Antibacterial agent and antibacterial mechanism

Antibacterial agent and antibacterial mechanism

Antibacterial agent and antibacterial mechanism

Abstract : Antibacterial agents include three major types of inorganic, organic and natural biological antibacterial agents. Inorganic antibacterial agents are mainly developed by photocatalytic and silver-loaded nanocomposite antibacterial materials . Photocatalytic inorganic antibacterial agents rely on photo-excited strong oxidative free radicals for bactericidal action ; metal ion-type antibacterial agents such as silver The agent acts as an antibacterial agent by inactivating the living active substance of the microorganism by bonding with a reactive group such as a sulfhydryl group or replacing a metal ion auxiliary group. Organic antibacterial agents are developed by developing antibacterial agents that are specific to biomolecules ( such as microbial metabolic enzymes, membrane receptors, etc. ) , which act to inhibit or sterilize by acting on cell walls and cell membrane systems, biochemical enzymes, genetic material, etc. effect. Antibacterial agents may be derived from natural biological all organisms, including polysaccharides, polypeptides and glycopeptides polymer species, the future development direction of the main antibacterial materials; they act on the microorganism or the enzyme layer extracellular biologically active substances, microbial Exercise, transmembrane material transport or biochemical reactions. Different antibacterial agents have different antibacterial mechanism and effectiveness for the same pathogen . The same antibacterial agent also has different antibacterial mechanism and inhibition range for different pathogens ; obtaining long-acting and broad-spectrum, both efficient and safe antibacterial Agents , the study of its antibacterial mechanism is very important.

Microorganisms such as harmful bacteria, fungi, and viruses in nature are the main causes of human infection and disease. In the mid-14th century caused a third of Europe's population died of the Black Death and the early 1900s resulting in more than 20 million people worldwide flu deaths; pathogenic E. coli in Japan nationwide "O2157", the British "mad cow disease "," foot and mouth disease, "the United States" anthrax "and the spring and summer of 2003, severe acute respiratory syndrome infection occur (SARS), these diseases have a direct relationship with the pathogenic microorganisms.

With the improvement of living standards , people's requirements for living environment are getting higher and higher. As a result , the production of antibacterial materials has become an emerging industry , and countries around the world have paid more attention to the research of antibacterial agents.

Antibacterial materials are new functional materials with bactericidal and bacteriostatic properties. It works by adding an antibacterial agent. Antibacterial agents can be classified into three types: inorganic, organic and natural biological antibacterial agents. As the antibacterial mechanism of action of different antimicrobial agents on the same kind of different pathogens and effectiveness, as well as with antibacterial agents antibacterial mechanism of action is different for different pathogens and inhibit the scope, therefore, to work out both long-term and broad-spectrum, efficient and safe antimicrobial agent, the study of antibacterial mechanism is very important.

1 inorganic antibacterial agent and its antibacterial mechanism

Inorganic antimicrobial materials are the mid-1980s developed an antimicrobial material having heat resistance, durability, continuity and security advantages, but there are some drawbacks, such as silver-based antibacterial agents, antifungal effect is weak, The disadvantages of large amount of addition, high cost, and easy discoloration. At present, the application research on inorganic antibacterial materials mainly involves metal element antibacterial agents, photocatalytic materials antibacterial agents and nano material antibacterial agents , which are mainly used in textiles, plastics, coatings and ceramics.

