title: Detailed analysis of polymer response to delivery balloon expansion of drug-eluting stents versus bare metal stents.
abstract: OBJECTIVE
  We sought to describe the response of the polymer surface of drug-eluting stents (DES) to delivery balloon expansion, including quantitation of any resulting detached microparticles.
  
  
  RESULTS
  We expanded the US Food and Drug Administration (FDA)-approved first- and second-generation DES in a vacuum filtration system and used optical and scanning electron microscopy to image the polymer surface, filters and delivery balloons. DES were expanded under a range of conditions, from in vitro conditions used for FDA regulatory submissions to human in vivo conditions. Dispersive Raman spectroscopy was used for definitive identification of microparticles. All polymer surfaces were topographically disturbed over an average of 4.6%-100% of the surface area imaged. Disturbances ranged from deformation (including peeling) to complete delamination. The dimensions of detached microparticles were 2-350 μm. The extent and nature of surface disturbances and microparticles were primarily a function of polymer composition (p<0.001 for 8/10 disturbance types/locations) and were independent of expansion condition (p=0.100 to 0.989 for 9/10 disturbance types/locations).
  
  
  CONCLUSIONS
  Balloon expansion of first- and second-generation DES disturbs the polymer surface and can cause detachment of microparticles; each is functionally related to the specific polymer but not to expansion condition. Disturbance "roughness" and detached microparticles may contribute to DES limitations.
authors.affiliation: Division of Cardiovascular Medicine, Duke University Medical Center, Durham, NC 27710, USA. scott.denardo@duke.edu
authors.forename: Scott J
authors.initials: SJ
authors.lastname: Denardo
authors.forename: Paul L
authors.initials: PL
authors.lastname: Carpinone
authors.forename: David M
authors.initials: DM
authors.lastname: Vock
authors.forename: James E
authors.initials: JE
authors.lastname: Tcheng
authors.forename: Harry R
authors.initials: HR
authors.lastname: Phillips
authors.forename: Bradley J
authors.initials: BJ
authors.lastname: Willenberg
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Batich
authors.forename: Carl J
authors.initials: CJ
authors.lastname: Pepine
mesh_terms: D015906:Angioplasty, Balloon, Coronary / Q000009:adverse effects / Q000295:instrumentation*; D062906:Cardiac Catheters; D054855:Drug-Eluting Stents; D008422:Materials Testing; D008670:Metals; D008855:Microscopy, Electron, Scanning; D061848:Optical Imaging; D010316:Particle Size; D011108:Polymers / Q000737:chemistry*; D011312:Pressure; D011474:Prosthesis Design; D011475:Prosthesis Failure; D013059:Spectrum Analysis, Raman; D015607:Stents; D013499:Surface Properties
chemical_list: D008670:Metals; D011108:Polymers