title: Biodegradable polymer brush as nanocoupled interface for improving the durability of polymer coating on metal surface.
abstract: Metal-based drug-eluting stents (DESs) have severe drawbacks such as peeling-off and cracking of the coated polymer. To prevent the fracture of polymer-coated layer and improve the durability of DES, poly(l-lactide) (PLLA) brushes were synthesized onto cobalt-chromium (Co-Cr or CC) surface through atom transfer radical polymerization (ATRP) of 2-hydroxyethylmethacrylate (HEMA) followed by surface-initiated ring opening polymerization (SI-ROP) of l-lactide. The polymer brushes were then characterized by attenuated total reflection-Fourier transform infrared (ATR-FTIR), water contact angle, ellipsometry, X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and scanning electron microscopy (SEM). All of the unmodified and modified Co-Cr surfaces were coated with a matrix of poly(d,l-lactide) (PDLLA) and sirolimus (SRL). The in vitro drug release profile was measured for 70 days. The PLLA-modified Co-Cr showed a biphasic release pattern in the initial burst followed by a slow release. On the other hand, the unmodified Co-Cr showed fast drug release and detachment of the coated polymer layer due to the instability of the polymer layer on Co-Cr surface. In comparison, the PLLA-modified Co-Cr preserved a uniform coating without detachment even after 6 weeks of degradation test. The platelet morphology and low density of platelet adhered on the modified layer and the SRL-in-PDLLA coated Co-Cr surfaces demonstrated that these samples would be blood compatible. Therefore, the introduction of PLLA brush onto Co-Cr surface is proved to dramatically improve the durability of the coating layer, and it is a promising strategy to prevent the coating defects found in DESs.
authors.affiliation: Center for Biomaterials, Korea Institute of Science and Technology, Hwarangno 14-gil 5, Seongbuk-gu, Seoul 136-791, Republic of Korea; Department of Biomedical Engineering, Korea University of Science and Technology, 113 Gwahangno, Yuseong-gu, Daejeon 305-333, Republic of Korea; Chemistry Department, Faculty of Science, Minia University, El-Minia 61519, Egypt.
authors.forename: Tarek M
authors.initials: TM
authors.lastname: Bedair
authors.affiliation: Center for Biomaterials, Korea Institute of Science and Technology, Hwarangno 14-gil 5, Seongbuk-gu, Seoul 136-791, Republic of Korea.
authors.forename: Youngjin
authors.initials: Y
authors.lastname: Cho
authors.affiliation: Center for Biomaterials, Korea Institute of Science and Technology, Hwarangno 14-gil 5, Seongbuk-gu, Seoul 136-791, Republic of Korea; Department of Biomedical Engineering, Korea University of Science and Technology, 113 Gwahangno, Yuseong-gu, Daejeon 305-333, Republic of Korea.
authors.forename: Yoon Ki
authors.initials: YK
authors.lastname: Joung
authors.affiliation: Center for Biomaterials, Korea Institute of Science and Technology, Hwarangno 14-gil 5, Seongbuk-gu, Seoul 136-791, Republic of Korea; Department of Biomedical Engineering, Korea University of Science and Technology, 113 Gwahangno, Yuseong-gu, Daejeon 305-333, Republic of Korea. Electronic address: dkh@kist.re.kr.
authors.forename: Dong Keun
authors.initials: DK
authors.lastname: Han
mesh_terms: D001672:Biocompatible Materials; D001792:Blood Platelets / Q000166:cytology; D002448:Cell Adhesion; D008670:Metals / Q000737:chemistry*; D011108:Polymers / Q000737:chemistry*; D013499:Surface Properties
chemical_list: D001672:Biocompatible Materials; D008670:Metals; D011108:Polymers
keywords: Atom transfer radical polymerization; Drug release; Drug-eluting stent; Poly(l-lactide) brush; Ring opening polymerization