The Effects of Surface Properties on the Antimicrobial Activity and Biotoxicity of Metal Biomaterials and Coatings

Biomaterial-related infection has serious consequences since it compromises the function and durability of many fixation devices and joints. This impacts the physiological and psychological wellbeing of the patient, and results in increased costs and an increased burden on resources. Antimicrobial metal and alloy surfaces and coatings are becoming commonplace as a potential solution to reduce the risk of biomaterial-related infection. However, despite much research and advances in the development of biomaterials made from metals and alloys, infection rates continue to rise. The development of antimicrobial biomaterials is difficult, since there are a number of factors that influence antimicrobial activity, and these factors also invariably affect the biotoxicity of the implant. Such factors include the surface properties (topography, chemistry and physicochemistry) and where the implant is to be positioned in the body (e.g., open or closed environment). Furthermore, the type of surface and biological factors will influence the deposition of proteins and biomolecules from the surrounding milieu, and their orientation on the surface. The adsorption of the conditioning film onto the surface can also affect interactions between the bacteria and the biomaterial interface. The interaction between the environment and the metal or alloy surface will also affect the corrosion rates of the material. In addition, differences in the bacterial genus and species also influence the antimicrobial efficacy of the biomaterial. Consideration must be given to obtain a balance between the optimal surface properties to maintain the structural integrity of the implant, reduce bacterial binding, induce the antimicrobial activity, and ensure that the biomaterial has minimal cytotoxic effects. This chapter considers the effects of the surface properties of metal surfaces and alloys on microbial binding and the subsequent antimicrobial and biotoxicity properties of metal and alloy biomaterials.