Microbiologically Stable Fibres: An Overview

Abstract:

Microbiologically steady strands are impervious to microbiological specialists, along these lines delaying their existence and benefiting the earth. Conditions were set down by the scientist  for getting fibers of such category. As per the set conditions fibers should be non-cancer-causing, strong, non-allergenic and nontoxic. If the fibers have powerful antibacterial activity, it must release scent in very less amount for developing protected and solid piece of clothing.In another way we can also say that for making healthy, comfortable and safe garment, odour must be reduced by the fibers. To develop antimicrobial property, compounds like bivalent hydroxide and tetravalent metal phosphate, are being incorporated in the fibers. There is a new fiber like Amicor which is based on acrylic fiber, with the same type of behaviour. It should be noted that the antimicro-biological agent has capacity to provide protection against larger pests like dustmites, bacteria and fungi. Due to abrasion, weathering and so forth, there become loss of surface agent which is further replaced by the incorporated agent which migrates from inside to the outer surface of the fiber. The present paper provides extensive review on developments in the application and characterization of microbiologically stable fibres for various applications in the healthcare and allied area.

Introduction:

In current scenario people have been very health centric that’s why they choose the products which are good in hygienic and durable. Textile is the product category which you can find everywhere. You can say that human beings start their lives with textile and end up with textile. So hygienity alongside solidness is significant worry for some material items which individuals utilize the greater part of time. The textile products which people use for daily purposes  are mostly threatened by microbs/fungi and other insects. So technologists  are involved in their research to make textile products for long lasting durability against harmful microbes. A new generation fiber is Amicor, which has antibacterial property and being used for many textile products such as mattresses, bedding, bedsheets , pillow, blanket, quilt, carpets, leggings, socks, denim, towels, baby care products etc. Researchers have also claimed to develop tetravalent metal phosphate incorporated fiber. There has been made in use of an organic substrate having very fine particle size for getting effective antimicrobial characteristics without deteriorating original features of fiber.

Many times due to humid and hot environment socks produce bad smell due to action of bacteria and fungi which tends to reduce its strength after prolonged exposure to bacterial environment. Natural fibers  like cotton easily affected by bacteria/fungi as compared to synthetic fibers. The acrylic based Amico fiber developed by blending with cotton to increase stability of the Amicor- cotton based products.

Mostly synthetic non-biodegradable fibers are used for the stability against microbs, but there exist  biomimetic textiles obtained from different methods of functional finishing, fiber processing and fiber orientation[1], and biopolymers obtained from sea weeds like sodium alginate obtained from algae[2] have characteristics to stabilize in microbial environments.

There are various chemical methods which are being employed for making textile fibers stable in bacterial environments. These methods are incorporation of antibacterial agent in the fibers and antibacterial finishes on the textile substrate. Antibacterial agents reduce the colonization of bacteria and this helps to reduce the effect of bacteria. Newly developed antimicrobial fibers like Amicor TM, Rhovyl AS has significant properties to be used in commertial products. Functional finishes for improving antibacterial activities are silver nanoparticle finishes, insect proof finishes, plasma finishes, chitosan based finishes and anti bacterial finishes etc. These chemical processes reduce the activity of bacteria/fungi and prevents from  odors and itching.

Adherence of microbes:

For research groups including food and medical industries, adherence of bacteria to the surface has emerged as a vital topic. Studies for bbacterial adherence are done in broad range of subjects such as synthetic and natural fibres[3,6-10], surgical sutures[11], glass[12],contact lens  [4,5] surgical grade metals and implants[13], dental restorative materials[14], urinary catherators[15], hydrocarbons[16], sand[17] and stainless steel[18]. Generally solid-liquid interface is prone to adherence of microbes. Aavailability of nutrients and substratum for colonization by bacterial cells are advantages of such site of interaction [19]. Mutual interaction of microbes and substrate play an important role in adherence of microbial agents. Variation in attributes of microbial cell surface, substrate surface and interacting medium between the two affect the interaction of microbes and substrate [19,20].

There are some prime features of microbial cells regarding adherence:

1. a) Charge on cell-surface of microbiological agent.
2. b) Hydrophobicity of microbial cell surfaces.
3. c) Receptors of cell.
4. d) Microbial cells’ ability of forming slime or biofilm.
5. e) Dependency of cell surface nature on carbon-to-nitrogen ratio of growth.
6. f) Centrifugation parameters.
7. g) pH, composition and ionic strength of suspending media of cell.

