Biosensors, or the Sixth Sense
Employees of the Massachusetts University of Technology ( MIT, Massachusetts Institute of Technology ) proposed a new type of biosensors that are flexible and have a large specific surface area. The basis for the biosensor are microfibers, a conductive polymer is applied to them, and avidin protein molecules are attached to the polymer, in turn. In an article published last fall in the journal Advanced Functional Materials (Impact Factor 8.49), the authors state that such a “three-layer” design makes it possible to catch the smallest concentrations of biotin in a liquid — and 6 times faster than if the analyzer molecules were attached to flat surface. The authors emphasize that a similar biosensor structure can be used to identify other biomolecules — for example, foodborne pathogens.
What is all this for?
A person in the base set 5 kinds of feelings. This is quite enough to hunt down a mammoth or to hear how the branch cracked under the paw of a saber-toothed tiger. Today a city dweller sees a tiger only in a zoo, and a mammoth, if it is found, will be served ready for use, already under sauce. The dangers were crushed - in size, but not to scale. Today, people are frightened by viruses and bacteria, explosives and drugs, toxins and heavy metals. Everyone would like to know how many elements of the periodic table his plate of soup contains or what is in the pockets of that suspicious bearded man. “Chemical vision” is what the modern man lacks today in his ongoing struggle for survival.
Biosensors can just be called the organs of conditional "chemical vision". Unlike traditional methods of chemical analysis, biosensors may not be very accurate (just as our eye is not accurate compared to instrumental measurement), they may not be complete (as we do not hear sound waves in all their ranges). But they must be fast, convenient and cheap, because the basic equipment we have is the same, and everything that is super - we need to buy more for our hard-earned money.
')
How it works?
The principle of action of biosensors is quite simple. Imagine that we need to detect a substance in water or air, and we certainly know that there should not be much of it. That is, this substance is scattered throughout the volume in the form of individual molecules, and each of them has the same structure and spatial geometry. To catch such a tiny object as a molecule, you need a tool no less miniature - that is, most likely, some other molecule. Finding such a molecule is task number one . In addition, if a sensor molecule reacts with a target molecule, the system should give a signal — and a signal that can be easily fixed. To create a system that is as sensitive as possible to the slightest concentrations of the analyte is task two.
The first task, fortunately, has already been solved by nature. Our body (like the body of any other mammal) perfectly knows how to recognize foreign molecules - for example, proteins or sugars. All of them in bulk in this case are called antigens. Their appearance usually means the onset of bacterial or viral infection. Their antibodies, special protein molecules of the immunoglobulin class, are recognized. Even during the development of the embryo, the human body creates about 10 thousand variants of antibodies, slightly differing from each other in the structure of the variable part, which can be compared with a piece of a puzzle. Immunoglobulins circulate continuously in the blood, waiting for such an antigen molecule that would fit their variable part as one element of the puzzle approaches another. Then this antibody gives a signal to the immune system and starts a complex and long cascade of immune reactions, as a result of which many copies of reacted antibody appear in the body.
In more practical applications, this means that a substance of interest can be injected into a mouse or a rabbit, and after a while many antibodies will appear in the blood — specific molecules that will always selectively bind to the molecules of this substance. Well, you can not torment the beast, and all this is done in a test tube - for example, using the technology of monoclonal antibodies .
The second task is already solved by engineers, and there are quite a few possible ways here. One of the obvious ways is to adapt electricity for this purpose. Chemoresistive biosensors respond to changes in resistance that occur when the analyte molecule attaches to the biosensor. Such devices have a number of important advantages: they respond quickly and selectively, are inexpensive, portable and reliable. As a conductor in such sensors it is convenient to use electrically conductive polymers. They are good in their mechanical properties (flexible but durable), they are inexpensive and, in addition, analyzer molecules can be chemically attached to them. Figure 1 shows a schematic diagram of this type of sensors.
The sensitivity of such a material can be enhanced by giving it the largest possible surface, and then more analyzer molecules can fit on it. One of the possible options on this path is to form nanostructures of electrically conductive polymers - “tapes”, “rods”, “threads”. It is modern, but technically rather difficult, and therefore expensive. In the described article, a simpler way is proposed - using the technology of "electro-spinning" (e-spun) to make fibers from a non-conductive material, and then cover it with an electrically conductive polymer. And already to the polymer through the active groups “sew” on the sensor molecules, approximately as shown in Figure 2. Then, when a “sensor-target” connection is formed, the resistance of the conductive polymer changes, and this can be fixed by a specially trained device. PROFIT, as they say in this case on some sites
As a result, the device looks like this:
What can this lead to?
The researchers used the avidin protein molecule as a sensor, and the biotin molecule as a signal. Biotin, between us, is a B vitamin and is quite common: not only is it found in almost all products, our intestinal microflora also feeds the body with this compound. Therefore, to determine the amount of biotin in the food - it is very impractical. But the biotin-avidin model is convenient, since these substances have a very high affinity for each other. Avidin protein was found in a chicken egg, and in his honor it was called: ovo in Latin is an egg. This protein is one of the milestones in protecting the contents of the egg from bacteria. He very selectively binds vitamin biotin, leaving bacteria on a starvation diet. As a result, bacteria lose their ability to grow and multiply.
Therefore, the authors emphasize that their system is only a model on which they worked out the architecture of this type of biosensors. For practical application, avidin will replace other sensor molecules, obviously, the antibodies we already mentioned.
Interestingly, the work was supported by the US Army through the Institute of Military Nanotechnology ( US Army, Institute of Soldier Nanotecnology ). It is possible that very soon, with the help of such or similar constructions, strict American sergeants will control the quality of meals for military personnel. Modern technology - on the march, in the literal meaning of the word.
