title: Spatially discrete thermal drawing of biodegradable microneedles for vascular drug delivery.
abstract: Spatially discrete thermal drawing is introduced as a novel method for the fabrication of biodegradable microneedles with ultra-sharp tip ends. This method provides the enhanced control of microneedle shapes by spatially controlling the temperature of drawn polymer as well as drawing steps and speeds. Particular focus is given on the formation of sharp tip ends of microneedles at the end of thermal drawing. Previous works relied on the fracture of polymer neck by fast drawing that often causes uncontrolled shapes of microneedle tips. Instead, this approach utilizes the surface energy of heated polymer to form ultra-sharp tip ends. We have investigated the effect of such temperature control, drawing speed, and drawing steps in thermal drawing process on the final shape of microneedles using biodegradable polymers. XRD analysis was performed to analyze the effect of thermal cycle on the biodegradable polymer. Load-displacement measurement also showed the dependency of mechanical strengths of microneedles on the microneedle shapes. Ex vivo vascular tissue insertion and drug delivery demonstrated microneedle insertion to tunica media layer of canine aorta and drug distribution in the tissue layer.
authors.affiliation: School of Mechanical Engineering, Yonsei University, Seoul, Republic of Korea.
authors.forename: Chang Kuk
authors.initials: CK
authors.lastname: Choi
authors.affiliation: School of Mechanical Engineering, Yonsei University, Seoul, Republic of Korea.
authors.forename: Kang Ju
authors.initials: KJ
authors.lastname: Lee
authors.affiliation: Division of Cardiovascular Surgery, School of Medicine, Yonsei University, Seoul, Republic of Korea.
authors.forename: Young Nam
authors.initials: YN
authors.lastname: Youn
authors.affiliation: Division of Cardiovascular Surgery, School of Medicine, Yonsei University, Seoul, Republic of Korea.
authors.forename: Eui Hwa
authors.initials: EH
authors.lastname: Jang
authors.affiliation: School of Mechanical Engineering, Yonsei University, Seoul, Republic of Korea.
authors.forename: Woong
authors.initials: W
authors.lastname: Kim
authors.affiliation: School of Mechanical Engineering, Yonsei University, Seoul, Republic of Korea.
authors.forename: Byung-Kwon
authors.initials: BK
authors.lastname: Min
authors.affiliation: School of Mechanical Engineering, Yonsei University, Seoul, Republic of Korea. Electronic address: whryu@yonsei.ac.kr.
authors.forename: WonHyoung
authors.initials: W
authors.lastname: Ryu
mesh_terms: D000818:Animals; D001011:Aorta / Q000187:drug effects; D004285:Dogs; D016503:Drug Delivery Systems / Q000295:instrumentation* / Q000379:methods; D008845:Microinjections / Q000295:instrumentation* / Q000379:methods; D009339:Needles; D011108:Polymers / Q000008:administration & dosage; D013696:Temperature
chemical_list: D011108:Polymers