title: An investigation of adhesion in drug-eluting stent layers.
abstract: An atomic force microscopy (AFM) method was developed to quantify the adhesion forces between and cohesive forces within the layers of a drug-eluting stent (DES). Surface pairs representing both the individual components and the complete chemistry of each layer within the DES were prepared. As a model, the CYPHER Sirolimus-eluting Coronary Stent was studied. This DES consists of a stainless steel stent substrate, a parylene C primer layer, and a drug-eluting layer that contains poly(ethylene-co-vinyl acetate), poly(n-butyl methacrylate), and sirolimus (rapamycin). Coated AFM tips and two-dimensional substrates or coupons, which act as surrogates to the CYPHER Stent, were prepared and characterized. The force-displacement measurements were conducted to evaluate the adhesion between the middle parylene C layer and the 316L stainless steel substrate, the adhesion between the parylene C layer and the outer drug-eluting layer, and the cohesion between the three constituents of the drug-eluting layer. The average adhesion forces between the parylene C to drug layer varied from 88 to 167 nN, and the drug layer-to-drug layer interactions were between 194 and 486 nN within the model CYPHER Stent coating. All the adhesion forces measured were larger than those observed for gold-gold interactions, which yielded a pull of force of 19 nN (Zong et al., J Appl Phys 2006;100:104313-104323).
authors.affiliation: Cordis Corporation, A Johnson and Johnson Company, Welsh and McKean Roads, P.O. Box 776, Spring House, Pennsylvania 19446, USA. kwolf8@crdus.jnj.com
authors.forename: Kurt V
authors.initials: KV
authors.lastname: Wolf
authors.forename: Zong
authors.initials: Z
authors.lastname: Zong
authors.forename: Juan
authors.initials: J
authors.lastname: Meng
authors.forename: Argjenta
authors.initials: A
authors.lastname: Orana
authors.forename: Nima
authors.initials: N
authors.lastname: Rahbar
authors.forename: Karin M
authors.initials: KM
authors.lastname: Balss
authors.forename: George
authors.initials: G
authors.lastname: Papandreou
authors.forename: Cynthia A
authors.initials: CA
authors.lastname: Maryanoff
authors.forename: Wole
authors.initials: W
authors.lastname: Soboyejo
mesh_terms: D000268:Adhesiveness; D000900:Anti-Bacterial Agents / Q000737:chemistry; D020099:Coated Materials, Biocompatible / Q000737:chemistry*; D054855:Drug-Eluting Stents; D008422:Materials Testing; D018625:Microscopy, Atomic Force; D011108:Polymers / Q000737:chemistry*; D020123:Sirolimus / Q000737:chemistry*; D013193:Stainless Steel / Q000737:chemistry*; D014992:Xylenes / Q000737:chemistry*
chemical_list: D000900:Anti-Bacterial Agents; D020099:Coated Materials, Biocompatible; D011108:Polymers; D014992:Xylenes; D013193:Stainless Steel; C011055:parylene; D020123:Sirolimus