Some important physico-chemical characteristics which affect the adherence of microbes:

1. a) Hydrophobic and Hydrophilic nature of fabric.
2. b) Fabric surface charge
3. c) Structure and surface roughness of fabric
4. d) Temperature and relative humidity of the environment in which fabric is going to be used.
5. e) Composition of fabric and fiber content
6. f) Surface treatment of the

Biofilms on a substrate formed by adhered microorganisms can not be treated as biofilms so easily as it provides protection against any harsh physical or chemical treatments [13]. Microbial adherence mechanism: Interaction between substrate and microbial cells is not an easy process. It involves many kinds of forces and interactions. Some interactions are of long range and some are of short range. Long range interactions are effective when the distance between microbial cells and substratum becomes more than150 nm and for short range interactions, distance should becomes less than 3nm [20]. In broad way microbial interaction can be divided into two phases; Reversible phase involves the physicochemical interaction under forces like electrostatic forces, hydrophobic forces, Vander-wall forces, Brownian motion, gravitational forces while in irreversible phase, more specific interaction occurs in which cell surface of microbes plays a vital role. The extracellular structures and secretions like Fimbriae, flagella, slime, EPS, LPS , outer membrane proteins, antigens O and H, M protein on cell wall are responsible for holding substratum and in this interaction, hydrogen bonding, covalent bonding and ionic interaction are responsible forces[18,20] . With the help of Classical Derjaguin Landau-Verwey-Overbeek (DLVO) theory or XDLVO theory, interaction of bacteria and their adhesion to solid surfaces can be explained and it  can also be applied in bacterial interaction and their adhesion models, among which XDLVO theory also considers Lewis acid-base interaction other than electrostatic interaction and Lifshitz-vander-wall interaction for estimating net interactions of bacterial adhesion to inert solid surfaces[17,21].  There are following steps for bacterial adherence on fabric:

1. At first few microbial cells contact with fabric.
2. Initial bacterial cells forms micro colonies on fabric surface.
3. biofilm is formed by coalescing neighbouring colonies.
4. stains, foul smell and pigmentation on fabric appear.
5. bio degradation of fabric occurs

Influence of microbial adherence on textile products:

Due to presence of cellulosic constituent in natural fibers,  these are affected by various types of bacteria like Cellvibrio, Cellulomonas, Sporocytophaga, Cytophaga, Clostridium Bacillus[22]. Several species belonging to genera Pseudomonas, Actinomycetes and Bacillus are known to be responsible for degradation of wool fiber[22]. Streptomyces, Serratia, Pseudomonas are genera of bacterial species which are responsible for degradation of silk fiber[22].

Followings are the important effects of bacterial adherence on fabric.

1. Bacterial growth on fabric causes discolouring or staining, discolouring of material.
2. After establishment of bacterial population there are chances of altering cloth pH, which can be responsible to change the colours of fabric material or dyes.
3. Bacterial growth can be cause of fibre degradation reducing elasticity and tensile strength of textiles.
4. Bacterial growth on fabric can be cause of formations of substances such as amines and acids.
5. Bacterial infection and its development in fabric can be responsible for several diseases such as eczema, allergies, etc.
6. Bacterial infested textile materials which are infested by bacteria can cause of spreading pathogens.

Amicor ,a stable fiber against bacteria & fungi:

AmicorTM is a specialty anti-microbial fibre available from Thai Acrylic Fibre Limited. It was developed by Acordis (UK) in late 1990s and is protected by two patents. It was manufactured using patented intelligent fibre technology. AmicorTM is specifically engineered to incorporate additives into the core of fibre. It promises durable & long lasting anti-microbial function upto 100 washes. Figure1 is showing the cross-sectional view of Amicor fiber.

Figure 1. Amicor fiber cross-section reproduced from apparelviewsbd.com

Intelligent Fibres for the 21st Century should be anti-bacterial, anti-fungal, anti-dust mites and related allergens, durable, long lasting action, gentle, safe and soft and  applicable to all textile applications.They are expected to be  dyeable to brightest and most delicate shades using AmicorTM.