1. 1 metal element antibacterial material and its antibacterial mechanism

1. 1. 1   Metal element antibacterial agent

Such antibacterial agents are metals and their compounds , mainly Ag, Cu, Zn and other elements , and their antibacterial properties ( for broad-spectrum antibacterial properties ) are sequentially weakened , wherein the antibacterial property of Ag is about 1000 times that of Zn . These metals or their compounds are combined with inorganic porous carrier minerals such as zeolite, glass, apatite, calcium phosphate and zirconium phosphate to synthesize antibacterial materials by ion exchange or adsorption . Among them, silver antibacterial agents have been widely used. In practical applications , inorganic antibacterial materials use a variety of inorganic metal composite agents. A patent reported a composite antibacterial agent in the form of AB2O4 [1], where A is a divalent metal Mg, Zn, Mn, Ni, Co or Fe ion , B is a trivalent metal Al, Cr, Mn or Fe ion , and O is oxygen. Elements , these antibacterial agents are applied to a porous honeycomb article ( composed of a mixture of clay, silica, etc. ) to impart good antibacterial properties. Regarding the antibacterial property of the polyurethane film [2], the added antibacterial agent is an exchange resin containing Ag + , and the application result indicates that it has a strong antibacterial effect. Silver antibacterial agents are safe to use. Nylon 612, which contains 15% of silver-based antibacterial agent , can be made into a nylon toothbrush wire with strong antibacterial properties [3] . AIM colloidal antibacterial agent developed by the company under the trade name Real Earth silver-containing chelates, in medicine can be safely used as anti-inflammatory drugs without side effects. Another example is the amino acid silver, to form a protein amino acid as a carrier material, an organic high polymer substance having a good compatibility, good hydrophobicity advantages, for human safety and environmental friendliness.

1. 1. 2   Antibacterial mechanism of metal elements

Metal elements act as antibacterial agents in their ionic form. In an environment where the concentration of metal ions is relatively high , the effects of microbial survival are multifaceted. First , there is a high concentration of metal cations outside the microbial membrane , which changes the polarization state inside and outside the normal biofilm , and causes new ion concentration , which hinders or destroys the transportation of small molecules and macromolecules required for cell maintenance. , as Na + / K + transport of sugars and amino acids under the driving action of the pump 2, some of the metal ions can enter the intracellular microorganism. The experimental results show that heavy metals can inactivate most enzymes , but the mechanism of their inactivation is still unclear. Some people think that the positive metal ions complex with the N and O elements of the protein , destroy the spatial conformation of the enzyme protein molecule ; it may also be that heavy metal ions react with the SH group , replace the protons , and even destroy or replace the enzyme activity. metal ions, such as Mg2 +, Fe3 + and Ca2 + and the like. Enzyme is a catalyst for all organisms , which controls the biochemical reaction of microorganisms. Once the enzyme is inactivated , it causes a decrease in catalytic efficiency or loss of performance , so that the biochemical reaction catalyzed by it cannot be performed normally , and the related biochemical reactions are affected , resulting in energy metabolism of microorganisms. And the metabolism of the substance is blocked , so as to achieve the purpose of antibacterial. In addition , metal ions entering the cell can also bind to the nucleic acid , destroying the cell's ability to divide and reproduce. For the antibacterial mechanism of Ag +, mainly there are two views, one that is in direct contact with Ag + bacteria, inhibit and kill bacteria. It has been reported that the bactericidal action of [4,5]Ag + is directly related to the dissolution of Ag + from its ligand. Zhang Wenzheng and others believe that Ag + can strongly bind to the sulfhydryl group of the enzyme protein and inactivate the enzyme is the main reason for antibacterial [6] . Su Yaonan et al mentioned the slow release of metal ions from the ligands [7], but lack of release kinetic experimental data. The authors believe that in this case , it is not possible to rule out that the surface complexed metal ions ( not leaving the matrix ) still have antibacterial activity. Since Ag + N or O action unsaturated coordination ability with the surface of the cell, destroy the cell structure of the surfactant, resulting in cells blocked by physiological change or death activity. Y. Onodera et al. believe that insoluble silver in the boehmite carrier exerts an antibacterial effect superior to that of zeolite silver [8] . Another researcher believes that the antibacterial activity of Ag + is indirectly exerted by generating reactive oxygen around it.

Y. Inoue et al. [9], the short-term exposure , the antibacterial activity of silver zeolite can only be played in the presence of dissolved oxygen , Ag + can activate oxygen into peroxy ions, hydrogen peroxide and hydroxyl radicals. Play a bactericidal effect. The authors believe that the above two views on the antibacterial mechanism of Ag + are justified. 1. 2 Photocatalytic Antibacterial Material and Its Antibacterial Mechanism 1. 2. 1 Titanium oxide antibacterial agent present, photocatalytic antibacterial agents mainly TiO2, ZnO, CdS, WO3, SnO2 and Fe2O3 and N-type semiconducting metal oxide, wherein the higher oxidation activity of TiO2, stability is also strong, toxic to humans. Under the irradiation of light , TiO2 crystal can completely kill the microorganisms in contact with it in a short time , and has the similar advantages as metal ions , with quick effect , durability and no secondary pollution. Silver, copper and zinc ions have a sterilizing effect, as well as inorganic salts and TiO2 were added together to the ceramic glazes prepared ceramic, family, hotels, hospitals or the like over the ceramic with sanitation. On the roof and facades of buildings, often attached bacteria on hospital operating table and walls, if photocatalytic TiO2 coating or brushing the wall in the sun or indoor low-light irradiation, the bacteria can be eliminated quickly.

