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What is the principle of nano silver antibacterial? What is the antibacterial effect?

Silver ions are positively charged cations formed by metal silver losing more than one electron, such as Ag1+, Ag2+, Ag3+, etc. In the form of an aqueous solution, silver ions have an oxidizing effect and are often used for sterilization and disinfection. Silver ion antibacterial agent is a kind of high effect and safety among many textile antibacterial agents, so how to distinguish between nanosilver ion and electrolytic silver ion antibacterial agent? What is the difference between the two antibacterial? This article is for you one by one.

1. The popularization of basic concepts and common sense
1. Molecules, atoms, electrons, ions Molecules are the smallest particles that exist independently and maintain the chemical properties of matter. Atoms are the smallest particles that makeup matter. An atom consists of a nucleus and electrons surrounding the nucleus. The overall polarity of the atom is neutral. If the number of protons and electrons of an atom are not equal, it becomes an ion. If the number of electrons is greater than the number of protons, the ion polarity is negative, otherwise, the ion polarity is positive. Ions with negative polarity are called anions, and ions with positive polarity are called cations. In the chemical reaction, the metal element atom loses the outermost electron, and the non-metal atom gains the electron so that the atoms participating in the reaction are charged. Charged atoms are called ions, positively charged atoms are called cations, and negatively charged atoms are called anions.
2. The volume of nanometers and ions. A nanometer is a unit of length, which is one-billionth of a meter (meter→cm→mm→micrometer→nanometer), which is about one ten-thousandth of the thickness of a hair. 1 micron = 1000 nanometers, that is, units of 1 to 999 nanometers are called nanometers. The size of an atom is one ten-millionth of a millimeter (mm). One ten-thousandth of a micrometer (μm). In this way, we can know that 1 nanometer is about the size of 10 ions (atoms). The manufacturing technology of nano-silver is 4 to 5-nanometer units in Japan. That is, one nano-silver powder particle can hold 40-50 ions (atoms). In general nano-silver manufacturing technology, the size of micro-powder particles is 10-20 nanometers. That is, it can hold 100 to 200 ions (atoms).
3. The size of microorganisms is measured in microns. For example, a standard paramecium-a single-celled freshwater creature-is approximately 2 microns wide. The diameter of cocci is about 0.75-1.25 microns (μm), the length of bacilli is about 2-5 microns (μm), and the length of spiral bacteria is about 100-200 microns (μm). Viruses are much smaller than bacteria and must be seen through an electron microscope. Ions (atoms) are tens or hundreds of thousands of the size of bacteria. Silver ions act as cations, so they are easily adsorbed by anionic bacteria and enter the bacteria's body.
4. Bacteria reproduce by division, and viruses reproduce by self-replication. Bacteria and viruses reproduce extremely fast, increasing exponentially. Generally, it only takes 20 to 30 minutes for a cell to divide. The conditions are suitable, the virus replication cycle is short, and it may multiply millions of times within tens of minutes.
5. Antibacterial, sterilization, disinfection, anti-microbial (anti-microbial): is a general term, including sterilization and antibacterial. Sterilization (microbiocide): refers to the process of killing microbial nutrients and propagules in the system to be treated. Disinfection: Refers to the process of destroying microorganisms in the system to be treated, but the disinfection process is generally ineffective for microbial spores. Disinfection does not need to kill all microorganisms in the system. It only needs to meet the predetermined treatment requirements. Generally, the system needs to be diseased. And the disease-causing microorganisms go out or lose their activity. Bacteriostasis: inhibits the growth and reproduction of microorganisms, inhibits the activity of microorganisms in the system to be treated, reduces their reproductive capacity, or stops the process of reproduction.

2. Silver ion antibacterial agents in inorganic antibacterial agents are generally divided into two categories: inorganic and organic.
