Oxide Layer Formation, Corrosion, and Biocompatibility of Nitinol Cardiovascular Devices

Nitinol-based cardiovascular devices can undergo corrosion following placement in the body and the resulting corrosion events may have potential implications on the mechanical integrity and biocompatibility of the device. This review article summarizes the critical factors that influence the degree to which Nitinol devices are susceptible to in vitro and in vivo corrosion, the extent of nickel release from the device, and the potential adverse biological effects following nickel release from the device. In particular, local and uniform corrosion resistance of the device is related to the quality of the protective surface oxide layer that is established by heat treatments and common surface processing techniques during device fabrication. Further, Nitinol implants in the cardiovascular system may be subjected to mechanical loading (pre-strain, fatigue, and fretting) and interact with different metals that can impact the corrosion behavior of the material. Biological responses that may occur following nickel release from Nitinol devices, such as cytotoxicity, thrombus formation, local effects on vascular tissue, systemic effects, and hypersensitivity, are discussed in this review. In addition, the use of computational biokinetic models in the absence of experimentally derived data to estimate local and systemic nickel concentrations in the body is discussed.