1. 2. 2   Antibacterial mechanism of titanium oxide

After the band gap of TiO2 3. 2 eV, which absorbs near-ultraviolet light wave of wavelength of less than 387. 5 nm, electrons in the valence band are excited to the conduction band will form a high activity of the negatively charged electrons, while the valence The band also produces a positively charged cavity. Under the action of the electric field , the electron 2 hole pairs are separated and migrate to different positions on the surface of TiO2 . The holes distributed on the surface of TiO2 and the OH- and H2O adsorbed on the surface are oxidized into • OH radicals. Highly active electrons have a strong reducing ability , which can reduce the oxygen on the surface of TiO2 to O-2, and also reduce the metal ions in the water. • The oxidizing ability of OH radicals is the strongest to oxidatively degrade all organic substances , including penetrating cell membranes , destroying membrane structure to decompose bacteria, viruses and cancer cells , and degrading toxins produced by cells ( this is a general antibacterial agent cannot Comparative ) [10] . Since the TiO2 may be applied to all organic matter, therefore, its wider antibacterial spectrum than the spectrum of antimicrobial metal ion.

1. 3 nanometer antibacterial agent and its antibacterial mechanism

1. 3. 1   Nano antibacterial agent

Nanoparticles are metastable intermediates between solids and liquids. Nanomaterials have surface effects, volume effects, quantum size effects and macroscopic quantum tunneling effects . They exhibit peculiar physical and chemical properties and have many new functions and broad application prospects. Nanomaterials having antibacterial function, depending on the mechanism of sterilization, can be divided into two categories: one for the Ag + containing nanomaterials; another TiO2 and other materials containing nanomaterials. The silver-loaded nano antibacterial materials include silver-loaded silicates and silver-loaded phosphates. The silver-loaded silicate-based antibacterial agent is mainly used for low-temperature processing of fiber, plastic and other products ; the silver-loaded phosphorus salt-based antibacterial agent is mainly used for high-temperature processing of ceramic products , and the preparation principle is : using nano-carrier material The pore structure , using a specific cation exchange method to exchange Ag + into the micropores of the nanocarrier , and then using the process of low temperature dehydration and high temperature stabilization of Ag + in the micropores , making it a nano-silver antibacterial material [11] . Nano TiO2 is non-toxic , tasteless , non-irritating , heat-stable and heat-resistant , does not burn , and is white in itself. Nano TiO2 also has the following advantages [12]: First, the effect is good , such as the effect of silver antibacterial agent takes about 24 h , while the antibacterial effect of TiO2 only takes 1 h; the second is that TiO2 is a semi-permanent antibacterial antibacterial effect. Agents , unlike other antibacterial agents, will gradually decrease with dissolution ; third, high safety , TiO2 can be used in food additives, and TiO2 has no adverse effects on the skin when it comes into contact with skin. Therefore , ultrafine TiO2 has been widely used as an antibacterial agent in various industries in recent years.

