Detection of freshness of food

The detection of the freshness of foods, especially fish and meat, in the food industry is a major indicator for evaluating the quality of foods. Volpe et al. used astragaloside oxidase as a biosensing material combined with a hydrogen peroxide electrode to determine the inosine monophosphate (IMP), inosine (HXR), and hypoxanthine (HX) produced during fish degradation. The concentration, in order to evaluate the freshness of the fish, has a linear range of 5x10 minus 10th power to 2x10 minus 4th power mol/L.

The problem of environmental pollution has become increasingly serious, and people are eager to have an instrument capable of continuous, rapid, and on-line monitoring of pollutants. Biosensors meet people's requirements. A considerable number of biosensors have been used in environmental monitoring.

(1) Water environment monitoring

Biochemical oxygen demand (BOD) is a widely used comprehensive indicator of the extent of organic pollution. Biochemical oxygen demand is also one of the most commonly used and most important indicators in the monitoring of water bodies and the control of sewage treatment plants. The conventional BOD measurement requires a 5d incubation period, and the operation is complex, and the repeatability is poor, time-consuming and labor-intensive, and the interference is large, and it is not suitable for on-site monitoring. Siya Wakin et al. made a microbial BOD sensor using Trichosporoncutaneum and Bacillus licheniformis. The BOD biosensor can accurately measure glucose and glutamate concentrations simultaneously. The measurement range is 0.5 to 40 mg/L and the sensitivity is 5.84 nA/mgL. The biosensor has good stability. In 58 experiments, the standard deviation is only 0.0362. The required reaction time is 5 to 10 min.

Nitrate ion is one of the major water pollutants. If added to food, it is extremely harmful to human health. Zatsll et al. proposed a method for the detection of nitrate ions using a ensemble function field effect tube device. The detection limit of nitrate ion is 7x10 minus 5th power mol, the response time is less than 50s, and the system operating time is about 85s.

In addition, Han et al. invented a novel microbial sensor that can be used to determine trichloroethylene. The sensor immobilized Pseudomonas JI104 on a polytetrafluoroethylene membrane (diameter: 25 mm, pore size: 0.45 μm). The film was then fixed on a chloride ion electrode. The chloride ion electrode with AgCl/Ag2S film (7024L, DKK, Japan) and the Ag/AgCI reference electrode were connected to the ion meter (IOL-50, DKK, Japan), and the change of the recording voltage was compared with the standard curve. The concentration of trichloroethylene. The sensor has a linear concentration range of 0.1 to 4 mg/L and is suitable for the detection of industrial wastewater. Under optimal conditions, the response time is less than 10 minutes. [3]

(2) Atmospheric environment monitoring

Sulfur dioxide (S02) is the main cause of the formation of acid rain mist, and the traditional detection method is very complicated. Martyr et al. immobilized subcellular lipids (liver microsomes containing sulphite oxidase) on cellulose acetate membranes and an oxygen electrode to make amperometric biosensors to detect the acid rain rain sample solution formed by S02. lOmin can get stable test results.

NOx is not only one of the causes of the acid rain mist, but also the culprit of photochemical smog. Charles et al. used a porous membrane to fix

A microbiological sensor consisting of a nitrifying bacteria and an oxygen electrode was used to determine the nitrite content in the sample, thereby deducing the concentration of NOx in the air. Its detection limit is 0.01xl0 minus 6 power mo1/L.

Among various biosensors, the microbiological sensor has the characteristics of low cost, simple equipment, being free from the degree of turbidity of the fermentation liquid, and possibly eliminating the interference of interfering substances in the fermentation process. Therefore, microbial sensors are widely used as an effective measurement tool in the fermentation industry.

(1) Determination of raw materials and metabolites

Microbial sensors can be used to measure raw materials (such as molasses, acetic acid, etc.) and metabolites (such as cephalosporins, glutamic acid, formic acid, alcohols, lactic acid, etc.) in the fermentation industry. The measuring device is basically composed of a suitable microbial electrode and an oxygen electrode. The principle is to utilize the assimilation of microorganisms to consume oxygen, and the amount of oxygen reduction is measured by measuring the variation of the current of the oxygen electrode so as to achieve the purpose of measuring the concentration of the substrate. .

In 2002, Tkac et al. used a glucose oxidase cell biosensor with ferricyanide as a medium to measure the ethanol content in the fermentation industry. The measurement was completed within 13 s. The measurement sensitivity was 3.5 nA/mM. The microbiological sensor has a detection limit of 0.85 nM, a measurement range of 2 to 270 nM, and good stability. In the continuous 8.5 h test, there was no decrease in sensitivity.

