The concept of biocompatibility can be divided into principles: biosafety and biofunctionality (Kirkpatrick et al. 1998). The biosafety principle requires materials to “not, either directly or through the release of their material constituents: (i) produce adverse local or systemic effects, (ii) be carcinogenic, or (iii) produce adverse reproductive and developmental effects” (FDA 1995). On the other hand, biofunctionality concerns the performance of a given material in application to a particular tissue; in this regard, biofunctionality can be defined as “the ability of a material to perform with an appropriate host response in a specific application” (Williams 1987). An example that illustrates these two principles is the biocompatibility requirements for orthopedic implants: for the biosafety requirement, these devices need to be made of materials that are nontoxic; for the biofunctionality requirement, bone-forming cells must be able to adhere to the surface of the implant materials to promote bone growth.