1. 3. 2   Antibacterial mechanism of nano antibacterial materials

The antibacterial mechanism of nano-silver antibacterial materials ( including silver-loaded silicates and silver-loaded phosphates ) is similar to the antibacterial and antibacterial mechanism of inorganic silver , and relies mainly on the strong antibacterial activity of silver. Study on silver antibacterial agent having a nanoscale antimicrobial particular mechanism, have not been reported, but the material does nanoscale silver has better antibacterial effect. Liu Weiliang reported [11] that a glaze containing a micron-loaded tricalcium phosphate-loaded silver antibacterial agent ( average particle size of 1.3 μm ) and a nano-zirconium phosphate-loaded silver antibacterial agent ( average particle size of 97.8 nm) frit (where the mass fraction of the antimicrobial agent were 2%) had antibacterial effect comparative experiment, the results showed that: the minimum inhibitory concentration of nanoscale antimicrobial agent minimum inhibitory concentration of only 1 micron / 4 (test selected strains It is Escherichia coli, Staphylococcus, Candida albicans ) . Due to the nanocrystallization of the carrier , the antibacterial material has a larger surface area and has a stronger adsorption effect on microorganisms , thereby having a better antibacterial effect. Similar to the silver-loaded antibacterial agent , TiO2 also exhibits higher antibacterial activity after nanocrystallization. Wang Dalin found that ultrafine TiO2 can kill S. mulans strain AHT ( serotype ), and also kills hamster genus Streptococcus SH26 , Streptococcus mutans FA21 and Actinomycetes ATCC219246 [13] . Further , the finer the particle size of TiO2 , the better the dispersibility, and the larger the specific surface area , the better the bactericidal effect. However , some cell walls are sensitive to photocatalytic reactions , and some bacteria have a protective effect on this reaction . Ultrafine TiO2 has different bactericidal effects on different bacteria.

2 organic antibacterial materials and their antibacterial mechanism

2. 1 organic antibacterial agent

At present, organic antibacterial agents still dominate the antibacterial series , and are widely used in plastics, coatings, fibers, paper, rubber, resins, wood, building materials, medical treatment and water treatment. The advantage is that the bactericidal power is strong , that is , the effect is good , and the variety is many . The disadvantages are large toxicity , poor heat resistance , easy migration, and possible microbial resistance. In recent years, inorganic antibacterial agents and natural antibacterial agents have received attention , and a large number of products have entered the market , and the research and development of organic antibacterial agents has been almost at a standstill , and market demand has declined. There are more than 500 types of organic antibacterial agents , but only a few dozen are commonly used. There are organic antibacterial agent [14]: an organic metal, such as zinc pentachlorophenol; organic halide, such as sodium pentachlorophenol; alcohols, phenols, ethers, such as ethyl alcohol, p-nitrophenol, 2-methyl ethylene glycol Ether, etc .; aldehydes, ketones, oximes , such as glutaraldehyde, o-hydroxycyclopentenedione, tetrachloro-p-quinone ; acids and salts , such as sorbic acid ; esters , such as dimethyl fumarate ; nitriles , such as chlorothalonil; guanidines such as chlorhexidine pyridine; organic nitro compounds, such as nitrofurazone; organic phosphorus-based and organic arsenic, such as arsine lauryl. In addition , there are heterocyclic antibacterial agents such as furans, azoles, imidazoles, thiazolines, benzofurans, and benzothiazoles. The antibacterial agent according to its use, can be divided into bactericides, preservatives and mildew algaecides. A bactericide is an antibacterial agent that effectively kills microorganisms , mainly quaternary ammonium salts, ethanol, biguanides, etc. , and is commonly used for machine surface and skin sterilization, food processing plants and restaurant sterilization , water treatment, etc .; preservatives are Refers to antibacterial agents that can prevent and slow down the deterioration of organic matter . Commonly used are formaldehyde, organic halogen compounds and organometallics . They are commonly used in household products, water treatment and ship mooring ; anti-mold and anti-algae agents are used to prevent materials and objects from growing. Algae-degrading antibacterial agents , mainly pyridine, imidazole, halogenated alkane and iodide , are commonly used in paints, wallpapers, plastics, films and leather.

