Advances in the study of antimicrobial agents and antibacterial coatings.

0 Introduction:people's living standards continue to improve, people's decorative paint requirements are getting higher and higher. Antibacterial coatings are coatings with antibacterial and antibacterial functions made after processing after a certain process by adding antibacterial agents with antibacterial functions and stable presence in the coating film. When antibacterial coatings are used in public places, they can reduce the number of bacteria in public places, reduce the chance of cross-infection and exposure to infection, and when used in the home environment, they can effectively reduce the density of bacteria on items such as furniture and optimize people's living environment. At present, the research of antibacterial coatings mainly focuses on the matching of antibacterial agents and coatings and environmental safety issues.1 Overview of Antibacterial AgentsCurrently, the antimicrobial agents used in coatings are mainly natural antibacterial agents, inorganic antimicrobials and organic antimicrobial agents three categories. All kinds of antimicrobial agents have their corresponding antibacterial agents, for the same kind of bacteria, different types of antimicrobial agents have different functioning agents.1.1 Natural antimicrobial agentNatural antimicrobial agent is the earliest antibacterial agent used in human beings, mainly from some extracts in plants and animals, such as shell polysaccharides, propolis, fish protein and allicin. At present, the focus of development is ultra-fine shell polysaccharose micro-powder, crustacean and so on. Shell polysaccharides are mainly extracted from the shells of shrimps and crabs, and their molecules contain active groups, which inhibit many bacteria.the advantages of shell polysaccharides and their derivatives include wide antibacteriality, good biological compatible, non-toxic and so on. The added antibacterial agents are considered ideal for coatings. The antibacterial effect of shell polysaccharides is related to its relative molecular mass, deacetylization, solution concentration, pH, solvent type, etc.study shows that because crustaceans are a positively charged active substance, in an acidic solution of pH 6.5, the negative charge on the surface of bacterial cells is enhanced by the interaction of molecules. With the increase of the relative molecular mass of shell polysaccharides, its antibacterial activity against Staphylococcus aureus increased, while E. coli was the opposite. The use of natural antimicrobial agents has a high safety, non-toxic to the human body, no stimulation, but the processing performance of natural antimicrobial agents is very poor, easy to decompose at high temperatures lost effect, by the source, cost, extraction technology and many other conditions, but also because of its diversified principles of action, stability is not enough, so in the paint application has a lot of restrictions, can not be mass production.1.2 Inorganic antimicrobial agentsInorganic antimicrobials are a class of antimicrobial agents made from the bactericidal or antibacterial capacity of metals such as silver, copper, zinc, titanium and their ions. Coatings are widely used inorganic antimicrobial agents are: inorganic silver antibacterial agents, TiO2 series photocatalyst antimicrobial agents, zinc oxide crystal swastactin compound antibacterial agents and other inorganic nano antimicrobial agents.inorderable antimicrobials have the advantages of high safety, good durability, good chemical stability and high antibacterial efficiency. Inorger antimicrobials are still the preferred antimicrobial for coating applications. Compared with natural and organic antibacterial agents, inorganic antimicrobials have great advantages and broad market prospects, and their research and application have been widely concerned.inorgic antimicrobial agents can be divided into metal ion-type antibacterial agents and photo-catalytic antimicrobial agents. Metal ion-type antibacterial agent is copper, silver, zinc and other metals and their ions loaded on a variety of mineral carriers, photo-catalytic antimicrobial agent is the use of N-type semiconductor compounds in ultraviolet light exposure or the presence of oxygen and water to produce strong oxidizing substances to make microorganisms inactive, thus playing a role in bactericidal antibacterial.inorganic antibacterial agents have both antibacterial efficiency and broad spectrum, but also inorganic material stability, durability and heat resistance, make up for the lack of organic antimicrobial agents, has become the mainstream of antimicrobial research coatings. Inorganic antibacterial agents mainly have silver antibacterial agents and oxide-type antibacterial agents two categories.1.2.1 Silver antibacterial agentsilver antibacterial agent also known as silver ion inorger antibacterial agent. Its antibacterial technology is that when positively charged metal ions come into contact with the negatively charged cell membranes of microorganisms, they rely on Coulomb gravity to firmly adhere to each other, metal ions penetrate the cell wall into the cell, with sulfur subgeni, The reaction of carbide and hydroxyl causes the protein to solidify, destroys