Organic antibacterial agents are mainly chemical antibacterial agents, which destroy cell membranes through chemical reactions, have fast sterilization, good effects, low cost, and wide application. But the safety is poor, the effect is not lasting, and resistant bacteria are prone to appear. Inorganic antibacterial agent, safe, long-lasting, high-temperature resistance. No resistant bacteria will appear. Metal ions are a very important part of inorganic antibacterial agents, especially silver antibacterial agents that have been most widely used in recent years. The antibacterial component of the silver-based antibacterial agent is a silver ion. As an antibacterial agent, silver ion has the advantages of safety, broad-spectrum, long-lasting, non-tolerant bacteria, and significant antibacterial effect. It is a very ideal antibacterial agent. The disadvantage is that the silver ion is unstable and the processing cost is high. Silver non-resistant bacteria appear, that is, the bacteria are not resistant to silver ions. This is due to the unique sterilization mechanism of silver ions.
The general antibacterial agent mainly kills the cell membrane by destroying it. As a result, the bacteria that have been hit hard are constantly evolving and adapting to increasingly toxic chemicals. There are even so-called "super bacteria" that are almost "invulnerable" and no medicine can deal with it. And these "super bacteria" used to be some more "tame" bacteria. Just like the alchemy furnace of Taishang Laojun made Sun Wukong into golden eyes, he was also "tempered" into super pathogenic bacteria that can decompose medicines and are very toxic, which can kill people, such as coliform O-157 and resistant grapes. Cocci (MRSA) and so on.
In summary, the mechanism of silver ion's antibacterial (killing) mechanism can be summarized by two universities.
First, the theory of bacterial cell division and reproduction hindered. Silver ions are adsorbed as cations and enter the cell membrane of bacteria, and react with intracellular enzymes, causing protein metabolism disorders, leading to metabolic disorders, and the stop of cell division (proliferation). Bacteria deplete their energy and lose vitality in the process of eliminating foreign components in the body.
The second is the activation of silver ions to produce reactive oxygen species (OH-), which oxidizes and decomposes bacteria and viruses. Silver ions are the most active kind of metal ions. In the presence of light and water (the air contains a certain amount of water), silver ions will be activated to produce active oxygen (OH-). This safety is equivalent to the active oxygen (OH-) of natural ions, and it does have the oxidative decomposition ability several times that of ultraviolet rays and ozone and has the killing and decomposing effect on bacteria and viruses. In recent years, Japan's Sharp, Panasonic, and other home appliances have adopted this sterilization and deodorization technology. Recently, some researchers in Japan confirmed that even in dull water, silver ions will produce active oxygen (OH-). The above two theories of antibacterial (killing) mechanisms are supported by modern scientific tests such as the electron microscope. However, no matter which kind of argument it is, it can fully explain that the silver ion inhibits (kills) bacteria and viruses, making it impossible for bacteria and viruses to appear resistant.

3. The past and present of silver ion antibacterial agent Silver ion is a traditional antibacterial agent that is often introduced. When metallic silver is in the water, or in the air (there is a certain amount of water in the air), a small number of silver ions will be released on the surface of the silver, so it has a certain sterilization effect. From ancient times, people began to use silverware. People found that the milk in the silver food container will not deteriorate, the food will not deteriorate, and the silver earrings will not cause skin infection and inflammation. Monks in Southeast Asia are still using silver bowls for alms. These are all examples of human empirical use of the antibacterial effect of silver. Later researchers were inspired by it and developed various types of silver ion antibacterial products from experience to rational research. People have been able to prepare silver ion solutions in the laboratory for a long time. In 1884, German obstetrician and gynecologist Crede dripped a 1% silver nitrate solution into the newborn's eyes to prevent neonatal conjunctivitis and reduce the blindness rate of infants from 10% to 0.2%. To this day, many countries are still using the Crede prevention method. In the 1920s and 1930s, countries such as Germany, France, and the old Soviet Union used electrolytic silver ions to sterilize tap water. The Japanese army also used electrolytic silver ions to sterilize the drinking water in the occupied areas during the war of aggression against China. However, due