Suchergebnisse

Melt blends of chitosan and biodegradable aliphatic polyester have been physically and biologically studied, presenting great potential for biomedical applications. Structurally, poly(butylene succinate)–chitosan (PBS/Cht) composite scaffolds are covered by a thin PBS layer, preventing the desired interaction of cells/tissues with the chitosan particules. In the present work, a selective and controlled ablation of this skin layer was induced by UV laser processing. X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF–SIMS) data demonstrated an increment of chitosan components and others resulting from the laser ablation process. The biological activity (i.e. cell viability and proliferation) on the inner regions of the composite scaffolds is not significantly different from those of the external layer, despite the observed differences in surface roughness (determined by interferometric optical profilometry) and wettability (water contact angle). However, the morphology of human osteoblastic cells was found to be considerably different in the case of laser-processed samples, since the cells tend to aggregate in multilayer columnar structures, preferring the PBS surface and avoiding the chitosan-rich areas. Thus, UV laser ablation can be considered a model technique for the physical surface modification of biomaterials without detrimental effects on cellular activity. ; This work was partially supported by the European Union Integrated Project GENOSTEM (LSH-STREP-CT-2003-503161), the European Union Network of Excellence EXPERTISSUES (NMP3-CT-2004-500283), the Interreg III Project PROTEUS (SP1P151/03) and Xunta de Galicia (Consolidacion 2006/12). The Portuguese Foundation for Science and Technology is also acknowledged for a PhD grant to A.M. (SFRH/BD/24382/2005). The authors wish to thank C. Serra from CACTI of the University of Vigo for the XPS and ToF-SIMS ...

10 pags., 7 figs., 2 tabs. ; In this work, we prepare and characterize multiphasic thin films containing poly(ε-caprolactone), PCL, poly(butylene succinate), PBS, and a poly (butylene succinate-ran-ϵ-caprolactone) (PBS-ran-PCL) random copolyester. To that aim, thin films were prepared by sequential dipping of a silicon substrate into chloroform solutions of the respective polymers. The preparation method resulted in films with varying compositions of PCL and PBS components depending on the initial concentration of the dipping solutions and the number of dipping steps employed for the preparation of the samples. Atomic force microscopy (AFM), grazing incidence X-ray scattering at wide angle (GIWAXS) and scattering-type scanning near-field optical microscopy (s-SNOM) and Fourier transform infrared nanospectroscopy (nano-FTIR) were employed to characterize the films obtained. As chloroform can dissolve all components, the final composition of the film was always rich in the last deposited layer component. The thin films obtained were semicrystalline with a complex axialitic or dendritic morphology of the dominant component (that one deposited last) with traces of the other components, whose presence and location was revealed by s-SNOM/nano-FTIR. ; This study was supported by Spanish Ministry of Science, Innovation and Universities (MAT2017- 83014-C2-1-P, MAT2017-83014-C2-2-P, PID2019-107514 GB-I00/AEI/ 10.13039/501100011033 and PID2019-106125 GB-I00/AEI/ 10.13039/501100011033). We also acknowledge funding by Basque Government through grant IT1309-19. The authors acknowledge beamtime access at ALBA BL11 via proposal 2018072905 and the assistance of JC Martinez during the measurements. We would also like to thank the financial support provided by the BIODEST project; this project has received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 778092. CO wants to acknowledge "Diputaci on Foral de Gipuzkoa" in the framework program "Fellows Gipuzkoa de Atracci ́on y Retenci ́on de Talento". RH is member of the Interdisci-plinary Platform for Sustainable Plastics towards a Circular Economy (SusPlast) from the Spanish National Research Council (CSIC).

In this work we present the formation of laser induced periodic surface structures (LIPSS) on spin-coated thin films of several model aromatic polymers including poly(ethylene terephthalate), poly(trimethylene terephthalate) and poly carbonate bis-phenol A upon irradiation with femtosecond pulses of 795 and 265 nm at fluences well below the ablation threshold. LIPSS are formed with period lengths similar to the laser wavelength and parallel to the direction of the laser polarization vector. Formation of LIPSS upon IR irradiation at 795 nm, a wavelength at which the polymers absorb weakly, contrasts with the absence of LIPSS in this spectral range upon irradiation with nanosecond pulses. Real and reciprocal space characterization of LIPSS obtained by Atomic Force Microscopy (AFM) and Grazing Incidence Small Angle X-ray Scattering (GISAXS), respectively, yields well correlated morphological information. Comparison of experimental and simulated GISAXS patterns suggests that LIPSS can be suitably described considering a quasi-one-dimensional paracrystalline lattice and that irradiation parameters have an influence on the order of such a lattice. Fluorescence measurements, after laser irradiation, provide indirect information about dynamics and structure of the polymer at the molecular level. Our results indicate that the LIPSS are formed by interference of the incident and surface scattered waves. As a result of this process, heating of the polymer surface above its glass transition temperature takes place enabling LIPSS formation. © 2013 the Owner Societies. ; Funding from MICINN, Spain (Projects CTQ2010-15680,FIS2009-09522, MAT2012-33517 and CSD2007-00013) and Junta de Castilla y León (Project SA086A12-2). The experiments performed at BW4 in HASYLAB (DESY,Germany) were supported by the European Union (Contract RII3-CT-2004-506008 (IA-SFS).MINECO (previous MICINN), Spain, Ramón y Cajal contract (RYC-2011-08069), FPI fellowship and PTA contract ; Peer Reviewed

7 pags., 6 figs. ; The evolution of the magnetic anisotropy directions has been studied in a magnetite (FeO) thin film grown by infrared pulsed-laser deposition on SrTiO(100):Nb substrate. The magnetic easy axes at room temperature are found along the in-plane 〈100〉 film directions, which means a rotation of the easy axis by 45° with respect to the directions typically reported for bulk magnetite and films grown on single-crystal substrates. Moreover, when undergoing the Verwey transition temperature, T, the easy axis orientation evolves to the 〈110〉 film directions. This anomalous behavior has been demonstrated by measuring first the angular dependence of coercivity and remanence well above and below T by high-resolution vectorial magneto-optical Kerr effect (v-MOKE). Ferromagnetic resonance (FMR) measurements have additionally proven a well-defined fourfold magnetic anisotropy induced during growth with confirmed easy axis directions along 〈100〉 for T > T and 〈110〉 for T < T. These results provide a clear proof of the possibility of tuning magnetic anisotropy in FeO thin films by proper control on the growth parameters and substrate choice. ; This research was supported by the Regional Government of Madrid through NANOMAGCOST project (P2018/NMT-4321) and by the Spanish Ministry of Economy and Competitiveness (MINECO) through Project CTQ2016-75880-P. M. O. thanks CSIC for contract and E. R. thanks MINECO for the tenure of a Ramón y Cajal contract (No. RYC-2011-08069). The work in Lausanne was supported by the Sinergia grant "Mott physics beyond the Heisenberg model" of the Swiss NSF. The work in BUTE (Hungary) was supported by NKFIH Grant No. K119442 and 2017-1.2.1-NKP-2017-00001, and by the BME-Nanotechnology FIKP grant of EMMI (BME FIKP-NAT). IMDEA Nanoscience is supported by the 'Severo Ochoa' Programme for Centres of Excellence in R&D, MINECO [grant number SEV-2016-0686]