Artificial graft

As promising as Yannas s original formulation was, it suffered from one major problem. In a patient who is severely burned, there may not he enough healthy skin tissue available to harvest the epidermis needed to replace the silicone coating on the artificial graft. Yannas s solution to this problem was to develop an artificial epidermis that could he implanted at the same time as the artificial dermis. 

Furthermore, meshes have been composed of multilayers consisting of different polymers. Matsuda and coworkers produced bilayer meshes of a thick polyurethane microfiber mesh and a thin nanofiber mesh composed of type I collagen. The material decouples mechanical properties from the biochemical functionality of collagen to form a prototype scaffold for artificial grafts [194],... 

The major interest in calcium phosphate cements has always been in their potential for biomedical applications. This is because bone contains hydroxyapatite (Ca5(P04)30H), a calcium phosphate mineral. Any material that could be used to bond bone or produce an artificial graft should contain this mineral for compatibility. In fact, much of the research in producing calcium phosphate-based cements or sintered ceramics was motivated by their biomedical applications. We will discuss applications of calcium phosphate cements in detail in Chapter 18. This section describes their materials development. 

This brief description of processes in bone indicates that it is chemically very active. For this reason, the objective of research in bioceramic is to mimic the internal processes and the structure of bone with man-made materials. Once placed, there should be little distinction between the natural bone and man-made ceramic implant or an artificial graft. 

Vascular grafts are used to replace, bypass, or maintain function of damaged, occluded, or diseased blood vessels. They can be obtained through the use of either blood vessels of the patient s own body (autogenous grafts) or synthetic materials (artificial grafts). 

The most used materials to manufacture artificial grafts are polyethylene tere-phthalate (PET, Dacron ), polytetrafluoroethylene (PTFE), and PUs. The first PU vascular graft was a polyester-based PU (Vascugraft ). These prostheses showed good biocompatibility but a poor chemical stability in Also polyether-based PUs... 

Matsuda T, lhara M, Inoguchi H, Kwon IK, Takamizawa K, Kidoaki S. Mechano-active scaffold design of smaU-diameter artificial graft made of electrospun segmented polyurethane fabrics. J Biomed Mater Res A 2005 73A 125-31. 

V. Steger, M. Hampel, I. Trick, M. Muller, T. WaUes, Clinical tracheal replacement transplantation, bioprostheses and artificial grafts. Expert Rev. Med. Devices 5 (5) (Sqrtember 2008) 605-612. 

Tubular scaffolds fabricated by electrospinning have been extensively studied as scaffolds for small diameter (<6 mm) vascular grafts. Current artificial grafts, mainly Dacron and expanded polytetrafluoroethylene (ePTFE), have had some success when used in larger diameter grafts but are limited by issues such as thrombosis when considered for use in smaller diameter grafts. Electrospun tubular scaffolds can be fabricated with well-controlled diameters and uniform thickness across the material. The variety of polymers from which these scaffolds can be synthesised has resulted in scaffolds with mechanical properties similar to those of native vascular tissues, and hence these better support blood flow and capillaiy in-growth. 

Endothelial progenitor cells (EPCs) are a particular cell type of extreme importance in the regeneration of endothelial and cardiac tissue. Current evidence suggests that EPCs may be recruited by the use of specific molecules such as small peptides or antibodies (Camd-Unal et al, 2010,2012 Hatch et al., 2011). This strategy could help to treat cardiovascular injuries using circulating EPCs to accelerate the re-endotheUaUzation process of artificial grafts and other related cardiovascular TE applications. 

Other than generating artificial grafts for orthopedic interface repair, hydroxyapatite has been incorporated to the screws as an osteoconductive component used for fixation... 

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