It is available as a staple fibre or as a continuous tow. It is a blend fibre that needs to be used at between 20% to 30% of the composition of the article. It can be converted into products by all conventional techniques- yarn spinning, nonwoven processes etc. It dyes and finishes like a regular acrylic fibre/yarn and offers exceptional durability – up to 100 washes.

Its Anti-microbial testing is performed by Internationally recognized protocols JISL 1902:2002 against Staphylococcus aureus and Klebsiella pneumoniae. It can also test AmicorTM for  effectiveness against other bacteria/fungii upon request .

Certification criteria:

• Seal of Approval’ from the British Allergy Foundation
• Oeko Tex Standard 100 Class 1 Certified
• REACH SVHC Certified
• Fully compliant with BPR legislation

The average person spends as much as one-third of their lifetime in bed . It is very important to ensure a safe environment in bedrooms and AmicorTM ensures a fresh and safe bed feeling every time, every single time of its use, It helps to prevent fungal spores from developing which in turn helps to prevent dust mites from colonizing the bedding article. These two factors reduce allergens from building up in the bedding article. It assures complete sleep protection for you & your family[25].

Amicor in Denims:

According to the presentation of Aditya Birla Group, when a sample of denim which was composed of 70% cotton and 30% Amicor TM fabric whose warps were 100% cotton and wefts were 100% AmicorTM, was studied for 20, 50 and 100 washes for Staphylococcus Aureus and Klebsiella Pneumoniae and discovered that the reduction of both types bacteria after the 20, 50 and 100 washes were 99.95 and 99.98% respectively. JISL 1902:2008 test method was used to find adherence of bacteria. Due to excellent antibacterial behaviour of Amicor TM it is also used in athletic shoes, carpets and hotel towel[25].

Advantages of Amicor:

– Long durability as active ingredients are embedded inside the fibre (Upto 100 washes)

– Uniformity of the application

– Compatible with all types of garment finishes except coatings.

_ Reduces the chance of Asthama due to the prevention of House Dust Mites.

Antibacterial Activity of Rhovyl AS:

For test purpose Polyvinyl chloride Rhovyl AS (Figure2) was chosen as an object as it displays antibacterial activity by the introduction of Triclosan directly into the polymer melt of this fibre [27,28]. Like other Polyvinyl Chloride fibers, Rhovyl AS also does not sustain fire, and gets negatively charged after being rubbed against human skin it is electrified. This negative ionisation, in turn, causes expansion of the blood vessels on the surface of the body, thus improving the circulation of blood and having a positive effect on body temperature [29]. The end-use properties of Rhovyl AS are supplemented by its physical and mechanical characteristics; the breaking strength of the fibre is 13-16 cN/tex. Rhovyl AS is manufactured in a range of linear density from 2.4 to 5.6 dtex and staple length from 26/32 mm to 70/110 mm, which enables the fibre to be processed by various spinning techniques.

Figure 2. Rhovyl Laine chlorofiber blended with wool reproduced from old.swicofil.com

The results of the antibacterial activity tests of the blanket fabrics shows that the fabrics are characterised by high bacteriostatic and bactericidal activity regardless of the percentage and amount of Rhovyl AS in the weft.  Antibacterial activity of the grey blanket fabrics with Rhovyl AS in their weft after 2, 4, 6, 8, and 10 washings were studied. It was seen that the bacteriostatic activity was slightly lower after 2washings, but the level of activity remained unchanged after further washings. The bactericidal activity(Figure 3.), however, can be regarded as retaining the same level, since the values 3.1 and 3.4 were within the interval of confidence for values describing the amount of bacteria on the sample. All in all, the above results indicate permanent biological activity of the Rhovyl AS fibres imparted to them by washings, but the level of activity remained unchanged after further washings.  All in all, the above results indicate permanent biological activity of the Rhovyl AS fibres imparted to them by Triclosan added to the polymer melt. Micro-biological tests of the bacteriostatic and bactericidal activity of the blanket fabrics made with varied proportions of Rhovyl AS were conducted at the Microbiological Laboratory of the Institute of Chemical Fibres, Łódź.

