Antimicrobial Treatments Lecture 5 - 2022 PDF

Antimicrobial Treatments Dr Saira Faisal Associate Professor Textile Engineering Department NED UET The Need for Antimicrobial Textiles The microbial attack on textiles results in: Detrimental effects on...

Antimicrobial Treatments Dr Saira Faisal Associate Professor Textile Engineering Department NED UET The Need for Antimicrobial Textiles The microbial attack on textiles results in: Detrimental effects on Odor Formation Contamination risk the consumer Dr Saira Faisal Detrimental effects on Strength Reduction Quality loss the fabric itself DEVELOPMENT OF ANTIMICROBIAL TEXTILES 2 Antimicrobial “ANTIMICROBIAL must kill or stop the growth of microbes & must maintain this property through multiple washes or out door Exposure” Uses Industrial Fabric: That Exposed To Weather, Awning, Tents, Screens, Tarpaulins, Ropes etc Dr Saira Faisal Hospitals Nursing Home Hotels School Sized Fabrics Textiles In Museums Home Furnishings 3 Apparel/Sports Wear Antimicrobial Textiles Fabrication Methods The methods of fabrication of antimicrobial textiles can be classified in two principal categories: Addition of an antimicrobial agent to the polymer before extrusion Dr Saira Faisal Post – treatment of the fiber or the fabric during finishing stages. 4 Development of Antimicrobial Textiles (WEST EUROPE – 2000) Fabrics with antimicrobial Fabrics with antimicrobial post-treatment 26.5 ktons fibers 4.5 ktons Men's Hosiery underwear Others Hosiery 7% 4% Socks 2% Others 1% Socks Lingerie 21% Dr Saira Faisal 27% 25% 19% Men's Shoes underwear Sportswear Sportswear 9% Lingerie 18% lining Shoes 30% 11% 17% lining 9% 5 Antimicrobial Agents Antimicrobials are defined as the agents that either kill microorganisms or simply inhibit their growth. The degree of activity is denoted by: o «-static»: agents that inhibits microorganisms’ growth Dr Saira Faisal o «-cidal»: agent that kill microorganisms This difference is important when dealing with governmental regulations, because biocides are effectively controlled. Textiles with biostatic properties, however, are subject to fewer regulations. 6 Antimicrobial Agents The actual mechanisms by which antimicrobial finishes control microbial growth or kill microorganisms are extremely varied, ranging from preventing cell reproduction, Blocking of enzymes, reaction with the cell membrane destruction of the cell walls and Dr Saira Faisal poisoning the cell Some examples of antimicrobial agents include: Metals and metal salts deactivation of proteins Quaternary ammonium salts membrane damage Others: organic molecules (e.g. Triclosan), natural substances (e.g. chitosan) 7 Requirements for Antimicrobial Finishes Antimicrobial textile finishes must exhibit: Effective control of bacteria, molds and fungi Selective activity towards undesirable microorganisms Absence of toxic effects for both the manufacturer and the consumer Durability of activity to laundering, dry cleaning, leaching Applicability with no adverse effects on the fabric Dr Saira Faisal Acceptable moisture transport properties Compatibility with other finishing agents Easy application, compatibility with common textile processing Must meet strict government regulations and have a minimal environmental impact. 8 Antimicrobials Application Methods Internal Antimicrobial Release: Viable option for synthetic fibers, where antimicrobials can be incorporated into the fibers when they are spun. Surface Application: Dr Saira Faisal Applicable to all fibers. The washing durability depends on materials affinity. Surface application may interfere with textile handling properties. Chemical Bonding: The best way to achieve durability. It requires suitable reactive groups on the textile. 9 Antimicrobials Mechanism An antimicrobial textile can act in two distinct ways: By contact (Non-contact): The antimicrobial agent placed on the fiber does not disperse and to attain the antimicrobial action, microorganisms have to contact the fiber. Dr Saira Faisal By diffusion (leaching): The antimicrobial agent placed on the surface or in the fiber disperses more or less rapidly in a humid external medium to reach the microorganisms and inhibit their growth. 10 Leaching/Non-leaching Dr Saira Faisal 11 Antimicrobials with controlled release or ‘leaching’ mechanism The antimicrobial agents that belong to this category do not form strong bonds with the textile substrate. The chemical species responsible for biocidal activity are released slowly from the treated fabric surface, thus killing all the microbes surrounding the agent. Dr Saira Faisal Advantage their superior antimicrobial activity than compounds based on other modes of action Disadvantage antimicrobial agent in the textile substrate is depleted eventually and loses its effectiveness 12 Metal salts (e.g., silver) and halogenated phenols (e.g., triclosans) are examples of antimicrobial agents that utilize the leaching mechanism Metal salts (silver, copper, and zinc) Silver based antimicrobial agents are broad spectrum