2. Antibacterial mechanism of organic antibacterial agents

It is generally believed that the mechanism of action of organic antibacterial agents can be summarized into three aspects : one is acting on the cell wall and the cell membrane system ; the other is acting on biochemical enzymes or other active substances ; the third is acting on genetic material or genetic particle structure. Quaternary ammonium salts can adsorb negatively charged bacteria , causing damage to the cell wall structure and causing leakage of contents. Alcohol to remove bacteria killing mechanism is membrane lipids, cell and protein denaturation, which most commonly ethanol, a concentration of 70% to 75% of the strongest sterilizing, when the concentration is too high to make the cell surface protein Rapid solidification , the sterilization efficiency decreased. The bismuth bactericide is commonly used as chlorhexidine . When the concentration is low, the cell membrane is destroyed , and the cytoplasm content is leaked out ; when the concentration is high, the bacterial protein is solidified. In addition , the quaternary ammonium salt also has the effects of inhibiting bacterial dehydrogenase, oxidase and the like. Preservatives act primarily by inhibiting the energy metabolism of microorganisms. Preservatives have strong antibacterial and antiseptic activity in the following cases : one is α , β 2 unsaturated carbonyl structure with certain spatial freedom in antibacterial agent molecule ; the other is antibacterial active center and microbial life molecule functional domain energy Direct collision contact occurs ; the third is that the antibacterial agent has suitable hydrophilicity and hydrophobicity to act on the surface of the bacteria or infiltrate the specific tissue in the cell ; Fourth, the antibacterial agent is not easily enzymatically degraded , and the inhibition spectrum of the enzyme in the biochemical process is wide [15] ] . The mechanism of action of anti-mildew and anti-algae agents can be summarized as the destruction of 2SH acidification , the metabolism is blocked , and DNA synthesis is blocked [16] . Sodium diacetate is a high-efficiency, broad-spectrum antibacterial and anti-fungal agent , especially for aflatoxin . It penetrates the microbial cell wall and interferes with the formation of various enzyme systems in the cell , which can effectively inhibit more than ten kinds. The growth and spread of mycotoxins and various bacteria. Pyridine salts have the function of utilizing the electrostatic interaction between their pyridinium functional groups and bacteria ( ie, ecological capture ) [16] . Benzimidazoles interfere with the formation of mitotic bodies in the mitosis of pathogenic bacteria , thereby affecting the cell division process of pathogenic bacteria. Quinolone infiltrates bacterial cells to inhibit DNA gyrase , an enzyme that maintains the supercoiled structure of DNA [17] . C.Miskolci other studies isophthalic triazine antimicrobial mechanism [18], Table isophthalic triazine and phenothiazine other preferentially bound to the types of molecules xanthine, xanthine, and more easily than in combination with AMP and GMP binding. Therefore , it is rich in G on plasmid DNA . 2C The region has greater binding to the phenothiazine than the A2T- rich region. In terms of antibacterial , this drug plays an extremely important role in these areas. The pyrrole antibacterial agent is derived from the natural product, nicuripulin , which is a non-systemic broad-spectrum antibacterial agent. Its mechanism is through inhibition of phosphorylation of glucose related transferases, and inhibits the growth of the fungal mycelium, eventually leading to the death of bacteria. Because of its unique mechanism of action , it has no interactive antibacterial properties with existing antibacterial agents. Pyrimidine amines have a unique mechanism of action , namely inhibition of pathogen protein secretion , including reduction of degrading enzyme levels. The analysis concluded that these enzymes are involved in the entry of pathogenic bacteria into the host plant and cause necrosis in the host tissue , with no cross-resistance. For aldehydes, bactericidal activity was considered alkylation reaction can be explained, that it was the presence of two aldehyde group is necessary to [19], dialdehyde sterilizing power related to chain length, chain length increased, decreased bactericidal activity, However, the bactericidal mechanism of glutaraldehyde is exceptional [20] and is considered to be the cross-linking effect of proteins. This cross-linking is mainly caused by the reaction of an aldehyde group with an amino group , and other reactive groups such as a mercapto group or an imido group may also participate in crosslinking. Glutaraldehyde first acts on the outer membrane , alters the permeability of the cell , destroys the enzyme system , and inhibits the synthesis of DNA, RNA and protein. Apes , such as the anti-AIDS drug Abacavir, trade name Zia2gen, chemical name IS2 cis 2 ( 2 ' 2 amino 26 ' 2 ( cyclopropylamine ) 29 ' H2嘌呤 29 ' 2 base ) 222 cyclopentene 212 methanol , produced by Glaxo2wellcome Co., Ltd. , UK , was launched in the United States in May 1999 . The drug is a nucleoside reverse transcriptase inhibitors, HIV by inhibiting reverse transcriptase, to cause DNA strand breaks, thereby preventing viral replication.

