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CHAPTER 13 Medical textiles Anahita 1 Rohani Shirvan1 and Alireza Nouri2,3 Textile Engineering Department, Amirkabir University of Technology (Tehran Polytechnic), Tehran, Iran 2 School of Engineering, RMIT University, Melbourne, VIC, Australia 3 Biomedical Engineering Department, Amirkabir Universi...

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Medical textiles Alireza Nouri Advances in Functional and Protective Textiles

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CHAPTER 13

Medical textiles Anahita Rohani Shirvan1 and Alireza Nouri2,3 1

Textile Engineering Department, Amirkabir University of Technology (Tehran Polytechnic), Tehran, Iran School of Engineering, RMIT University, Melbourne, VIC, Australia 3 Biomedical Engineering Department, Amirkabir University of Technology (Tehran Polytechnic), Tehran, Iran 2

13.1 Introduction Textile materials include fibers, filaments, yarns, and different structures of fabrics are made from natural or synthetic fibrous substances. The applications of textile materials in different fields have significantly increased with the development of new fibers and manufacturing technologies for yarns and fabrics. One of the most important applications of textile materials is in the medical textile industry. This new field is a combination of textile technology and medical sciences with several functional applications. Nowadays, due to the increase of aging populations and the hazards of human activities, including transport accidents, chemical injuries, diseases, sports, etc., the demand for textile-based medical devices have been rapidly growing. These parameters have led to the rapid development of the medical textile market in using novel materials, techniques and technologies to generate modern textile-based materials as medical devices. Generally, textile materials have many unique characteristics such as strength, extensibility, flexibility, air permeability, availability in threedimensional structures, variety in fiber length, fineness, cross-sectional shape, absorbency, etc. These features make them suitable materials for medical applications. However, in some cases, different designs and properties or a combination of several features are required. Therefore it is necessary to improve the characteristics of a product based on its end use. High surface areas, absorbency properties, and large varieties in product forms contribute to the emergence of more smart products in the medical textile industry. Various surface modification and finishing techniques can significantly enhance some specific properties of textile materials such as water and blood absorption, antimicrobial, blood coagulation, wound healing, anticoagulation and so on. Furthermore, by using these modern technologies, we can impart enhanced multifunctional properties to a Advances in Functional and Protective Textiles DOI: https://doi.org/10.1016/B978-0-12-820257-9.00013-8

© 2020 Elsevier Ltd. All rights reserved.

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certain textile-based product. There are different applications for medical textiles including the application inside and outside the body such as wound dressing, hygienic and personal care products, hospital clothes, sutures and textile-based prosthetic and orthotic devices. Extensive progress in tissue engineering and nanotechnology have had a great impact on advanced medical textile products in these areas. On the other hand, the developments of nanomaterials, biomaterials and biotechnology have resulted in fabricating new polymers, hydrogels, composites and fibrous structures with unique characteristics for different medical applications. Consequently, with these improvements in textile and medical industry, the risk of healthcare associated-infection and contagious diseases will decrease. In contrast, patient compliance with medication and treatment and standard of living will increase. The present chapter highlights the key features, common surface modification, and finishing techniques for medical textiles and the main applications of textile-based medical devices in different areas.

13.2 Materials for medical textiles According to the definition of medical textile, the main components for processing of a textile material used for medical applications are fibers, yarns, fabrics, and different types of composites. Mostly, medical textile products are based on five types of fabrics including woven, knitted, braided, laminated, and nonwoven [1]. Recently, using polymers for medical textile applications has increased rapidly because of their unique properties including versatility, biocompatibility, bio-absorbability, and nontoxicity [2]. These materials are considered as the basic constituents for the production of various types of fibers or yarns for the preparation of medical textiles [3,4]. Fig. 13.1 shows the process of medical textile production from polymers. Fibers composed of natural or synthetic polymers are spun into yarns. These fibers are subsequently woven or knitted into fabrics for specific products. An ideal polymer should meet certain requirements for an efficient conversion into a fibrous product; therefore only a few can be made into fibers for manufacturing of medical fabrics. Polymers should be dissolvable or meltable for extrusion, and their chain groups should be linear, long, flexible, and capable of being oriented and crystallized [5,6]. A large number of fibers have been developed over the years by using different natural and synthetic fiber-forming polymers. Cellulose, chitin, and