antibiotics and are one of the oldest and most widely used biocides. In the presence of moisture silver Dr Saira Faisal releases ions which bind the bacterial cell’s surface with proteins (Figure 1). On binding, the following action occurs Denaturing effect of the silver causes DNA to get condensed and lose its replication abilities. Induces inactivation of bacterial proteins by reacting with thiol group 13 Halogenated phenols (Triclosan) Triclosan is a phenyl ether with broad spectrum antimicrobial action which is employed in a great number of everyday household and personal care products including plastics, fabrics, soaps, Dr Saira Faisal deodorants, toothpaste, and cosmetics. Triclosan, when exposed to sunlight in the It inhibit the growth of microbes by environment, breaks down into 2,8- penetrating and disrupting the cell wall of dichlorodibenzo-p-dioxin, which is chemically microbes related to other toxic polychlorinated dioxins. When added into polymer, it migrates to the Owing to such health and environmental surface and protect the material issues, a number of leading retailers as well as triclosan is biocidal, however, at a low governments in Europe are concerned about or concentration acts as biostatic reagent have banned the “unnecessary use” of 14 triclosan in textiles and some other products Bound or non-leaching type antimicrobials The antimicrobial agents that belong to this category are chemically bound to the textile substrate. Hence, the antimicrobial can act only on the microbe that comes in contact with the treated textile’s surface. By virtue of its binding nature, these antimicrobials do not get depleted and Dr Saira Faisal therefore potentially may have higher durability However, compounds on a treated fabric might get abraded or deactivated with long term usage and lose their durability The antimicrobial agents listed under this category are: Quaternary ammonium compounds Chitosan 15 Quaternary Ammonium Compounds QAC’s typically possess a silane base at one end of the molecule and a long molecular chain of carbon atoms at the other end. the silane base of the compound reacts with the fabric and forms a covalent bond. The other end is projected out and is positively charged. Dr Saira Faisal When a microbe approaches the fabric the free end of the agent’s molecule reacts with the cell wall and causes a leakage of the negatively charged species in the microbe cell. It eventually causes the cell’s death. When the negatively charged bacteria cells contact the positive quaternary amine charge (N+ ), the electric balance is disturbed and the bacterium could explode under its own osmotic pressure. Long cationic polymers can penetrate bacterial cells to 16 disrupt membranes, like needle bursting balloons  Chitosan Chitosan is a non-toxic, biodegradable, natural polysaccharide. The only difference between chitosan and cellulose is the amine group in the position C-2 of chitosan instead of the hydroxyl group in cellulose. Chitosan inhibits bacteria growth. Chitosan can form insoluble network (through its amino or hydroxyl groups). Dr Saira Faisal Due to the reactive hydroxyl groups chitosan can be chemically bound on cellulose through common durable press finishes. The advantages of the antimicrobial finish with chitosan include high absorbency properties, moisture control, promotion of wound healing, non-allergenic, non-toxic and biodegradable properties. it is effective against microorganisms only at higher concentrations and forms a film on the surface of the fabric which decreases the air permeability; and the fabric becomes stiff after its application Mechanism studies suggest that the positively charged chitosan interacts with negatively charged residues at the cell wall of fungi or bacteria. The interaction changes cell permeability and causes the leakage of intracellular substances 17 Other studies suggest that the formation of the polymeric substance around the bacterial cell prevents the nutrients from entering the cell Comparison of different antimicrobial agents Dr Saira Faisal 18 Examples of inherently antibacterial synthetic yarns Dr Saira Faisal 19 Antimicrobial Activity Tests Textile fabrics: Determination of the antibacterial activity: Agar diffusion plate test SN 195921-1992 Textile fabrics: Determination of the antimycotic activity: Agar diffusion plate test AATCC 30-1993 Antifungal activity, assessment of textile materials: Mildew and rot resistance of textile materials Dr Saira Faisal Agar diffusion tests, semi-quantitative AATCC147-1993 Antibacterial assessment of textile materials: Parallel streak methods AATCC 90-1982 Antibacterial activity of fabrics, detection of: Agar plate method AATCC 174-1993 Antimicrobial activity assessment of carpets JIS L 1902-1998 Testing method for antibacterial of textiles AATCC 100-1993 Antibacterial finishes on textile materials: assessment of Challenge test, SN 195924-1983 Textile fabrics: Determination of the antibacterial activity: Germ count method quantitative 20  Results Dr Saira Faisal 21