Overview of host responses to biomaterials

Nanotechnology Enhanced Orthopedic Materials. http //dx.doi.oi l0.1016/B978-0-85709 44 3.00009-4 

In a broad sense, inflammatory reactions comprise a sequence of events such as acute and chronic inflammations, granulation tissue generation, foreign body reaction, and fibrous encapsulation (or fibrosis). Depending on the implantation process and material 

Implanted biomaterials are usually recognized as foreigners by immune system and inevitably trigger immunological responses that protect host tissue from exposure to such foreigners. In other words, biomaterials may be treated as a kind of pathogens 

Toxicity of biomaterials is usually viewed at both cellular and systemic levels. Toxicity at the cellular level, also known as cytotoxicity, is often caused by direct chemical toxicity of biomaterials, inflammatory reactions, or immune responses to biomaterials. Excessive or severe cytotoxicity, inflammatory reactions, or immune responses may lead to the toxicity remote from the initial insult and affecting organs or organ systems, which is defined as systemic toxicity. It is important to emphasize that toxicity caused by biomaterials is usually dose dependent. For cytotoxicity or nonimmune systemic toxicity, a threshold below which the biomaterial reveals little toxicity may be carefully determined by in vitro and in vivo studies. However, for immune systemic toxicity, determination of such a threshold is extremely difficult because immune responses are individual-dependent and largely affected by properties, dosage, and implantation location of the biomaterials. Toxicity of nanomaterials will be further discussed in this chapter. 

Implant-assodated infection is one of the major reasons behind implant failure, amputation, or even death of patients. Statistics between 2005 and 2006 in the United States reveal that 14.8% of revised total hip arthroplasties were due to infection [3]. 

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