the activity of the cell synthesis enzyme, the cell dies due to the loss of the ability to divide and multiply, and it can also destroy the microorganism's electronic transmission system, respiratory system, material transfer system, play a role in antibacterial, antibacterial.antibacterial agents are widely used in the antibacterial properties of coatings. Reactive oxygen dioxide silver ions have inhibited and killed effects on Glosin, positive bacteria, mold and yeast. Silver ions in inorganic silver antimicrobial agents can easily be converted into brown silver oxide or catalytically reduced to black monolithic silver, not only reducing their antibacterial properties, but also limiting their application in white or light-colored coatings. In addition, the heavy use of precious metal silver, so that antibacterial coating costs are high, restricting the use of silver antibacterial agents in a wider range. 1.2.2 oxide antimicrobial agent oxide antimicrobial agent is a photocatalytic substance, including nano TiO2 and nano ZnO, etc., they through the absorption and scattering of light to prevent or delay the photodegradation of organic polymer emulsions in the coating, while using photocatalytic effects of strong oxidizing substances to deactive microbial cell tissue. Since nanoparticles themselves are not involved in the reaction, there is no loss, so coatings that add these antimicrobials have a long-lasting antibacterial effect. Photo-catalytic oxide-type antimicrobial agents need to be stimulated by ultraviolet light to have antibacterial properties, and the use of UV light in daily life is less, limiting its wide range of applications.
1.3 Organic antibacterial agents . There are dozens of organic antimicrobial agents commonly used in coatings, mainly glycamine salts, metformin, alcohols, phenols, organic amines, pyridine, isopramines and so on. Organic antibacterial agent is through chemical reactions to destroy the cell membrane, so that protein denaturation, metabolism is blocked, thus playing a role in sterilization, corrosion and mold prevention. Organic antibacterial agent has strong bactericidal power, i.e. good effect, rich in sources, but there are toxicity, poor safety, microbial resistance, poor heat resistance, easy migration and other deficiencies. Current research and use of organic surfactant antibacterial agents are usually nitrogen-containing cation compounds, such as seasonal ammonium salt, nitride salt, mimi salt, isoquine salt and other nitrogen-containing heterocycline salts. although the variety of organic antibacterial agents, the principle of action is different, but whether natural or synthetic organic antibacterial agents, its antibacterial principles can be summarized in the following aspects of the following aspects of the :(1) hinder the synthesis of microorganisms, hinder the growth of microorganisms and the production of substances needed to sustain life. (2) Accelerate the oxidation system of phosphoric acid and destroy the normal function of cells. (3) Reduce or eliminate the activity of various metabolic enzymes in microbial cells, hindering the respiratory action of microorganisms. (4) Inhibit the puffing of spores when they germinate, hinder the synthesis of ICTs, and achieve the purpose of destroying spore germination. This process inhibits the growth and reproduction of mold and is of great significance to the inhibition of spore-producing microorganisms. (5) Destroy the synthesis of microbial cell walls. Organic antibacterial agents are used in antibacterial coatings, often there are toxicity and residual toxicity problems, in order to improve the performance of added antibacterial coatings, reduce their environmental, human and animal stimulation and poison, the development of slow release, high efficiency, low toxicity, high safety of organic antimicrobial agents is the focus of future research and development. characteristics of the three types of antimicrobial agents are compared in Table 1. . 2 The current situation of antibacterial antibacterial coatings are generally divided into added and structural types. Traditional antibacterial coatings are added antibacterial coatings. In the added antibacterial coating, antibacterial agent as a additive dispersed in the coating system, due to the migration of antibacterial agent in the coating film, degradation, color change and other reasons, resulting in antibacterial coating antibacterial properties decay, or even loss of antibacterial properties, so that its application has great limitations. Structural antibacterial coating is to have antibacterial function of the base group through a certain chemical reaction, through the chemical bonds to connect it to the base polymer, so that the polymer resin substation to make antibacterial coating. Since the antibacterial group is connected to the substitlic resin in the form of chemical bonds, the antibacterial properties of the coating are more durable and as long as the service life of the coating, it fundamentally solves the many disadvantages of applying antimicrobial agents in traditional added antibacterial coatings. Therefore, the development of structural antibacterial coatings will become the main direction of the future development of antibacterial coatings.
