Correlation of in-Vitro Assessments of Pitting Corrosion to Uniform Corrosion in Nitinol Stents
Tuesday, May 13, 2014: 1:00 PM
Merrill Hall (Asilomar Conference Grounds)
Dr. Srinidhi Nagaraja
,
Food and Drug Administration, Silver Spring, MD
Dr. Maureen Dreher
,
Food and Drug Administration, Silver Spring, MD
Mr. John Bouck
,
Food and Drug Administration, Silver Spring, MD
Ms. Lynn Chen
,
Food and Drug Administration, Silver Spring, MD
Dr. Jiwen Zheng
,
Food and Drug Administration, Silver Spring, MD
Ms. Katie Miyashiro
,
Nitinol Devices & Components, Fremont, CA
Ms. Christine Trépanier
,
Nitinol Devices & Components, Fremont, CA
Mr. Payman Saffari
,
Nitinol Devices & Components, Fremont, CA
Dr. Alan R. Pelton
,
Nitinol Devices & Components, Fremont, CA
There is public health need to understand the effects of corrosion in nickel containing medical devices. Corrosion of these devices may result in adverse events such as loss of the implant’s mechanical integrity and nickel sensitization. This is important for Nitinol devices where nickel is approximately half of the elemental composition and its corrosion resistance is highly dependent on manufacturing processes. However, it is unclear how proposed acceptance criteria for resistance to pitting corrosion in vitro (i.e. using ASTM F2129) correlate with other in-vitro corrosion assessments such as immersion testing. This study aims to address the knowledge gap by manufacturing stents with different surface treatments in order to elucidate the relationships between benchtop tests for pitting and uniform corrosion. Generic stents manufactured by NDC were processed using common manufacturing techniques of thermal oxidation (Air Furnace and Salt Pot groups), mechanical polishing, and electropolishing to target specific corrosion resistances based on breakdown potentials measured by ASTM F2129 testing.
Stents from each processing group were immersed in acid washed containers of PBS at 37C. At baseline,1,2,3,5,7,14,21,30,45, and 60 days, aliquots of the solution were analyzed with ICP-MS to assess nickel ion release. Interim results showed a significantly greater (p<0.007) nickel release in Salt Pot and Air Furnace stents compared to Mechanical Polished stents out to 14 days. At 14 days, cumulative nickel release was 161 ppb for Salt Pot, 108 ppb for Air Furnace, and 15 ppb for Mechanical Polish. Relationships between processing methods, surface characteristics, and benchtop results will be discussed.