Medical textiles

Raw materials

Transformations

Fibers

Films

End products

Products (e.g. bone graŌs)

Composites

Polymers

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Yarns

3D Braids

Products (e.g. sutures)

Nonwovens

Products (e.g. protecƟve respirators)

Fabrics Woven/Knits

Products (e.g. apparel)

Laminate fabrics

Products (e.g. waterproof & breathable surgical gowns)

Figure 13.1 Process of medical textile production from polymers.

chitosan, proteins such as gelatin and collagen, alginic acid, and hyaluronic acid are classified in the natural fiber-forming polymers. On the other hand, polyethylene terephthalate, polyamide, polyacrylonitrile, polypropylene (PP), polyethylene, polyurethanes, polyvinylchloride, polyvinyl alcohol, polytetrafluoroethylene, aramid, aliphatic polyesters, polyanhydrides, and polyamino acids are the most important synthetic fiberforming polymers [7,8]. Table 13.1 represents some of these synthetic and natural fiber forming polymers and their applications in the medical field [6,9]. In addition, there are variety of structures that are utilized in technical end uses (Fig. 13.1). For example, laminated fabrics can be made by bonding fabrics with polymeric films or foams via an adhesive for waterproof and breathable surgical applications, where both protection and comfort are essential. Fibers can also be directly processed into nonwoven fabrics via mechanical, thermal, or chemical means. These types of fabrics are desirable for applications in disposable hygiene and protective products such as baby diapers or feminine napkins. Filaments can be braided into three-dimensional braids for specific products such as sutures and ligament prostheses that require exceptional mechanical properties in the longitudinal direction. Fiber-reinforced composites are another structural product that require high tensile and compression

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Table 13.1 Synthetic and natural fiber forming polymers and their biomedical applications [6,9]. Applications

Polymers

Wound care

Polyethylene glycol and agar, xanthan, methyl cellulose, carboxymethyl cellulose, alginate, hyaluronan, and other hydrocolloids Dental materials Hydrocolloids Tissue engineering, Implants Hyaluronan, collagen Technical products Gum Arabic, xanthan, carrageenan, gellan, welan, (cosmetic, pharmaceutical) guar gum, locust, bean gum, alginate, starch, heparin, chitin, and chitosan Drug delivery and Starch, poly(vinylpyrrolidone), poly (acrylic acid), pharmaceutical chitosan, acrylic acid, Injectable polymeric system Polypeptides, chitosan Skin derivatives Highly purified bovine collagen formaline fixed skin Hemostasis Fibrin sealant and foam, chitosan and poly (Nacetyl glucosamine) gels, chitosan adhesives, Suture Collagen, catgut, branan ferulate

strength. Periodontal and bone grafts are two examples of these composite materials in medical applications [6]. An ideal textile material used in medical field should meet some requirements in order to accelerate the healing process, minimize side effects, and enhance patient compliance. Biocompatibility, good resistance to alkalis, acids and microorganisms, good dimensional stability, elasticity free from contaminations or impurities, absorption/repellency and good air permeability are crucial properties in a medical product [10]. Regarding polymeric materials as the main components of medical textiles, their structures and properties have a great effect on the biodegradability, biocompatibility, absorbency, antibacterial property, and other functional performances of the final medical textile products [7].