Xu Ruifen team dispersed the surface-treated nanoTiO2 into the phenyl prolactic emulsion to make antibacterial coatings, its bactericidal rate of Staphylococcus aureus, E. coli, dead grass spores are more than 99%, showing strong sterilization properties. In addition, the antibacterial properties of the coating are not limited by the of the light source, and have long-lasting antibacterial and thorough sterilization. Wang Yan to the paint with calcium phosphate as the carrier of the Ag plus inorderable powder, made with good antibacterial properties of antibacterial coatings.
Yang Chao and others reported a water-based nano-silver/fluorocarbon antibacterial coating, when the nano-silver powder content of 0.03%, the sterilization rate of the coating as high as 94%. Xu Ying applied nanoTiO2 sterilization coating on cement sheets to make a coating, examined its inactivation of E. coli, and found that after 24 h TiO2 content of more than 20.3% sterilization coating can completely kill E. coli. Liu Yongping, etc. deposited A12O3 and SiO2 inorderable protective film on tiO2 surface by sedimentation and drying method, modified the silicon propylene interior wall coating, modified coating on E. coli sterilization rate of more than 99%, and not limited by light source conditions, antibacterial effect is thorough and long-lasting. Yu Hui and other preparation of composite nano-antibacterial powder coatings, its performance, acid resistance and alkalinity are in line with industry standards, and has a good antibacterial effect, to meet the requirements of the paint industry. Chen Liqiong and other nano-silver antibacterial inner wall coating prepared by chemical reduction legal system, is a kind of excellent performance of green environmental protection paint, its addition of nano-silver sol particle size is small, good dispersion, strong antibacterial effect, good stability, the resulting coating has a better antibacterial effect. Deng Yuequan and others put forward zinc antibacterial functional materials - antibacterial coatings integrated preparation technology, to obtain antibacterial properties and basic performance of the functional coatings, to achieve zero emissions of waste, ecological recycling of resource materials. Antibacterial coating products not only their own environmental protection, but also can solve the problem of indoor air quality after decoration is not up to standard, for the hospital environment, can also reduce the risk of cross-infection, play a role in helping to purify the air. Japan's Amuniyou Osaka Cement Co., Ltd. introduced an antibacterial coating that adds 0.01% (mass fraction) of 20 nm and 50 nm of silver particles to the coating to obtain an antibacterial coating when the concentration is 8.4 x 105 cfu/mL E. coli with a concentration of 6.6 After x 105 cfu/mL of Staphylococcus acobacteria was exposed to a 50 nm silver grain coating containing 0.01% (mass fraction), the residual colonies of 5 cfu/mL, i.e. 99.999% E. coli and Staphylococcus acolytic were killed. After exposing the antibacterial coating to 400 h in daylight, there was no significant change in color. Deego Meseguer Yebra, of the Department of Chemical Engineering at the Technical University of Denmark, studied factors that affect the rate at which killers are released. He pointed out that the pores of the coating, the roughness of the coating, the number of cracks in the surface when the coating was painted, the boundary layer part of the coating surface that contacts and interacts with the outside water body, the biofilm layer outside the antibacterial coating, etc. all affect the release rate of antibacterial components in the coating. The greater the porosity of the coating, the coarser the coating, the more cracks in the coating surface, the faster the release rate of antibacterial components. Conversely, the presence of biofilms outside the antibacterial coating slows the release rate of antibacterial components. . 3 Conclusion: With people's health and environmental safety requirements continue to improve, the development of antibacterial functions of coatings has become a hot topic in the paint industry. Internationally recognized ideal antimicrobial agents should have safe non-toxic (low toxicity), durable antibacterial, broad-spectrum antibacterial and non-resistant characteristics, existing natural antimicrobials, inorganic antimicrobials and organic antimicrobials are advantages and disadvantages coexist. In order to further develop new antimicrobial agents, China should increase investment in the antibacterial agent antibacterial agent and test conditions, a comprehensive and in-depth study.
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