Natural antibacterial agents and their applications

In recent years, with the enhancement of people’s awareness of hygiene and safety, antibacterial and deodorant processing has developed rapidly in various functional finishing of fibers and textiles, and antibacterial textiles have been widely used in people’s daily lives. The antibacterial agents currently used can be roughly divided into three categories: inorganic, organic and natural antibacterial agents. Inorganic antibacterial agents mainly include silver zeolite, silver silica gel, silver activated carbon, etc. Organic antibacterial agents include quaternary ammonium salts, guanidines, organometallic compounds, etc. However, the chemicals used in the above antibacterial finishing agents can easily cause environmental pollution and have certain harmful effects on human health. With the increasing awareness of environmental protection and the popularity of green textiles, the use of natural substances to make textiles with antibacterial properties has attracted more and more attention. Under the influence of returning to nature and environmental awareness, natural antibacterial agents will become the first choice for antibacterial textile production in the future.

1. Types and characteristics of natural antibacterial agents

Natural antibacterial agents are mainly derived from extracts of natural substances and can be roughly divided into three categories: animal, plant and mineral.

1.1 Animal antibacterial agents

Among the natural antibacterial agents, those belonging to animals mainly include chitin, chitosan and insect antibacterial proteins.

Representative animal natural antibacterial agents include chitin and chitosan. Chitosan (Chitosan) is extracted from natural crab shells, shrimp shells and insect shells and is refined through deacetylation. It has excellent broad-spectrum antibacterial properties and is effective against Escherichia coli, Bacillus subtilis, and Grapevine aureus. It has the ability to inhibit cocci and Pseudomonas aeruginosa, and has properties such as hygroscopicity, breathability, biocompatibility, biodegradability, biological activity, chelating properties and enzyme curing effects.

There are roughly two proposed antibacterial finishing mechanisms of chitosan:

①The amino cations of chitosan [2] attract each other and anions such as sialophospholipids that constitute the microbial cell wall. As a result, the freedom of the microorganisms is restricted and their metabolism and reproduction are hindered;

② A large amount of low molecular weight chitosan invades the microbial cells and prevents the microbial genetic code from replicating from DNA to RNA, thus hindering the reproduction of microorganisms. Chitosan has the ability to inhibit Escherichia coli, Bacillus subtilis, Staphylococcus aureus and Pseudomonas aeruginosa.

In addition, chitin also has many applications. Chitin powder is added to chemical fiber yarns, or chitin fiber is blended with other fibers to produce textiles with antibacterial and health care effects. Because it does not contain chemicals and metal components, it can be used as a high-end green antibacterial textile.

Insect antibacterial proteins are an aspect of biotechnology used in the textile industry. There are more than 150 kinds of antibacterial proteins isolated from insects. Insects have strong adaptability to the environment and are highly resistant to invasion by microorganisms such as bacteria and viruses. . The antibacterial proteins secreted from their bodies are heat-resistant, have broad antibacterial properties, and have a certain effect on drug-resistant bacteria.

1.2 Plant antibiotics
Natural antibacterial agents that belong to plants include juniper, mugwort, aloe, etc. There are many domestic studies on the dyeing of plant dyes in textiles and the application of synthetic antibacterial agents on fabrics. Researchers from Dalian Institute of Chemical Physics, Beijing Institute of Fashion Technology, Suzhou University and other units are working on natural dyes such as rhubarb, licorice, and skullcap. , coptis, gardenia, lithospermum, turmeric, catechu, mulberry, hematoxylin and other dyeing research. Its plant species are mainly divided into the following categories.

1.2.1 Hinoki tar
Juniper oil can be distilled from cypress. It is a light yellow oil and consists of two components, namely, the neutral oil of sesquiterpene compounds as the essence of flavor and the phenolic acidic oil with antibacterial activity. Acidic oil contains hinokitiol (or hinokitiol), and the main component of neutral oil is axoprene. The antibacterial mechanism of cypress oil is that there are two oxygen atoms available for coordination and complexation in the molecular structure, which interact with proteins in microorganisms to denature them. It has a wide range of antibacterial properties, especially has a strong killing effect on fungi. Its acute toxicity LD50[1] is 1500 mg/Kg (orally administered to mice), and its skin irritation is quasi-negative.

1.2.2 Mugwort
Mugwort is a perennial herbaceous plant of the Asteraceae family. It is a traditional custom in my country to hang mugwort during the Dragon Boat Festival to repel insects and prevent diseases. The smell of mugwort has a calming effect that stabilizes your mood and relaxes your body and mind. The main components of mugwort include 1,8-aminodenephrine, a-sulfone, acetylcholine, choline, etc. They have antibacterial, anti-inflammatory, anti-allergic and promoting blood circulation effects.

1.2.3 Aloe
Aloe is a plant in the Liliaceae family, with more than 300 species. It can be roughly divided into two types: medicinal and ornamental, such as sunflower aloe, shale aloe and acupuncture aloe. Aloe vera, which has medicinal properties, has been used in medicine, cosmetics and health food. The medicinal ingredients of aloe mainly include polysaccharides and phenolic ingredients. Aloin, which plays a major role, has antibacterial, anti-inflammatory and anti-allergic effects. In recent years, aloe vera extract has just begun to be used on fabrics as an antibacterial agent.

