title: Temperature-responsive electrospun nanofibers for 'on-off' switchable release of dextran.
abstract: We propose a new type of 'smart' nanofiber (NF) with dynamically and reversibly tunable properties for the 'on-off' controlled release of the polysaccharide dextran. The fibers are produced by electrospinning copolymers ofN-isopropylacrylamide (NIPAAm) andN-hydroxymethylacrylamide (HMAAm). The OH groups of HMAAm are subsequently crosslinked by thermal curing. The copolymers were successfully fabricated into a well-defined nanofibrous structure with a diameter of about 600-700 nm, and the fibers preserved their morphology even after thermal curing. The resulting crosslinked NFs showed rapid and reversible volume changes in aqueous media in response to cycles of temperature alternation. The fibrous morphology was maintained for the crosslinked NFs even after the cycles of temperature alternation, while non-crosslinked NFs collapsed and dispersed quickly in the aqueous solution. Dextran-containing NFs were prepared by electrospinning the copolymers blended with fluorescein isothiocyanate (FITC)-dextran, and the 'on-off' switchable release of FITC-dextran from the crosslinked NFs was observed. Almost all the FITC-dextran was released from the NFs after six heating cycles, whereas only a negligible amount of FITC-dextran was evolved during the cooling process. The reported incorporation of smart properties into NFs takes advantage of their extremely large surface area and porosity and is expected to provide a simple platform for on-off drug delivery.
authors.affiliation: Department of Materials Engineering, Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8577, Japan; Biomaterials Unit, International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki, 305-0044, Japan.
authors.forename: Young-Jin
authors.initials: YJ
authors.lastname: Kim
authors.affiliation: Biomaterials Unit, International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki, 305-0044, Japan.
authors.forename: Mitsuhiro
authors.initials: M
authors.lastname: Ebara
authors.affiliation: Department of Materials Engineering, Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8577, Japan; Biomaterials Unit, International Center for Materials Nanoarchitectonics (WPI-MANA), National Institute for Materials Science (NIMS), 1-1 Namiki, Tsukuba, Ibaraki, 305-0044, Japan.
authors.forename: Takao
authors.initials: T
authors.lastname: Aoyagi
keywords: N-isopropylacrylamide (NIPAAm); drug delivery system; electrospinning; smart nanofiber; thermal crosslinking; thermoresponsive nanofiber