Long-term stability of self-assembled monolayers on electropolished L605 cobalt chromium alloy for stent applications

• Published in: Journal of biomedical materials research. Part B, Applied biomaterials Applied biomaterials, 2011-08, Vol.98B (2), p.280-289
• Main Authors: Kaufmann, Christopher, Mani, Gopinath, Marton, Denes, Johnson, David, Agrawal, C. Mauli
• Format: Article
• Language: English
• Subjects: Alloy development; Atomic force microscopy; Biological and medical sciences; Chromium Alloys - chemistry; Chromium Alloys - therapeutic use; Coated Materials, Biocompatible - chemical synthesis; Coated Materials, Biocompatible - chemistry; coatings; Cobalt; cobalt-chromium alloys; Contact angle; Drug Delivery Systems; Drug-Eluting Stents; Medical sciences; Monolayers; Phosphonic acids; Radiotherapy. Instrumental treatment. Physiotherapy. Reeducation. Rehabilitation, orthophony, crenotherapy. Diet therapy and various other treatments (general aspects); Stability; surface characterization; surface modification; Surface Properties; Surgery (general aspects). Transplantations, organ and tissue grafts. Graft diseases; Surgical implants; Technology. Biomaterials. Equipments; X-ray photoelectron spectroscopy
• ISSN: 1552-4973; 1552-4981; 1552-4981
• DOI: 10.1002/jbm.b.31850

Commercially available drug‐eluting stents have the potential to induce inflammatory and hypersensitive adverse reactions due to their polymer coating. The use of self assembled monolayers (SAMs) as an alternate drug delivery platform for stents has recently been demonstrated. In this study, the formation and stability of phosphonic acid SAMs were investigated using the material and surface preparation commonly used to make ultra‐thin stent struts—electropolished L605 Cobalt Chromium (CoCr) alloy. Methyl (CH3) and carboxylic acid (COOH) terminated phosphonic acid SAMs were coated on electropolished CoCr alloy using a combination of solution immersion and dip‐evaporation cycle deposition methods. SAMs‐coated CoCr alloy specimens were thoroughly characterized using contact angle goniometry, Fourier transform infrared spectroscopy (FTIR), X‐ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). These characterizations suggested that uniform and well‐ordered monolayers were coated on the electropolished CoCr alloy. The long‐term physiological stability of monolayers was investigated in tris‐buffered saline (TBS) at 37°C for up to 28 days. Contact angles, FTIR, XPS, and AFM suggested that both CH3 and COOH terminated phosphonic acid SAMs desorb from electropolished CoCr alloy surfaces in a biphasic manner. A significant desorption of CH3 and COOH terminated SAMs occurs within 1–3 days followed by a slower desorption for up to 28 days. Thus, there is a need to develop techniques that can improve the long‐term stability of SAMs on electropolished CoCr alloy for stent and other biomedical applications. © 2011 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2011.