The Tissue—Implant Interface

Implantation of a synthetic material into mammalian living tissue causes a number of biological host responses, including rejection by the body, encapsulation in newly formed fibrous tissue, and successful incorporation into surrounding tissues. The fate of an implanted device is determined by cellular 

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Interactions at surfaces and interfaces also play an essential role in the design and function of clinical implants and biomedical devices. With a few recent exceptions, implants do not attach well to tissue, and the resulting mobility of the tissue-implant interface encourages chroitic inflammation. The result can be a gathering of platelets at the site, leading to a blood clot or to the formation of a fibrous capsule, or scar, around the implant (Figure 3.3). 

Amorphous zone A region of the tissue-implant interface immediately adjacent to the implant substrate. This zone is of variable thickness (usually <1000 A), is free of collagen, and is comprised of proteoglycans of unknown composition. 

The composition and structure of scaffolds used in tissue engineering are aitical for successful implantation into the host s injury site. An accelerated stable implant fixation with reduced risk of infection significantly reduces the physical suffering, psychological impact, and health care cost of patients. Biochemical methods for immobilization and/or delivery of proteins, enzymes, or peptides at the tissue-implant interface have been employed at devices that can induce controlled and rapid healing. 

Acute inflammation normally resolves quickly, usually less than 1 week, depending on the extent of injury at the implant site. However, the presence of acute inflammation (i.e., PMNs) at the tissue/implant interface at time periods beyond 1 week (i.e., weeks, months, oryears) su ests the presence of an infection. 

A minimal response is generally called fibrous encapsulation and the implant is encapsulated within fibrous tissue containing mainly collagen with a few fibroblasts. At the tissue/implant interface, a one to two cell layer of macrophages and foreign body giant cells is present which constitutes the foreign body reaction. 

The pure PLA scaffold lacked sufficient mechanical, electrical and bioactive properties, mainly for application in bone tissue regeneration. Poor integration between implant and surrounding bone can cause detrimental wear debris, as well as stress and strain imbalances at the tissue-implant interface. 

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