title: Drug delivery from gold and titanium surfaces using self-assembled monolayers.
abstract: Currently available drug-eluting stents (DES) use polymers for coating and releasing drugs. Increasing evidence suggests that inflammatory and hypersensitive reactions are caused by such polymer coatings. This study focused on developing new techniques for delivering drugs directly from metal implant surfaces. Hydroxyl-terminated self-assembled monolayers (SAMs) were coated on Au and Ti surfaces. Therapeutic self-assembled monolayers (TSAMs) were prepared by chemically attaching the model drug, flufenamic acid, to SAM coated metal surfaces. Three different methods of esterification (acid chloride esterification, dry heat esterification, and direct esterification) were explored to attach flufenamic acid to SAMs. TSAMs were characterized using X-ray photoelectron spectroscopy, fluorescence microscopy, atomic force microscopy, and contact angle goniometry. These techniques collectively confirmed the attachment of drug onto SAM coated metal surfaces. In vitro drug release was investigated by immersing TSAM coated metal specimens in tris-buffered saline (TBS) at 37 degrees C for 28 days. TBS was analyzed at 1, 3, 7, 14, 21, and 28 days for the amount of drug eluted using high performance liquid chromatography. Large data scatter was observed for the release profiles of TSAMs prepared by acid chloride esterification. TSAMs prepared by dry heat and direct esterification methods showed an initial burst release of the drug followed by a sustained slow release for up to 2 weeks. Thus, this study suggests the potential for using self-assembled monolayers as an alternate system for delivering drugs from coronary stents and other metal implants.
authors.affiliation: Department of Biomedical Engineering, College of Engineering, The University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249-0619, USA.
authors.forename: Gopinath
authors.initials: G
authors.lastname: Mani
authors.forename: Dave M
authors.initials: DM
authors.lastname: Johnson
authors.forename: Denes
authors.initials: D
authors.lastname: Marton
authors.forename: Marc D
authors.initials: MD
authors.lastname: Feldman
authors.forename: Devang
authors.initials: D
authors.lastname: Patel
authors.forename: Arturo A
authors.initials: AA
authors.lastname: Ayon
authors.forename: C Mauli
authors.initials: CM
authors.lastname: Agrawal
mesh_terms: D002851:Chromatography, High Pressure Liquid; D020099:Coated Materials, Biocompatible / Q000737:chemistry*; D016503:Drug Delivery Systems / Q000295:instrumentation / Q000379:methods*; D004951:Esterification; D005439:Flufenamic Acid / Q000737:chemistry; D006046:Gold / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D008856:Microscopy, Fluorescence; D013057:Spectrum Analysis; D013499:Surface Properties; D013997:Time Factors; D014025:Titanium / Q000737:chemistry*
chemical_list: D020099:Coated Materials, Biocompatible; D005439:Flufenamic Acid; D006046:Gold; D014025:Titanium