13.3 Processing of medical textiles Fig. 13.2 represents the manufacturing process of medical textile products. In the first stage, a suitable natural or synthetic polymer based material is chosen and the fiber-forming process is performed via different fiber production methods such as melt spinning, solution wet spinning, solution dry spinning, dry-jet wet spinning, gel spinning, phase separation

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Figure 13.2 Manufacturing process of medical textile products.

spinning, reaction spinning, and electrospinning. In the next stage, yarns are produced via various methods including air-jet, edge-crimping, falsetwist, gear-crimping, knit-de-knit, and stuffer box. Subsequently, fabric manufacturing techniques such as weaving, knitting, braiding, and nonwoven production approaches are used to produce different fabrics with specific structures. In order to achieve the unique characteristics for medical end-use requirements, fibers, yarns, and fabrics are often treated in a number of chemical, physical, and biological processes. In fact, they receive a number of chemical or physical treatments before they are made into a final product. These processes include bleaching, dyeing, finishing, surface modifications, and printing. Recent advances in nanotechnology and materials science have led to the development of surface modification and functional finishing methods for making textiles more resistant to water, stains, wrinkles, and pathogens such as bacteria and fungi. In addition to these treatment processes, medical textiles need to be packaged and sterilized before they can meet the functional and safety requirements of a medical product. Many of dyes and finishing agents have harmful effects on the end users. For example, a number of disperse, acid, reactive dyes, and finishing agents cause allergenic responses when they are in direct contact with the human body. It is therefore important to select

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the most appropriate materials and processes for the treatment of textiles used in medical applications [7,11].

13.4 Engineering of medical textiles In order to improve the performance of medical textiles for different applications, the structural, chemical, mechanical, and physical characteristics of medical textile materials should be engineered by different methods including various types of finishing and surface modifications techniques. In this section, some of the most important modification and finishing methods for medical textiles are reviewed.

13.4.1 Surface modification For all textiles used in medical applications, surface properties play a vital role. Introducing new functional groups, increasing surface energy or wettability, increasing hydrophobicity or hydrophilicity, improving chemical inertness are among the most important advantages of various surface modifications of polymers, fibers, yarns, and fabrics [12]. Moreover, for some specific applications such as implantable devices and scaffolds for tissue regeneration, the bioactivity of polymers is an important feature. Thus by using surface modification techniques, natural and synthetic polymers can be chemically modified to generate improved chemical, physical and biological activities [13]. For this purpose, chemical structures of a polymer can be modified by changing the monomer composition, altering the main chain structure by grafting of side chains, and chemically converting some functional groups on the polymer chains [14]. Some of surface modification techniques have been developed to improve the materials’ characteristics for particular applications. Some of these techniques are briefly discussed in the next section. 13.4.1.1 Surface coating Polymeric coatings will be used to provide long lasting properties on the textiles. These polymeric coatings can be obtained by using polymeric binders often with cross-linking agents in order to withstand better resistance to wear, abrasion, hydrolysis, and repeated washings. Nanocoatings include thin films, nanocapsules, and nanoparticles which are used extensively in biofiltration materials for extracorporeal devices such as artificial kidney, medical fabrics, textile implants, textile substrates for cell growth, and other medical textiles [15,16].

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The most significant aims of using coatings for medical textiles include: • Textile touch and chemical stability • Excellent mechanical properties • Sustainable technology • Ensures safe working environment • Secure and high-quality material supply Electrospun nanofibers, colloidal nanoparticles, nanocapsules, metallic nanoparticles, plasma-sputtered coatings, and cold plasma polymerized coatings are the most common types of coating for textile materials. For instance, various polymeric electrospun nanofibers [17,18] and carbon nanofibers [19,20] are used as suitable coatings for biomedical applications. Via different types of coatings, surface properties such as liquid repellence, stain resistance, antimicrobial activity, odor control, and delivery of biological active agents are added to textiles for medical application. Typically, medical textiles need coatings for protection from blood, body liquid, urine, disinfectants, and other chemical products. There are plenty of coating technologies like spraying, dipping, painting, rolling, etc. Nonetheless, ultrasound and microwave technologies are considered as new methods which can overcome the drawbacks of traditional techniques [21]. Sonochemical deposition is a new coating method which is based on chemical reactions that occurs in liquids under ultrasound irradiation [22].

