Engineering biocompatible implant surfaces: Part I: Materials and surfaces

During recent decades vast and continuously increasing numbers of biomedical implants have been introduced for continuous use in the human body. Since the early cemented hip replacements in the 1960s there has been a constant spread of new materials, and ever more complex designs are being used in these implant devices. But still the rate of failure and loss of implants is undesirably high and leaves space for improvements. The challenge is to understand the interactions of implant surface with the surrounding tissue sufficiently, to actively tailor desired interactions. Bulk and surface properties of biomaterials used for implants have been shown to directly influence, and in some cases, control the dynamic interactions that take place at the tissue–implant interface. It is critical to recognize that synthetic materials have specific bulk and surface properties or characteristics that determine their in vitro and in vivo characteristics. This article reviews the interdisciplinary field of biocompatible implant surfaces from the viewpoint of materials science, biochemistry and cell biology. It compiles an overview on basic information about bulk and surface properties of implants based on metallic materials (particularly titanium and its alloys) and surface modification including functionalization with adhesion and growth promoting species. It describes how cells recognize surfaces and respond to different biomaterials, outlines common assays on cell behavior in culture, and reports on cell types and proteins involved in tissue response, acute and chronic responses to implanted biomaterials.