Halogen-containing antimicrobial action and its nature can be divided into an active halogen atom oxidized and covalently stabilized two categories. When using the former activity will decompose atoms, mainly oxidation sterilization; the latter is a halogenated compound, a halogen atom which only serve Modification. Since most organic antibacterial agents can interfere with gene expression and cell associated enzyme system, so while suppressing harmful microorganisms, other organisms are also toxic to cells. This is the main reason hindering the development of organic antimicrobial materials. It is more difficult to improve the safety of organic bacteria materials and their wastes ( ie, become environmentally friendly ecological materials ) . On the current research and application, while people seeking low toxicity of organic antibacterial agent, should be committed to research efficiency and low toxicity of inorganic antibacterial agents and biodegradable environmentally friendly natural biological antimicrobial agent. Second, the comprehensive advantages of various types of antimicrobial agents, to develop composite antibacterial materials have become a hot research.

3 natural biological antibacterial agents and their antibacterial mechanism

Natural biological antibacterial agents are derived from nature , and are obtained through extraction and purification , and the resources are extremely rich. Natural bio-antibacterial agents are the first antibacterial agents used by people . In ancient Egypt, people could use beeswax as an antibacterial agent to preserve mummies. However , the development of natural antibacterial agents has remained at the level of traditional experience. In recent years , with the strengthening of environmental awareness and the rapid improvement of biotechnology research levels , natural antibacterial agents have received more and more attention. According to the source of natural biological antibacterial agents , they can be divided into plant sources, animal sources and microbial sources [21] .

3. 1 plant source natural antibacterial agent and its antibacterial mechanism

At present , plant-derived antibacterial agents are the most studied natural antibacterial agents. China's traditional herbal medicine has a long history, this type of antibacterial agent resources development has great potential, such as Andrographis, garlic, golden buckwheat, bitter wood, berberine and berberine, Houttuynia and Houttuyfonate, are commonly used antibacterial drug. There are many reports on the research of plant antibacterial agents in foreign countries ( see Table 1) . At present, the development of natural antibacterial agents for plants has just started , and the research on its antibacterial mechanism needs to be further studied.

3. 2 microbial source natural antibacterial agent and its antibacterial mechanism

The microorganism itself can also be used as an antibacterial agent. Its antibacterial mechanism is as follows : First, secrete antibiotics. Y. Ouhdouch et al [39] reported that the non-polyene antibiotics from actinomycetes strain separated in several extraction Morocco, it has a strong inhibitory effect on yeasts, molds and bacteria. GM Thorne the like fermentation product of Streptomyces roseosporus is found for the lipopeptide antibiotic daptomycin, can be suppressed almost all Gram-positive pathogens, without cross-resistance [40];. M within the cells of Bacillus amyloliquefaciens Morita et lysin The relationship between activity and structure of Gram-negative bacteria [41], experiments confirmed that the C2 end and N2 end of this endolysin molecular chain are related to antibacterial activity. H.Tsubery et al. studied the antibacterial activity of deamidated derivatives (PMBN) of polymyxin B (PMB) [42]. Although the antibacterial property of PMBN is weaker than that of PMB , it can penetrate gram. The outer membrane of the negative bacteria neutralizes the toxicity of lipopolysaccharide (L PS) . The second is to participate in the competition of nutrition and living space. By taking the natural biological antibacterial agent of the plant-derived table 1 as an example, Ginkgo biloba [38] seeds of Staphylococcus aureus, Pseudomonas and Escherichia coli have weakened active space, consume oxygen and the like to eliminate certain pathogens in the same living environment. The third is to induce the host to develop disease resistance. Microorganisms can induce host defense responses or directly parasitic to pathogens to inhibit pathogens. The fourth is direct action on pathogens. LL Wilson yeast and Trichoderma, etc. can be found in the parasitic pathogen and secrete a fungal cell wall can destroy the enzyme [43]. Therefore , the research on the antibacterial effect of microorganisms provides an important theoretical basis and practical guidance for the development of new natural polymer antibacterial agents.