1.2.4 Licorice
Licorice is a perennial herbaceous plant of the Leguminosae family, mainly produced in China and Afghanistan. It is often used as a crude drug in traditional Chinese medicine and is a medicinal herb that has long been recognized by people. The main component of licorice is glycyrrhizin, which has a sweet taste, and its sweetness is sucrose.150 times of the acid hydrolysis to generate glycyrrhetinic acid, glucuronic acid and flavonoid glycosides, etc. It has anti-inflammatory, anti-mutative, anti-ulcer and detoxifying effects. It has low toxicity and is safe for human body.

1.2.5 Wild vegetables
Amaranth, commonly known as Houttuynia cordata, is a perennial herbaceous plant of the family Poraceae. The medicinal ingredients in the leaves and stems of amaranth mainly contain decanoyl acetaldehyde and methyl nonyl ketone lauric acid. It has strong antibacterial effect against Staphylococcus aureus and linear bacteria. Because of its high safety, it is used as a fabric health care and comfort processing agent.

1.2.6 Tea
Tea contains a variety of chemical components, mainly polyphenolic compounds, alkaloids (caffeine), catechins, etc. Studies have shown that catechins have inhibitory effects on microorganisms such as Streptococcus and Staphylococcus aureus. It also inhibits the activity of tyrosine decarboxylase. In addition, it has many medicinal functions such as antiviral, fungicidal, detoxifying and anticancer.

1.2.7 Pomegranate peel
Pomegranate is a deciduous shrub of the Pomegranate family, native to Iran. The peel can be used as medicine. Its extract can inhibit collagenase activity and can be used to develop ecological antibacterial fabrics with high consumer performance. Its pigment components can be used as direct dyes for cotton fabrics and Antibacterial finishing. Experimental results from Japan’s Metropolitan Hygiene Research Institute show that when the dyeing concentration is above 50% (based on fabric weight), pomegranate dyeing has antibacterial power and durability that meets the evaluation standards of the Sanitary Processing Association. In addition, the dye fastness complies with the JIS bath towel dye fastness standards. Therefore, Japan is developing pomegranate as an ecological antibacterial finishing agent that does not pollute the environment.

Many other plants have certain antibacterial properties, such as skullcap, coptis, phellodendron, hematoxylin, madder, chrysanthemum, comfrey, mustard extract, pepper, garlic, etc. We need to dig more and study them.

1.3 Mineral natural antibacterial agents
Among the natural antibacterial agents, there are antibacterial agents extracted from minerals, such as: gall vitriol, realgar, etc. Bile alum has a strong inhibitory effect on pyogenes, Shigella dysenteriae and Salmonella; realgar has a strong killing effect on a variety of skin fungi and intestinal pathogenic bacteria. Minerals with antibacterial effects have a long history of use as pharmaceuticals, but their application in textiles is still in the exploratory stage. The “Melma” processing method launched by Shikishimabo in Japan to produce products with skin protection functions is the application of natural minerals. It crushes natural minerals into powder and fixes them inside the fiber. The products produced by this method have good washability, good slipperiness, and moisturizing effect. They are especially effective in resisting or blocking allergies and allergens.

2. Application of natural antibacterial agents in textiles

2.1 Processing methods of antibacterial fabrics
There are two main processing methods for producing antibacterial fabrics using natural antibacterial agents: raw fiber processing and post-processing.

The fibril processing method, also known as the antibacterial fiber method, is produced by using physical modification, chemical modification, composite spinning and adding antibacterial agents to the spinning solution to spin fibers. Chemical modification technology is divided into grafting method and ion exchange method. The fiber made by ion exchange has a long-lasting antibacterial effect because the metal ions form ionic bonds with the ion exchange group of the fiber; antibacterial agents are added to the spinning solution It is the main means to develop antibacterial fiber. The fiber fabric processed by this method has the advantages of good antibacterial effect and long-lasting effect, but it is difficult to control the particle size of the finishing agent particles. Composite spinning is an antibacterial masterbatch and raw materials made from antibacterial agents. Fibers with a sheath-core structure are made through composite spinning. The antibacterial masterbatch is used as the skin layer and the raw material is used as the core layer. In the antibacterial fiber obtained by this method, the antibacterial agent is only distributed in the cortex of the fiber. Therefore, compared with the method of adding antibacterial agents to the spinning solution, less antibacterial agents are required, which can reduce the impact on the physical and mechanical properties of the fiber and the impact of the introduction of antibacterial agents on the fiber. Performance impact.

Post-finishing processing method is a method that uses dipping, padding, coating and other methods to apply antibacterial agents on the surface of fibers during the printing, dyeing and finishing process of textiles and fix them on the textiles to achieve antibacterial effects. The advantage is that processing It is simple. The disadvantage is that the antibacterial agent only exists on the surface of the fiber, is not resistant to washing, has a large amount of initial dissolution, and has problems with wearing safety. The dipping method (padding method) and surface coating method are mainly used.

