Chapter Three - Oxidative Stress, Inflammation, and the Corrosion of Metallic Biomaterials: Corrosion Causes Biology and Biology Causes Corrosion

Abstract

Oxidative stress, inflammation, and the respiratory burst occur when phagocytic cells are stimulated to respond to infection or the presence of a foreign material. They are major factors in how the body responds to metallic biomaterials. However, until recently, the study of the biocompatibility of metallic medical devices has focused primarily on the toxicity of metal cations and the generation and consequence of metal-based particle debris resulting from the oxidation side of metal corrosion reactions. In this chapter, the interplay between corrosion and biology is refocused to explore several newly recognized interactions that arise between metals engaging in electrochemical processes (oxidation and reduction associated with corrosion) and the biological system (which is rich in redox processes including respiratory burst and the generation of reactive oxygen species). Reduction reactions at metal surfaces induce cellular apoptosis when cells are cultured directly on cathodically polarized metal surfaces, and inflammatory cells, using ROS and oxidative burst, can corrode implant surfaces in a far more aggressive fashion than was previously understood. Together, these insights expand the concept of biocompatibi­lity for metallic biomaterials in vivo and more clearly define a zone of electrochemical viability (ie, a voltage range within which cells remain viable, and outside of which they die). Overall, the interplay between metals and biology are far more complex than previously appreciated and results in two-way positive feedback between corrosion and biology.