What is all this for?
"Taste you from my cup"
x / f "Ivan Vasilyevich is changing his profession"
A person in the base set 5 kinds of feelings. This is quite enough to hunt down a mammoth or to hear how the branch cracked under the paw of a saber-toothed tiger. Today a city dweller sees a tiger only in a zoo, and a mammoth, if it is found, will be served ready for use, already under sauce. The dangers were crushed - in size, but not to scale. Today, people are frightened by viruses and bacteria, explosives and drugs, toxins and heavy metals. Everyone would like to know how many elements of the periodic table his plate of soup contains or what is in the pockets of that suspicious bearded man. “Chemical vision” is what the modern man lacks today in his ongoing struggle for survival.
Biosensors can just be called the organs of conditional "chemical vision". Unlike traditional methods of chemical analysis, biosensors may not be very accurate (just as our eye is not accurate compared to instrumental measurement), they may not be complete (as we do not hear sound waves in all their ranges). But they must be fast, convenient and cheap, because the basic equipment we have is the same, and everything that is super - we need to buy more for our hard-earned money.
')
How it works?
“... in 1907, strange sailors appeared in the Libava military port. After waking, prayer and breakfast, they left the barracks, carrying cages with white mice. Only the initiates knew that they were going submariners to their mysterious ships. And they need mice in order to determine the air pollution in the compartments by the behavior of animals. After all, the boat went under water with the supply of oxygen, which was contained in the compartments. But only."
"From the abyss of water: The chronicle of the domestic submarine fleet in the memoirs of submariners", 1990
The principle of action of biosensors is quite simple. Imagine that we need to detect a substance in water or air, and we certainly know that there should not be much of it. That is, this substance is scattered throughout the volume in the form of individual molecules, and each of them has the same structure and spatial geometry. To catch such a tiny object as a molecule, you need a tool no less miniature - that is, most likely, some other molecule. Finding such a molecule is task number one . In addition, if a sensor molecule reacts with a target molecule, the system should give a signal — and a signal that can be easily fixed. To create a system that is as sensitive as possible to the slightest concentrations of the analyte is task two.
The first task, fortunately, has already been solved by nature. Our body (like the body of any other mammal) perfectly knows how to recognize foreign molecules - for example, proteins or sugars. All of them in bulk in this case are called antigens. Their appearance usually means the onset of bacterial or viral infection. Their antibodies, special protein molecules of the immunoglobulin class, are recognized. Even during the development of the embryo, the human body creates about 10 thousand variants of antibodies, slightly differing from each other in the structure of the variable part, which can be compared with a piece of a puzzle. Immunoglobulins circulate continuously in the blood, waiting for such an antigen molecule that would fit their variable part as one element of the puzzle approaches another. Then this antibody gives a signal to the immune system and starts a complex and long cascade of immune reactions, as a result of which many copies of reacted antibody appear in the body.
In more practical applications, this means that a substance of interest can be injected into a mouse or a rabbit, and after a while many antibodies will appear in the blood — specific molecules that will always selectively bind to the molecules of this substance. Well, you can not torment the beast, and all this is done in a test tube - for example, using the technology of monoclonal antibodies .
The second task is already solved by engineers, and there are quite a few possible ways here. One of the obvious ways is to adapt electricity for this purpose. Chemoresistive biosensors respond to changes in resistance that occur when the analyte molecule attaches to the biosensor. Such devices have a number of important advantages: they respond quickly and selectively, are inexpensive, portable and reliable. As a conductor in such sensors it is convenient to use electrically conductive polymers. They are good in their mechanical properties (flexible but durable), they are inexpensive and, in addition, analyzer molecules can be chemically attached to them. Figure 1 shows a schematic diagram of this type of sensors.
The sensitivity of such a material can be enhanced by giving it the largest possible surface, and then more analyzer molecules can fit on it. One of the possible options on this path is to form nanostructures of electrically conductive polymers - “tapes”, “rods”, “threads”. It is modern, but technically rather difficult, and therefore expensive. In the described article, a simpler way is proposed - using the technology of "electro-spinning" (e-spun) to make fibers from a non-conductive material, and then cover it with an electrically conductive polymer. And already to the polymer through the active groups “sew” on the sensor molecules, approximately as shown in Figure 2. Then, when a “sensor-target” connection is formed, the resistance of the conductive polymer changes, and this can be fixed by a specially trained device. PROFIT, as they say in this case on some sites
As a result, the device looks like this:
What can this lead to?
“You're lying, NATO snout, can't a soldier eat two bags of swede!”
Bearded joke.
The researchers used the avidin protein molecule as a sensor, and the biotin molecule as a signal. Biotin, between us, is a B vitamin and is quite common: not only is it found in almost all products, our intestinal microflora also feeds the body with this compound. Therefore, to determine the amount of biotin in the food - it is very impractical. But the biotin-avidin model is convenient, since these substances have a very high affinity for each other. Avidin protein was found in a chicken egg, and in his honor it was called: ovo in Latin is an egg. This protein is one of the milestones in protecting the contents of the egg from bacteria. He very selectively binds vitamin biotin, leaving bacteria on a starvation diet. As a result, bacteria lose their ability to grow and multiply.
Therefore, the authors emphasize that their system is only a model on which they worked out the architecture of this type of biosensors. For practical application, avidin will replace other sensor molecules, obviously, the antibodies we already mentioned.
Interestingly, the work was supported by the US Army through the Institute of Military Nanotechnology ( US Army, Institute of Soldier Nanotecnology ). It is possible that very soon, with the help of such or similar constructions, strict American sergeants will control the quality of meals for military personnel. Modern technology - on the march, in the literal meaning of the word.
Source: https://habr.com/ru/post/136321/
All Articles