The introduction of coated drug-eluting vascular stents in recent years necessitates additional evaluation of the device coating. The shedding of the coating from the stent can alter its clinical safety and/or therapeutic benefit. For example, drug elution may be affected by particle generation from the coated stent system and from coating defects.
ISO 25539-2, ASTM F2743-11 and FDA Guidance Documents provide guidance for coating inspection and particulate characterization of intravascular stents and delivery systems. They include guidelines for inspection of the coating at various intervals throughout the test as well as both acute and chronic particle characterization while the device is being deployed and then tested.
Using a Scanning Electron Microscope (SEM) with automated particle size analysis and Energy Dispersive Spectroscopy, MDT is able to take these inspection and characterization requirements to a new level. In addition to providing SEM photos for coating inspection and particle size analysis, we also provide valuable information about the particle composition. This comprehensive approach provides several key advantages to MDT customers including:
SEM Photography to a Magnification of 100,000x: These photos can be used for inspecting the coating integrity prior to, during and after completion of the test. These SEM capabilities can also be used for:
Particulate Size Characterization: Leveraging an advanced tool called Automatic Feature Analysis (AFA), the SEM provides information regarding the number and sizes of the particles. Both the SEM Photography and this capability satisfy the requirements of ISO 25539-2 and ASTM F2743-11.
Particle Composition Characterization: Combining the AFA software with the built-in EDS sensor, the SEM provides information regarding the particle composition. Although not a requirement of the ISO and ASTM specifications, this capability provides key insights regarding potential material risks for both the medical device and deployment system.
Quick Turnaround: Since MDT has this capability in-house, it is able to provide these services on a fast turnaround basis. Inspections can be performed while the durability test is running.
Fixture Design: MDT's particle counting modules can be integrated with our Stent/Graft Test Systems. Individualized flow loops, flow meters, and filters are provided for the mock vessels. MDT's flow loop design minimizes the flow compliance effect so that physiological radial strains for fatigue testing are maintained. Click here for a white paper on our method for acute particle characterization.