Implantable fibers

This functionalization of the fibrous implantable device, which allows to meet specific needs in particular biological environments, needs to correlate the microstmcture and nanostructure scales of fibers to the scale of the desired cells that we desire for the adhesion. As cell adhesion occurs on the fiber length, fibers diameter should be optimized to ensure high adsorption surface ratio while being adjusted to cell dimensions that can vary from nanometers to hundreds of micrometers. Fiber process technologies are nowadays able to cover this range and provide implantable fibers with diameters from millimeters, such as suture filaments, to nanometers, by electrospinning process (Fig. 13.2). 

The surface of fibers was investigated by the methods of light and electronic microscopy in order to clarify the reasons for the loss of mechanical properties of fibers and increase in their brittleness. At an earlier time of implantation fibers morphology remains basically unchanged. Cracks appear after 5 months. The development of cracks accelerates on the surface of libers during the first year. 

Figure 1 Historical milestones in the development of wound dressings, antimicrobial fibers and implantable fibers.

Health Safety. PET fibers pose no health risk to humans or animals. Eibers have been used extensively iu textiles with no adverse physiological effects from prolonged skin contact. PET has been approved by the U.S. Eood and Dmg Administration for food packagiug and botties. PET is considered biologically iuert and has been widely used iu medical iaserts such as vascular implants and artificial blood vessels, artificial bone, and eye sutures (19). Other polyester homopolymers including polylactide and polyglycoHde are used iu resorbable sutures (19,47). 

Bicomponent technology has been used to introduce functional and novelty effects other than stretch to nylon fibers. For instance, antistatic yams are made by spinning a conductive carbon-black polymer dispersion as a core with a sheath of nylon (188) and as a side-by-side configuration (189). At 0.1—1.0% implants, these conductive filaments give durable static resistance to nylon carpets without interfering with dye coloration. Conductive materials such as carbon black or metals as a sheath around a core of nylon interfere with color, especially light shades. 

Although silk and cotton are classified as nonabsorbable sutures, these do lose strength gradually in living tissue and slowly break up after long periods of implantation (18). The USP specifications for Class I nonabsorbable sutures (silk or synthetic fibers) are shown in Table 4. 

Other surgical implants are essentially plastic repair products for worn out parts of the body. It is possible to conceive of major replacements of an entire organ such as a kidney or a heart by combining the plastic skills with tissue regeneration efforts that may extend life. This is used to time the heart action. Extensively used are plastic corrugated, fiber (silicone or TP polyester) braided aortas (24). 

Figure 1 shows the results of those experiments. It is important to recognize that in this experiment the polymer was present in a form affording high surface area when compared to other studies where rods, pellets, plates, fibers, and so forth were used. It is often quite difficult to compare exact degradation times from various independent studies due to differences in implant surface area and... 

Both types are hydrophobic materials that, depending on the side group arrangements, can exist as elastomers or as microcrystalline fiber- or film-forming materials. Preliminary studies have suggested that these two classes of polyphosphazenes are inert and biocompatible in subcutaneous tissue implantation experiments. 

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