title: Biodegradable vascular stents with high tensile and compressive strength: a novel strategy for applying monofilaments via solid-state drawing and shaped-annealing processes.
abstract: Monofilaments such as those consisting of polyamide (PA), polydioxanone (PDS), and poly(vinylidene fluoride) (PVDF), have been commonly used in various industries. However, most are non-biodegradable, which is unfavorable for many biomedical applications. Although biodegradable polymers offer significant benefits, they are still limited by their weak mechanical properties, which is an obstacle for use as a biomaterial that requires high strength. To overcome the current limitations of biodegradable monofilaments, a novel solid-state drawing (SSD) process was designed to significantly improve the mechanical properties of both PA and poly(l-lactic acid) (PLLA) monofilaments in this study. Both PA and PLLA monofilaments exhibited more than two-fold increased tensile strength and a highly reduced thickness using SSD. In X-ray diffraction and scanning electron microscopy analyses, it was determined that SSD could not only promote the α-crystal phase, but also smoothen the surface of PLLA monofilaments. To apply SSD-monofilaments with superior properties to cardiovascular stents, a shaped-annealing (SA) process was designed as the follow-up process after SSD. Using this process, three types of vascular stents could be fabricated, composed of SSD-monofilaments: double-helix, single-spring and double-spring shaped stents. The annealing temperature was optimized at 80 °C to minimize the loss of mechanical and physical properties of SSD-monofilaments for secondary processing. All three types of vascular stents were tested according to ISO 25539-2. Consequently, it was confirmed that spring-shaped stents had good recovery rate values and a high compressive modulus. In conclusion, this study showed significantly improved mechanical properties of both tensile and compressive strength simultaneously and extended the potential for biomedical applications of monofilaments.
authors.affiliation: KU-KIST Graduate School of Converging Science and Technology, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul, 02841, Korea. soohkim@kist.re.kr and Center for Biomaterials, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea.
authors.forename: Seung Hyuk
authors.identifier: http://orcid.org/0000-0002-5255-6903
authors.initials: SH
authors.lastname: Im
authors.affiliation: KU-KIST Graduate School of Converging Science and Technology, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul, 02841, Korea. soohkim@kist.re.kr and Center for Biomaterials, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea.
authors.forename: Chang Yong
authors.initials: CY
authors.lastname: Kim
authors.affiliation: Center for Biomaterials, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea and Korea University of Science and Technology, 217 Gajeong-ro, Yuseong-gu, Daejeon 34113, Korea.
authors.forename: Youngmee
authors.initials: Y
authors.lastname: Jung
authors.affiliation: Severance Cardiovascular Hospital, Yonsei University College of Medicine, Seoul, Korea.
authors.forename: Yangsoo
authors.initials: Y
authors.lastname: Jang
authors.affiliation: KU-KIST Graduate School of Converging Science and Technology, Korea University, 145 Anam-ro, Seongbuk-gu, Seoul, 02841, Korea. soohkim@kist.re.kr and Center for Biomaterials, Korea Institute of Science and Technology (KIST), Seoul 02792, Korea and Korea University of Science and Technology, 217 Gajeong-ro, Yuseong-gu, Daejeon 34113, Korea.
authors.forename: Soo Hyun
authors.identifier: http://orcid.org/0000-0002-8391-3686
authors.initials: SH
authors.lastname: Kim
mesh_terms: D001672:Biocompatible Materials / Q000009:adverse effects / Q000737:chemistry*; D019245:Compressive Strength; D006461:Hemolysis; D061307:Human Umbilical Vein Endothelial Cells; D006801:Humans; D008422:Materials Testing; D009757:Nylons / Q000009:adverse effects / Q000737:chemistry*; D011091:Polyesters / Q000009:adverse effects / Q000737:chemistry*; D011474:Prosthesis Design; D015607:Stents / Q000009:adverse effects; D013718:Tensile Strength
chemical_list: D001672:Biocompatible Materials; D009757:Nylons; D011091:Polyesters; C033616:poly(lactide)