Implantable textiles materials

Figure 10.1 Some examples of implantable textile materials.

Nanofibers have applications in medicine, artificial organ components, tissue engineering, implant material, drug deliveiy, wound dressing, and medical textile materials. Nanofiber meshes... 

Textile materials are used in a wide variety of applications in healthcare and medicine which include implantable materials for in vivo applications. Vascular grafts, artificial ligaments, artificial blood vessels and mesh gra are typical implantable medical devices. High-tech advances in tissue engineering have enabled researchers to cultivate implantable hiunan organs to the required shape by growing living cells on textile sc olds. 

Medical textiles embrace all those textile materials used for medical devices in health and hygiene plications in both the consumer and medical markets, thus comprising a group of products with considerable variations in terms of product performance and unit value. Categories of medical textiles include non-implantable materials, implantable materials, healthcare and hygiene products, and extracorporeal devices. The application of different fibres for fabricating medical textiles for medical devices is illustrated in Tables 1-3, which focus on non-implantables, implantables, and healthcare/hygiene, respectively. 

Because textile materials are lightweight, flexible and strong polymers and biological tissues are themselves fibrous polymers, with very similar dimensional, physical and mechanical properties, they have found numerous applications as bioimplants. From their use as sutures and ligatures many thousands of years ago, to hernia repair meshes and vascular grafts in the present century, textiles continue to be explored for use in newer and better performing medical products. The currently available implants can be categorized as one-, two- or three-dimensional structures. 

For textiles to perform life-support and life-saving functions, they must remain functional in the environment of the body over a predicted period of time. The material selected should be chemically stable and physiologically acceptable and it should have optimum physical and mechanical properties. It must be defect-free, uniform in size and predictable in tensile and other properties. There are, therefore, both general requirements for a textile material before it can be selected for construction of an implant, as well as specific requirements, such as optimum strength, flexibility, abrasion resistance and long-term patency, which may vary from product to product. The last major section in the chapter discusses the general requirements for implant success and the key properties needed to optimize physical performance. 

Fibers rub against each other in assemblies when stretched, bent or sheared. Textile materials also rub against tissues and bones when used as implants. The friction and adhesion involved in such contacts cause surface damage, which adversely affects the long-term performance of an implant. Also, the particles generated by the friction/adhesion processes can cause a reaction and lead to inflammation of the surrounding tissues. Consequently, the ability of polymers and fibers to resist abrasion damage is an important... 

Although the range of textile materials is very large, focusing on implantable devices narrows the scope. Chemical biocompatibility is an essential requirement. A close look reveals that only about 50 materials are commonly used compared to more than 1.5 Mio materials that exist. This shows how necessary it is to take into account chemical constraints of implantable medical devices to meet the requirements of standards and regulatory processes (Table 13.3). 

For many years, textile structures have been successfully used for wound treatment, operations and implants. The popular range of these products include plasters, wound gauze, dressing material, surgical stitch material, vessel prosthesis and hernia nets. There is a differentiation between external and internal (implant) application. Most products are woven or knitted textile materials, which, for the various applications, are made up according to individual requirements. Figure 12.1 illustrates an embroidered stent. 

Biocompatibility investigations on artificial blood vessels made from polyethylene terephthalate show good in-vivo tissue compatibility. Investigations of porous, textile blood vessel implants show that connective tissue formed within 28 days within the textile material. However, this tissue differs from normal connective tissue. With increasing implantation time, a reduction in molecular mass has been observed bursting strength was reduced to 25% after 13.5 years, which is considered sufficient for this application [988]. 

Biocompatibility is of prime importance if textile materials are to be accepted by the body. In this respect, four key factors will determine how the body reacts to the implant. 

Textile materials are particularly suited for implants because they are usually biocompatible materials that can be made into two- or three-dimensional structures, with mechanical characteristics adapted to the environment. The properties can also be adjusted by controlling the macroscopic structure of the textile materials and by specific surface design. Table 2.3 shows some examples of implantable materials. 

Starting from plain cotton-based products, medical textiles have seen rapid development over the last few decades. Nowadays, new biodegradable fibers have enabled the development of novel types of implants, and modem textile machines can produce three-dimensional spacer fabrics that give superior performance over traditional textile materials. These and many other advances have made medical textiles an essential element in modem disease management, and they are becoming more and more important with the increasing number of elderly people in the populations of developed countries. 

As the basic component of medical textile materials, the structures and properties of the constituent polymers have a significant effect on the biodegradability, biocompatibility, absorbency, antimicrobial property, and other functional performances of the final medical textile products. Functional modifications of polymers have far-reaching effects on the fibers, yams, fabrics, and textile materials that are processed in a series of downstream operations. In order to generate the desired product performance characteristics for their diverse applications such as hygiene, protection, therapeutic, nonimplantable or implantable materials, extracorporeal devices, etc., the chemical and physical structures of the relevant polymers should be engineered to suit their required specifications. 

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