to poor manufacturing technology, low silver ion concentration, and high cost, it was difficult to form industrial production. In the future, the sterilization and disinfection from the incoming water can only give way to the new chemical agent-chlorine. After the emergence of chemically synthesized antibacterial agents represented by chlorine, due to their strong bactericidal power, high speed, and low cost, they soon dominated most of the antibacterial market. Except for special antibacterial agents such as silver nitrate eye drops, silver ions have lost the market. More than a decade ago, nanotechnology emerged. Scientists have discovered that the sterilization efficiency of silver has a lot to do with its surface area. By increasing the surface area, the release of silver ions can be increased, and its sterilization ability has a qualitative leap. In other words, a very small amount of silver can be attached to the nano-scale carrier to produce a strong bactericidal effect. As a result, nano-silver powder (or silver-loaded) became fashionable for a while. Some countries even support it as a new industry, competing to develop nanosilver. The industrial production of silver ion antibacterial agents by electrolysis has always been the dream of many researchers. The once-popular electrolytic method of silver ions was ultimately restricted by the technical and historical conditions of the time and was not realized. The reason for the difficulty of industrial production: Silver ion is an extremely active ion, which is very easy to react with other substances and is difficult to preserve. The decomposition, purification, and concentration of high-concentration and high-purity silver ions are even more difficult, and the production environment is demanding. This is the reason why silver ion solutions produced by electrolysis are rarely seen in the market. The low-concentration and unstable silver ion products have no use-value. Logistics storage costs are high, and there is no commercial value. In recent years, in Japan, electrolytic production has finally achieved a technological breakthrough. Finally, it is possible to produce an electrolytic silver ion solution with high purity and stable performance that can be diluted hundreds of times, with a pure ion concentration of hundreds of ml/g or more. It broke the current market situation where there is only a single species of silver ion for nanosilver. Make the popular use of silver ion antibacterial agents possible. The silver ion solution prepared by electrolysis has no carrier of nano-silver and contains simple and pure ingredients without impurities. It can be directly used for the disinfection of human skin and mucous membranes and environmental disinfection. Highly concentrated silver ion solution, colorless, odorless, transparent, easy to compound processing, storage, and transportation. The silver ion obtained by electrolysis is a pure silver ion preparation without any attached carrier. After a certain amount of silver ions are consumed, there are no silver ions, so it is safe. There is no problem with the accumulation of silver ions, and there are no ecological and physical safety concerns caused by the accumulation of nano-silver in the environment or in the body. The silver ion concentration obtained by the electrolysis method is pure silver ion concentration, which can be measured by accurate concentration standard measurement. The pure silver ion diluent with a concentration of 0.5~1.0ppm can kill most bacteria and viruses. The application history of silver ions for more than one hundred years is mainly the application history of silver ions by electrolysis. Authoritative organizations, including the International Health Organization (WHO), have classic discourses on the application of silver ions, and detailed information is available for reference in how much concentration has a bactericidal effect on which pathogens. These data are all based on pure silver ion by electrolysis. In the literature of the International Health Organization (WHO), there is no information about nano-silver ions.

Fourth, the classification and characteristics of silver ion antibacterial agents
1. Pharmaceuticals include powder and solution. Appeared earlier. In the modern pharmacopeia, four silver-containing drugs, including silver nitrate, protein silver, silver silicate, and silver sulfadiazine, are successively included for the treatment of conjunctivitis, gonorrhea, cystitis, dysentery, enteritis, burns, and other diseases. . The representative product is silver nitrate eye drops. The most used is silver nitrate. Medically, 1% silver nitrate is often used for neonatal eye drops to prevent gonococcal infection and for the treatment of conjunctivitis.
2. Electrolytic silver ionic liquid. It appeared early, but it is difficult to industrialize for a long time. High concentration and high purity manufacturing is the latest breakthrough.