Figure 3. Effect of wet washing on bacteriostatic and bactericidal activity of blanket fabric made with Rhovyl AS reproduced from Natalia Sedelnik,  Health-Promoting Properties of Blankets Made with the Bioactive Fibre ‘Rhovyl AS’ in the Pile, Institute of Natural Fibres ul. Wojska Polskiego 71 b, 60-630 Poznañ, Poland, 2002.

Anti-bacterial agents:

It has been found that some metals have antibacterial activities in their ionized form. Ag, Cu and Zn ions are utilized as antimicrobial agents. Stability and releasing of ions are the main concerns when it is incorporated in the fibers or applied as coats or finishes. To overcome these difficulties researchers are trying to develop various methods to improve antibacterial activities of the ions. Metal phosphonates are applicable in chemical synthesis as catalysts, in gas separation as solid sorbents, in electrochemical devices as material and in drug delivery as matrices[31]. Titanium having monolayer of phosphonate containing silver had biocompatibility as well as antibacterial properties[32]. From various studies, it can be concluded that silver ion can perform coactively with other antibacterial substances, including Zn2+[33]. Even dead antibiotics can be revived and can protect from MRSA with full capacity when combined with silver[34].

According to tests performed for antimicrobial activity and cytotoxicity,  AgZn–TCP and AgCu–TCP had better performance when compared with Ag–TCP and b-TCP, and AgZn-TCP showed low cytotoxic behaviour[30].

Natural fibers having stability against bacteria:

Hemp:

It is one of the most versatile natural fibers(Figure 4.) having antibacterial activity, durability, resiliency and functionality of natural AC.  After extraction with ethyl alcohol antibacterial property of hemp fiber decreases[24]. After about four hours inhibition rate of Candida albicans, E-coli, and Staphylococcus aureus reach equilibrium stage[24]. By the help of different experiments like UV and FTIR, it was found that hemp contains chalcone[24]. Saponins, alkaloids, and flavones may antibacterial constituents in hemp fiber[24] . Hemp has also very advantageous properties in perspective of environmental pollution that, it requires very less amount of water and no requirement of synthetic fertilizers, pesticides, herbicides or genetically modified seeds to grow .

Figure 4. Hemp fiber reproduced from indiamart.com

Bamboo Fiber:

Bamboo(Figure 5.) is known for its eco-friendlyness and multifunctionality. It is said that Bamboo clothing contains antimicrobial properties but the scientific evidence regarding this is very less but it is being sold in the market on the name of this property. Extracts of bamboo plant grown in Australia were analyzed for its antibacterial properties[35]. Two types of samples were prepared; one is prepared with 20% aqueous solution of DMSO and another sample was prepared with 90% aqueous solution of dioxane. The antibacterial properties of both the samples were studied for Escherichia coli and found that second sample gave  better result, and antibacterial agent exists in lignin[35]

Flax:

Flax(Figure 6.) comes in the category of bast fibre. This fiber is known to be favourable for the skin of human beings. By affecting physiological parameters, Linen fabric gives high comfort to end users. Flax fiber is breathable for human epidermis , less allergic and antibacterial. But it is to be pointed out that there is less number of literatures available in which antibacterial properties are precisely described. Chemical composition of fibers get influenced by extracting method and there exists different level of antibacterial properties of fiber[23]. Clinical strains of Staphylococcus aureus is used to estimate biological properties of flax fibers[23]. Nike, Sara and Modran are the varieties of flax which give very good results against bacteria due to highest constituent of lignin [23].

Figure 5. Bamboo fiber reproduced from indiamart.com

Figure 6. Flax fiber reproduced from textilelearnerblogspot.com

Conclusion:

In future the role of microbiologically stable fibers is going to be very crucial because of changing need of customer with respective to hygiene. Today harmful bacteria and viral attack has created a challenge for researchers to develop protective clothing for the safety of human being.  The application smart fibers such as  Amicor and Rhovyl AS which release metal ions and reduces the bacterial growth .Emerging methods of surface finishing of textile materials with the use of Silver, Copper and Zinc ion  has created a new benchmark . The use of such metal based material is effective against the microbes but creates additional load on the environment and skin irritation problem to the user. It becomes need of hours to develop more sustainable formulations based on the natural resources in order to have  better effectiveness both for product and environmental ecology.

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Authors Name and Designation