(2) Determination of the number of microbial cells

The determination of the cell number in the fermentation broth is important. The number of cells (cell concentration) is the number of cells in the unit broth. Under normal circumstances, it is necessary to take a certain sample of fermentation broth and determine it by microscopic counting. This measurement method is time-consuming and not suitable for continuous measurement. There is an urgent need for a simple and continuous method of direct measurement of cell number in fermentation control. It was found that on the surface of the anode (Pt), the bacteria can be directly oxidized and generate electricity. This electrochemical system can be applied to the determination of cell number. The measurement results are similar to those measured by conventional cell counting methods. The use of this electrochemical cell number sensor allows continuous and on-line determination of cell concentration.

Biosensors in the medical field are playing an increasingly larger role. Biosensing technology not only provides a quick and easy new method for basic medical research and clinical diagnosis, but also has wide application prospects in military medicine because of its uniqueness, sensitivity, and quick response.

(1) Clinical Medicine

In clinical medicine, enzyme electrode is the earliest and most widely used sensor. It has been successfully applied to the detection of blood glucose, lactic acid, vitamin C, uric acid, urea, glutamic acid, transaminase and other substances. The principle is: using immobilization technology to enclose the enzyme on the bio-sensing membrane. If the sample contains the corresponding enzyme substrate, it can react to produce an acceptable information substance, indicating that the response of the electrode can be converted into the change of the electrical signal. Based on this change, it is possible to determine the presence and quantity of a substance. Microbial sensors can be made by using microorganisms with different biological characteristics instead of enzymes. Microbial sensors used in clinical applications include glucose, acetic acid, and cholesterol sensors. If you choose a suitable tissue containing a certain enzyme, instead of the corresponding enzyme made of the sensor is called a bio-electrode sensor. For example, sensors made from pig kidney, rabbit liver, beef liver, beet, pumpkin, and cucumber leaves can be used to detect glutamine, guanine, hydrogen peroxide, tyrosine, vitamin C, and cystine, respectively.

DNA sensor is one of the most widely reported biosensors currently. It is the biggest advantage of DNA sensors for clinical disease diagnosis. It can help doctors understand the occurrence and development of diseases from the levels of DNA, RNA, protein and their interactions. Helps in the timely diagnosis and treatment of the disease. In addition, drug testing is a major highlight of DNA sensors. Brabec et al. used DNA sensors to study the mechanism of action of commonly used platinum anticancer drugs and measured the concentration of such drugs in the blood.

(2) Military Medicine

In military medicine, timely and rapid detection of biological toxins is an effective measure to prevent biological weapons. Biosensors have been used to monitor a wide variety of bacteria, viruses, and their toxins, such as Bacillus anthracis, Yersinia pestis, Ebola hemorrhagic fever virus, and botulinum toxoids.

In 2000, the U.S. military reported that it has developed an immunosensor that can detect Staphylococcal enterotoxin B, ricin, Tula and Clostridium botulinum. The detection time was 3 to 10 min and the sensitivity was 10,5 Omg/L, 5x10 5th power, and 5x10 4th power cfu/ml. Song et al. made a biosensor for detecting cholera virus. The biosensor can detect cholera toxin less than 1xlO in 5min mol/L within 30min, and has high sensitivity and selectivity, and the operation is simple. This method can be used for the detection of protein toxins and pathogens with multiple signal recognition sites.

In addition, in forensics, biosensors can be used for DNA identification and parent-child certification.

There are many potential applications for various types of sensors. The demand for biosensors in the research and commercial fields comes mainly from the identification of specific target molecules, the practicality of biometric components, and disposable detection systems that are superior to laboratory techniques in some cases. Here are some examples:

Applied to detect glucose concentration

Researchers at institutions such as Purdue University in the United States have created new types of biosensors that can perform non-invasive diabetes tests to detect extremely low glucose concentrations in human saliva and tears. This technique does not require tedious production steps, which can reduce the manufacturing cost of the sensor and may help eliminate or reduce the chance of using acupuncture for diabetes testing.

Overview

With the development of bioscience, information science and material science development, biosensor technology has developed rapidly. However, at present,

chip

The widespread application of biosensors still faces some difficulties. In the future, biosensor research will focus on selecting biosensing elements with high activity and selectivity; improving the service life of signal detectors; and improving signal converters. Lifetime; biological response stability and miniaturization, portable and other issues of biosensors. It can be foreseen that future biosensors will have the following features.

