Effect of Vaporized Hydrogen Peroxide and Nitrogen Dioxide Sterilization on Nitinol.

Background: Nitinol is used as the structural framework in numerous types of medical devices (e.g., guidewires, transcatheters, stents). The desire to understand the material compatibility of nitinol with vaporized hydrogen peroxide (VH2O2) and nitrogen dioxide (NO2) sterilization is increasing in healthcare technology. As a result of increased regulatory pressure and capacity limitations related to ethylene oxide (EO) sterilization, the industry is seeking alternative, sustainable sterilization options. Objective: This study sought to characterize the corrosion resistance of nitinol metal alloy wire when exposed to varying levels of VH2O2 and NO2 sterilization. Methods: Scanning electron microscopy (SEM) imaging and energy-dispersive X-ray spectroscopy (EDS) scans were performed to understand the effects of VH2O2 and NO2 sterilization treatments on the surface morphology and chemical composition of nitinol. Results: From the SEM-EDS results, no notable difference was observed when comparing VH2O2 and NO2 test samples with nonsterile control samples. In addition, cyclic potentiodynamic polarization measurements were performed per ASTM F2129-19a to determine corrosion susceptibility. No considerable changes were detected in the electrochemical potential after VH2O2 and NO2 sterilization treatments, when compared with the nonsterile control samples. Conclusion: SEM-EDS and corrosion test results indicated no considerable changes in the surface properties or electrochemical potential of the sterilized samples compared with the nonsterilized control samples. Therefore, nitinol metal showed promising results for compatibility with VH2O2 and NO2 sterilization.

A novel accelerated in vitro release method for biodegradable coating of drug eluting stents: Insight to the drug release mechanisms.

The major objective of the present study was to develop an accelerated in vitro release method for everolimus/poly(lactic-co-glycolic acid) (PLGA) biodegradable DES that reflects and discriminates between many different sources of variations in the manufacturing process by introducing organic solvents in the release medium. To get further insight into the underlying drug release mechanisms, alongside release studies, the surface changes of the coated stents and the molecular weight changes of the polymer upon immersion in the selected release media were examined by scanning electron microscopy and size exclusion chromatography. The incorporation of acetonitrile in the release medium resulted in an increase in the drug release rate due to an increment in total porosity of the matrices. The developed method reflected and discriminated between different sources of variations in the manufacturing process and correlated with the real-time release. Over 80% of everolimus release occurred within 24h. The molecular and gravimetric weights of PLGA remained unchanged throughout the dissolution period, suggesting that the polymer does not undergo degradation through cleavage of its backbone ester linkages. It is likely that the drug release occurred mainly through its diffusion. The method can be employed as a rapid quality control test during development or commercial manufacturing.