3. 3 animal source natural antibacterial agent and its antibacterial mechanism

Animal origin antibacterial agents have amino acids, natural peptides, polymers and sugars, is rich in resources. Chen Yuekai et al studied the antibacterial activity of amino acids and found that cysteine ​​has a strong inhibitory effect on Staphylococcus aureus [44] . Cysteine ​​has a strong antioxidant effect , so it is inferred that its bacteriostatic action is related to antioxidant activity. Natural antibacterial peptide, has become a hot topic of antimicrobial agents. It has long been known that human milk and milk contains antibacterial substances, such as lysozyme, lactoperoxidase. Lysozyme has no side effects on human health , and its mechanism of action is to destroy the β 21 , 4 glycosidic bond in the bacterial cell wall peptidoglycan. KH Yu et al. believe that the antibacterial properties of three species of Lepidoptera (Galleria mellonella, Bombyx mori, Agrius) have become a hot topic. Chitosan is a chitin deacetylated product that can be dissolved in many dilute acids. the smaller the molecular weight of chitosan, degree of deacetylation greater, the greater the solubility of the chitosan having a strong antibacterial activity, which MIC values for Escherichia coli, Bacillus subtilis and Staphylococcus aureus reached (250 to 500) × 10 -. 6 Furthermore, chitosan also inhibit plant pathogens, such as 1% chitosan role complete inhibition of fungus Fusarium (F. solani), and Fusarium strain (F. oxysporum cepae) shell. glycans antibacterial effect, that the following two mechanisms: one is chitosan molecule - NH3 + positive chargeability, adsorbed on the cell surface, a layer of polymer film may be formed on the one hand, to prevent nutrients to the cells Internal transportation ,

On the other hand the negative charge on the cell walls and membranes are unevenly distributed, with the destruction of cell wall synthesis solubility equilibrium, dissolve the cell wall, and thus play a bacteriostatic bactericidal effect; the other is an anionic penetrate into the cells by adsorption cells in vivo The substance that disrupts the normal physiological activities of the cells , thereby killing the bacteria. For Gram-positive and Gram-negative bacteria with different cell wall structures , the mechanism of action of chitosan is different. Gram-positive bacteria have a thick cell wall structure, its main role chitosan cell surface, thereby killing the former mechanism is this

The dominant role of bacteria ; Gram-negative bacteria , thin cell walls , small molecules of chitosan can enter its intracellular role , so the latter mechanism plays a leading role. The results show that, with the de-acetylation and concentration increase the antimicrobial activity of chitosan is enhanced. However , there is no consistent conclusion on the influence of relative molecular mass . The reason is that the relative molecular mass of chitosan is not well controlled in the production process, and the other is because of the different molecular mass of chitosan. It has different effects on different strains. It is generally believed that as the relative molecular mass of chitosan decreases , the inhibition against E. coli is enhanced , while the inhibition against S. aureus is weakened. In addition , some alkaloids can also be used as antibacterial agents , such as YRTorres et al. It has been found that alkaloids extracted from a sponge invertebrate have strong antibacterial effects against Gram-negative and Gram-positive bacteria [47] .

4 conclusion

As an ideal antibacterial agent , it should have immediate, broad-spectrum, long-acting, stable and safe antibacterial effects. However, the conventional antibacterial agents, whether inorganic, organic, biological or natural, do not achieve the desired requirements. Various existing antibacterial agents, have a unique antibacterial mechanism, only to make the characteristics of a comprehensive, in-depth research, comprehensive kinds of antimicrobial agents in the antibacterial mechanism, in order to further improve the effectiveness of antibacterial agents. At present , research on antimicrobial materials is facing major opportunities and challenges in China. An important reason for Japan in 1996, pathogenic E. coli infection incident has caused great attention to research and development of antibacterial materials nationwide in Japan, Japan is currently the leader in this field. In 2003 , China suffered from serious SARS virus infection . In the face of such disasters , researchers of antibacterial materials , from the protection of people's health interests , how to further develop effective antibacterial agents , how to in a wider field the antibacterial agent to be applied, which will be faced by our country in the future in the field of antibacterial materials in two main topics.

This article is taken to the [ China Textile Antibacterial Fabric Network ] Please indicate.

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