In the last few decades the use of implants that are replacing a living organ or an injured tissue is growing up. A biomaterial is defined as a medical device, intended to interact with biological systems. Any material that is implanted into a living organism triggers the host diffencive system, which will attack it and try do destroy it.
Cited from Guy Sovak PhD Thesis:
Bone Tissue Reaction to a Novel Titanium Nitride (TiN)
Coating on Titanium Alloy (Ti-6al-4V) Implants
and the Effect of Growth Factors and
Cell Adhesion Molecules.