Bubble formation Nanoparticles Implosion

Micro jets

Substrate

Figure 13.3 Schematic of sonochemical coating of nanoparticles.

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Fig. 13.3 illustrates the schematic of sonochemical coating. Recently, it was shown that the application of sonochemical technique for sustainable surface modification of polyester with TiO2 nanoparticles resulted in durable nanosonofinishing and excellent hydrophobic and antibacterial properties of the fabric [23]. Salat et al. used a single step sonoenzymatic process for coating of cotton medical textiles with antibacterial zinc oxide (ZnO) nanoparticles and gallic acid (GA) to produce biocompatible fabrics with durable antibacterial properties. The ZnO NPs-GA coated fabrics maintained above 60% antibacterial activity even after 60 washing cycles at 75°C hospital laundry regime [24]. In another research by Perelshtein et al., ZnO nanoparticles were synthesized and deposited on the surface of cotton fabrics using ultrasound irradiation for the preparation of antibacterial bandages. This process involves in situ synthesis of ZnO nanoparticles under ultrasound irradiation and its deposition on fabrics in a one-step reaction. The antibacterial test demonstrated a significant bactericidal effect, even in a 0.75% coated fabric [25].

13.4.1.2 Plasma treatment Plasma treatment of textiles is one of the most effective surface modification techniques which creates promising characteristics on the fabric surface for different applications. It is a dry, water-free, and environmentally friendly technique in comparison with conventional solvent-based chemical surface treatment methods [26]. Plasma surface modification has multiple medical applications. It can improve biocompatibility or biological activity on the surface. The main role of plasma technology is the introduction of hydrophilic groups to the textiles which are used as blood filters or filtering membranes for dialysis systems. Another application of plasma treatment is sterilization of medical fabrics which is a less toxic method than ethylene oxide processing, and more cost-effective than irradiation. Via plasma-coated, textiles are presterilized, and save the energy, because the fabric would not have to be sterilized with high temperature and pressure before use. In addition, plasma grafting is a promising technique for the preparation of growth test fabrics, fermentation membranes, implants, catheter fabrics, enzyme-immobilization substrates, and textile grafts. Moreover, plasma-treated fabrics show reduced thrombogenicity and improved healing rate [27]. Fig. 13.4 shows an example of surface activation by plasma treatment. This process generates some functional groups such as hydroxyl, carbonyl, peroxyl, carboxylic, amino, and amines

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Plasma O2

Plasma N2

Figure 13.4 Surface activation of polyethylene by O2 and N2 plasma treatment.

on the surface of the substrate, which not only results in enhanced adhesive strength and permanency, but also leads to a significant improvement in the production of technical fabrics [28]. Plasma treatment as a surface modification technique has gained a great attention in the medical field as a replacement for wet chemical, thermal, and radiative processes. For example, plasma-sputtered yarns and fabrics with silver or silver oxide coatings are considered as an efficient antimicrobial device in medical bandages or wound dressings for burns and ulcers, pressure garments for scars, etc. [29]. In a research, Perˇsin et al. used oxygen plasma treatment for modification of wound dressing materials in order to increase the absorption of wound exudate and blood from the wound site. The microscopic and macroscopic studies showed improvement in the absorption of saline and exudate solutions [30]. Ribeiro and her co-workers used several methods including ultrasound-assisted, dip-coating, exhaustion, and spray deposition for silver nanoparticles deposition on dielectric barrier discharge (DBD) plasma treated and not treated polyamide 6,6 fabric for the production of durable antibacterial textiles. According to the results, ultrasound tip and exhaustion at 70°C showed higher AgNPs loading. Better AgNPs distribution, higher concentration, and less agglomeration were observed in the plasma treated samples [31]. Additionally, plasma treatment can be applied to textile-based implants for different applications. For example, lightweight PP mesh is the most widely used implant among synthetic meshes for hernia repair. However, infection is a big challenge associated to ...