In Vitro Leaching Of Nitinol Medical Devices and Trace Metal Analysis By ICP-MS Spectrometry

Nitinol (NiTi) alloy usage for biomedical implant devices has received significant attention due to its high corrosion resistance, shape memory effect, superelasticity, and damping properties.  In this study, the corrosion behavior of Nitinol alloy was investigated through metal release under physiological condition. Nitinol devices with different shapes, structures or surface layers were leached in Phosphate Buffered Saline (PBS) solution at 37°C under static condition. In vitro trace metal release was monitored with respect to extraction time range from 24 hours (1 day) to 720 hours (30 days).  After leaching, the extracted solutions were analyzed through inductively coupled plasma quadruple mass spectrometry (ICP-MS). The trace metal especially nickel level was observed high within 1 day extraction period and gradually decreases and become stable with time. The result shows that there is 70% change of metal release over 30 days leaching period. The metal content in leaching solution becomes stable over 360 hours (15 days) time period. The minimum 25% change of metal release was observed after 360 hours. Spike recovery experiment was performed during analysis of extracted solution and spike recoveries are in the range of 80-120%.  Trace metal release in different types of extraction vessels were also examined  with different extraction period.