3. Nanosilver or loaded silver. powder. There are many kinds of carrier materials available in the manufacturing method, so there are many products on the market. The manufacturing process of nano-silver requires minerals such as zirconium phosphate, apatite, and zeolite as carriers, and the silver content is about 3%. The principle is to increase the unit surface area of ​​silver by processing the silver-containing carrier into nano-sized powder to increase the release of silver ions and increase the sterilization power. The main purpose of nanosilver powder is to process antibacterial fibers. If the nanosilver powder is processed into an aqueous solution, the processing method is to dissolve the powder in water. Therefore, the nanosilver solution is a solution containing the carrier, and the concentration of the nanosilver solution is the silver ion concentration of the mineral carrier. Nanosilver is actually a general term for products with various manufacturing methods, different carriers, and uneven quality effects. Nanometer units can be called nanometers from 1 to 999 nanometers. For every difference of 1-nanometer unit, the difference in surface area will increase geometrically. It is conceivable that the surface area difference between a 1-nanometer unit and the 999-nanometer unit can be huge. The smaller the nanometer unit, the larger the surface area, the more silver ions are released, and the better the sterilization effect. Therefore, the quality and price of the same nano-silver are very different. At present, the nanometer unit of the world's highest level of nano-silver products (Japan Toagosei Co., Ltd.) is 4 nanometers. The general nano-silver product is about 20-30 nanometer units. Good and bad products are uneven, and the price disparity can be imagined. In addition, it is difficult to verify nanometer units, and it is difficult for customers to judge even with the help of sophisticated instruments. This affects the credit of Nano Silver. Therefore, it is also called Zayin (Nano-silver). In the market, some are sold for several thousand yuan per kilogram, and some are only several hundred yuan. The difference is more than ten times, and it is difficult for customers to comply.
The above three types of silver ion antibacterial agents all contain silver ions to achieve their sterilization function. Different types of silver ion antibacterial agents are limited in their use occasions due to their different physical forms, properties, and ingredients. Although silver ion antibacterial agents, represented by silver nitrate, appeared earlier. However, nitric acid is present, so the use is mainly limited to eye drops. In developed countries such as Europe, America, and Japan, it is not allowed to be used for skin and mucous membranes and environmental disinfection. Silver nitrate and other pharmaceutical antibacterial agents are professionally used, and nano-silver and electrolytic silver are widely used, and they are relatively easy to be confused. Nano-silver solution and electrolytic silver ion solutions are the same but different concepts. This is to be pointed out in particular. The bactericidal components contained are silver ions. But the content is different. The electrolytic silver solution contains pure silver ions, while the carrier contained in the nano-silver solution is the main component, and the silver ions are only a small amount. Second, the concentration measurement units used for nanosilver and electrolytic silver are both ml/g (ppm), and the declared concentration in the internationally accepted electrolytic silver solution is the concentration of pure silver ions. The labeled concentration of nanosilver is the concentration containing the nanocarrier. Also, because nano-silver manufacturers have different technologies, even with the same labeled concentration, the actual concentration of silver ions contained is also different, so the sterilization effect is naturally different. From the above, the concentration of electrolytic silver ion solution and nanosilver ion solution is difficult to compare. We can only use the lowest inhibitory concentration as the standard to make a rough analysis and comparison. 250~500ppm of nanosilver solution is equivalent to a pure silver ion concentration of 1ppm. That is, the antibacterial activity of the electrolytic silver ion solution at 1 ppm is approximately equivalent to the antibacterial activity of the nano-silver solution at a concentration of 250 to 500 ppm. Namely: Nanosilver ion solution [MIC] is: 62ppm~250ppm Electrolytic silver ion solution [MIC] is: 0.05ppm~0.5ppm The simple concentration comparison is about 500:1. Form: Electrolytic silver ionic liquid is a colorless, odorless transparent liquid. Nanosilver solution is divided into two types: colorless and transparent liquid and brown solution due to different carriers. The brown solution uses cheap materials such as apatite, and the price is low. The physical form of nanosilver is powder. In the market, Many solutions that use nanosilver powder to replace silver ions are sold. The speed and concentration of silver ion dissolution (dissociation) from the carrier vary depending on the nanosilver powders of various manufacturers, and the process is complicated and the price is high. Therefore, processing the silver ionic liquid from nanosilver is not the advantage of carrying silver. Nanosilver is used in many fields such as antibacterial film, sanitary wipes, disinfection spray, and so on. The electrolytic silver ion product is a liquid. It is a high-purity, colorless, odorless, and non-toxic transparent aqueous solution without carrier particles. Therefore, it can be used for mucosal tissues such as eyes, oral cavity, nostrils, skin, and vagina. As long as silver ions do not react with other elements, do not generate silver compounds, and do not become new substances, the sterilization effect of silver ions always exists. Even if the silver ions enter the nucleus of the bacteria after the bacteria die, they are dissolved again, and they can still be sterilized again and again.