One of the main methods currently used to treat fabrics with natural antibacterial agents is microencapsulation technology. This technology is to wrap one or several active ingredients of natural antibacterial extracts in microparticle capsules, and then fix them in the fibers of the fabric, making it a health care fabric. Some of the capsules in the fibers burst when they come into contact with the skin. Emits fragrance and antibacterial agents, etc. play its health care role. For antibacterial microcapsules, the composition and thickness of the wall material can usually be changed to control the release rate of the antibacterial agent in the microcapsules. Extended durability. When applied, the microcapsules can be combined with textiles through coating processing or padding method together with fixing agents.

2.2 Application of antibacterial textiles
Antibacterial textiles have a wide range of applications. Specifically, they can be used in the following aspects.

(1) Used in shirts, summer clothes, skirts, baby clothes, and sportswear. Using antibacterial fiber to make clothing can effectively solve the problem of sweat odor, bacterial growth and bacterial infection, and reduce�To prevent the occurrence of infectious diseases, enhance one’s own resistance to bacteria and create one’s own healthy environment.

(2) Applied to underwear. It can play an antibacterial, wicking, moisture-conducting, and deodorizing role to achieve healthy effects. It has the effect of improving local hygiene, eliminating body odor, conducting moisture and deodorizing.

(3) Used in socks and various footwear. Using antibacterial fiber in shoes and socks can improve the reproduction of bacteria on the feet, inhibit bacterial growth, wick away perspiration, conduct moisture, and deodorize. It can also help prevent dry feet, sweaty feet, and cracked feet.

(4) Used in bedding, towels, bath towels, blankets, carpets, and decorative fabrics. Prevent the growth of bacteria, mites, skin infections and other diseases. So the antibacterial function is very useful.

(5) Antibacterial non-woven fabrics made of antibacterial fibers are used in hospital bedding, laboratories, surgical sterile clothing, and doctor and nurse uniforms. It can effectively solve the cross-infection between people, people and things, and things and things, and achieve the purpose of scientific prevention.

(6) When applied to automobile decorative cloth, a new concept of antibacterial automobiles can be obtained.

(7) Reinforcing cement with antibacterial short fibers can not only improve the strength of the cement, but also make the concrete antibacterial. It can be used in public places such as parks, wards, and zoo walls where bacteria are prone to breed.

(8) In the air-conditioning appliance industry, using antibacterial fiber non-woven fabrics as filters can greatly reduce the reproduction of bacteria and reduce the number of washing times of air-conditioning filters.

3. Development Trend

3.1 Fabrics made from antibacterial fibers are superior to post-finished fabrics in terms of antibacterial effect and durability. Therefore, the development of new antibacterial fibers with permanent antibacterial effects is a new trend in textile research.

3.2 Since fabrics treated with nano-antibacterial finishing agents have excellent washing resistance, efficient and long-lasting antibacterial effects, and have advantages that other embedding agents cannot match, the development of nano-finishing agents is a hot topic in antibacterial finishing today.

3.3 Antibacterial finishing that makes the fabric have multiple functions of hygiene, health care, comfort and easy storage at the same time, and strengthens the multiple finishing effects of mildew prevention, ringworm prevention, etc.

3.4 Chitosan has attracted much attention due to its good antibacterial effect, biodegradability, and large storage capacity in nature. Therefore, chitosan will play a huge role in the production of textiles.

4. Conclusion

In recent years, with the continuous rise of green consumption concepts and the in-depth promotion of clean production, natural antibacterial agents, with their unique charm of rich resources, biodegradability, and good absorption properties, cater to the consumer psychology of returning to nature and maintaining health and fitness. Therefore, The development and research of “green” health-care natural antibacterial agents have far-reaching significance. Of course, the safety of using natural antibacterial agents should also be cautious. Natural ones cannot be considered absolutely safe. Therefore, textiles treated with natural antibacterial agents must be inspected before being put on the market.

China has rich reserves of animal, plant and mineral resources, and has thousands of years of experience in the application of Chinese herbal medicine. Therefore, the development of natural antibacterial agents for textiles that meet social needs is a major trend. If our country’s existing resources are rationally developed, then we will be in the field of antibacterial finishing. Can be among the best in the world.

Reference:

[1] LD50 (lethal dose 50%) is the half-lethal dose (LD is the abbreviation of Lethal dose), which refers to the dose of poison used to cause half of the experimental animals to die within 14 days after being exposed to the poison once. It is generally expressed in milligrams of poison per kilogram of body weight. For example: LD50=0.1mg/kg means that after one-time ingestion of a toxic substance at a dose of 0.1mg*BW (body weight), half of the animals tested will die within 14 days.

[2] NBIO® natural chitosan antibacterial agent (functional principle: due to the amino group (-NHз) and hydroxyl group (-OH), it has antibacterial and moisturizing effects, protects the skin, and forms a skin film through natural polymer substances to achieve thermal insulation/BIO fusion Patented new technology).