Diversification of functions

Future biosensors will further involve various fields of healthcare, disease diagnosis, food testing, environmental monitoring, and fermentation industries. One of the important contents of biosensor research is to study biosensors that can replace the sensory organs such as biological vision, sense of smell, taste, hearing, and touch. This is a bionic sensor, also called a biosensor modeled on a biological system.

miniaturization

With the advancement of microfabrication technology and nanotechnology, biosensors will continue to be miniaturized, and the emergence of various portable biosensors makes it possible for people to diagnose diseases at home and it becomes possible to directly detect foods in the market.

Intelligent integration

The future biosensors must be tightly integrated with the computer to automatically collect data and process data, provide scientific and more accurate results, realize sampling, sample injection, and results, and form an automated detection system. At the same time, the chip technology will increasingly enter the sensor to realize the integration and integration of the detection system.

Low cost, high sensitivity, high stability and long life

The continuous progress of biosensor technology will inevitably require continuous reduction of product cost and increase of sensitivity, stability and longevity. Improvements in these characteristics will also accelerate the marketization and commercialization of biosensors. In the near future, biosensors will bring tremendous changes to people's lives. It has broad application prospects and will surely shine in the market.

Biosensor utility

It is an organism component (enzymes, antigens, antibodies, hormones, DNA) or the organism itself (cells, organelles, tissues) that can specifically recognize and react with various substances to be measured; the latter mainly includes electrochemical electrodes, Ion-sensitive field-effect transistors (ISFETs), thermistors, photocells, fiber optics, piezoelectric crystals (PZ), etc. function to convert biosensors sensed by sensitive elements into measurable electrical signals.

Biosensors can be divided into enzyme sensors, microbial sensors, tissue sensors, organelle sensors, and immunosensors according to the different molecular recognition elements used; they can be divided into electrochemical biosensors, semiconductor biosensors, and heat sensors, depending on the signal conversion elements. Biosensors, photometric biosensors, acoustic biosensors, etc.; can be divided into potential biosensors, current biosensors, and voltammetric biosensors according to different measurement methods for the output electrical signals. Microbial sensors are an important branch of biosensors. Divies produced the first microbial sensor in 1975, which opened up yet another new area for the development of biosensors.

Without damaging the function of microorganisms, microorganisms can be immobilized on a carrier to make a microbial sensor. Compared with enzyme sensors, microbial sensors have the following features:

(1) Microbial strains are much cheaper than the separation and purification of enzymes, making the resulting sensors easy to popularize;

(2) The activity of the enzymes in the microbial cells in the appropriate environment is not easy to reduce, so the life of the microbial sensors is longer;

(3) Even if the catalytic activity of the enzyme in the microorganism has been lost, it can be regenerated by the proliferation of cells;

(4) For complex continuous reactions that require cofactors, it is easier to use microbes

DNA biosensor

A DNA biosensor is a sensing device that converts the presence of target DNA into detectable electrical signals. It consists of two parts, one is the identification element, the DNA probe, and the other is the transducer. The identification element is mainly used to sense whether the target DNA in the sample is contained in the sample; the transducer converts the signal perceived by the identification element into a signal that can be observed and recorded. Normally, a single-stranded DNA is solidified on a transducer, DNA is hybridized, another DNA containing a complementary sequence is recognized, and a stable double-stranded DNA is formed, and the target DNA is processed through conversion of sound, light, and electrical signals. Testing.
The principle of the DNA biosensor is that the double-stranded DNA formed by the hybridization between a single-stranded DNA molecule with a known nucleotide sequence fixed on the surface of the sensor or transducer probe and another complementary ss-DNA molecule will exhibit a certain degree of The physical signal is finally reflected by the transducer. [1]

Skin biosensor

Blood tests may be a common method of tracking certain human health indicators, but a new project led by the US military may change the way it monitors health. The facts show that many of the health indicators flowing in human blood are also present in sweat. [4]

The U.S. military’s project aims to develop skin “biosensors” that can track the flow of substances in the sweat of military personnel to monitor their health status and enhance their performance. The researchers said that this high-tech device looks and feels like an adhesive bandage and can be used to collect real-time measurement data such as heart rate and respiratory rate. [4]

The sensor is a flat electronic chip embedded in bandages designed to record health information that can be downloaded to smart phones and computers. The U.S. military hopes to use this technology to learn how to deploy military personnel most effectively and how to get them to fight at their best. [4]