title: Strain-induced crack formations in PDMS/DXA drug collars.
abstract: Drug-eluting systems are currently used in cardiac leads in order to reduce inflammation and fibrosis at the lead-tissue interface. Drug release from these drug delivery systems can be modulated by the manufacturing processes used to create the drug systems and assemble them onto the cardiac lead. In this study, scanning electron microscopy, atomic force microscopy and Raman microscopy are employed to explore the material characteristics of a polydimethylsiloxane-dexamethasone acetate drug collar used on cardiac leads when varying the strain during collar assembly on the lead. A novel test fixture was created in order to investigate these drug collars under simulated stresses. Measurements of the collar while fitted to a rod revealed microcracks that are hypothesized to affect the drug release performance, resulting in increased drug elution. It was found that the strain that occurs during assembly of the collar onto the lead is a key factor in the formation of these microcracks. Results also suggest that cracks tend to form in areas of high drug particle density, and propagate between drug particles.
authors.affiliation: Characterization Facility, University of Minnesota, Minneapolis, MN 55455, USA. jawarner@umn.edu
authors.forename: J A
authors.initials: JA
authors.lastname: Warner
authors.forename: J C
authors.initials: JC
authors.lastname: Polkinghorne
authors.forename: J
authors.initials: J
authors.lastname: Gonerka
authors.forename: S
authors.initials: S
authors.lastname: Meyer
authors.forename: B
authors.initials: B
authors.lastname: Luo
authors.forename: C
authors.initials: C
authors.lastname: Frethem
authors.forename: G
authors.initials: G
authors.lastname: Haugstad
mesh_terms: D019245:Compressive Strength; D003907:Dexamethasone / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000737:chemistry; D004058:Diffusion; D004129:Dimethylpolysiloxanes / Q000737:chemistry*; D054855:Drug-Eluting Stents; D055119:Elastic Modulus; D004567:Electrodes, Implanted; D006244:Hardness; D008422:Materials Testing; D009757:Nylons / Q000737:chemistry*; D013314:Stress, Mechanical; D013499:Surface Properties; D013718:Tensile Strength
chemical_list: D004129:Dimethylpolysiloxanes; D009757:Nylons; C085707:poly(dimethylsiloxane)-polyamide copolymer; D003907:Dexamethasone; C018038:dexamethasone acetate