Integrin-Specific Mechanoresponses to Compression and Extension Probed by Cylindrical Flat-Ended AFM Tips in Lung Cells

Cells from lung and other tissues are subjected to forces of opposing directions that are largely transmitted through integrin-mediated adhesions. How cells respond to force bidirectionality remains ill defined. To address this question, we nanofabricated flat-ended cylindrical Atomic Force Microscopy (AFM) tips with ~1 µm2 cross-section area. Tips were uncoated or coated with either integrin-specific (RGD) or non-specific (RGE/BSA) molecules, brought into contact with lung epithelial cells or fibroblasts for 30 s to form focal adhesion precursors, and used to probe cell resistance to deformation in compression and extension. We found that cell resistance to compression was globally higher than to extension regardless of the tip coating. In contrast, both tip-cell adhesion strength and resistance to compression and extension were the highest when probed at integrin-specific adhesions. These integrin-specific mechanoresponses required an intact actin cytoskeleton, and were dependent on tyrosine phosphatases and Ca2+ signaling. Cell asymmetric mechanoresponse to compression and extension remained after 5 minutes of tip-cell adhesion, revealing that asymmetric resistance to force directionality is an intrinsic property of lung cells, as in most soft tissues. Our findings provide new insights on how lung cells probe the mechanochemical properties of the microenvironment, an important process for migration, repair and tissue homeostasis.

Disseny i implementació d'una etapa d'acondicionament per a mesures de conductivitat realitzades amb un microscopi de forces atòmiques

En aquest treball, s’ha dissenyat un mòdul d’acondicionament a fi de millorar les mesures de conductivitat realitzades amb un AFM (Microscopi de Forces Atòmiques). L’equip actual disposa d’un preamplificador de baix soroll amb un guany de 10 10V/A. Donat que els corrents que es pretenen mesurar són extremadament petits (~pA), s’ha dissenyat un filtre per eliminar diferents fonts de soroll, com ara el soroll que introdueix la xarxa elèctrica a 50Hz. Es pretén reduir aquesta component freqüencial un factor mínim de 10 (20dB). També s’ha afegit un filtre passa baixos per eliminar els soroll que es troba fora de l’amplada de banda del preamplificador. S’ha introduït una etapa d’amplificació de guany variable: 1, 10 i 100 per augmentar la flexibilitat de l’equip i finalment també s’ha dissenyat una etapa per eliminar la tensió d’offset d’aquest amplificador. L’abast del treball anirà des del disseny fins la implementació final sobre una placa PCB.

Dipòsit i caracterització de capes primes orgàniques de P3HT:PCBM per a aplicacions fotovoltaiques

En un món on el ritme de la societat actual ens ha portat a considerar les energies enovables com a prioritat vital i necessària i en el que es preveu que la demanda energètica augmenti un 50% fins al 2030, l'interès en la recerca de materials emiconductors orgànics per aplicacions de captura solar, ha assolit un potencial enorme de cara al futur. Molts són el avantatges que presenten aquest tipus de materials en front als seus homòlegs inorgànics. La facilitat de fabricació, la utilització de materials més econòmics i amb menys impacte ambiental, així com la possibilitat de produir dispositius flexibles, són algunes de les atractives aracterístiques que presenten aquests materials. No obstant, certs inconvenients om les baixes eficiències energètiques dels dispositius, i la inestabilitat ambiental ue es tradueix en un temps de vida molt reduït, fan que encara s'hagi d'invertir sforç per aconseguir que aquests materials puguin ser utilitzats en el camp de la aptura d'energia solar. El material més prometedor fins a data d'avui és el P3HT:PCBM. Es tracta d'un sistema polímer:molècula lleugera, on el P3HT actua com a component donador del sistema i el PCBM actua com a component acceptor. Les propietats optoelectròniques i eficiències energètiques de combinats orgànics P3HT:PCBM epèn en gran mesura de la seva morfologia i microestructura. Paràmetres com la proporció entre els components, el dissolvent utilitzat en la dissolució, així com 'aplicació de determinats tractaments tèrmics afecten de forma crítica a la seva orfologia. Durant el present treball s'han utilitzat diverses tècniques de caracterització per a estudiar determinades propietats que presenten aquest tipus de aterials. Entre les tècniques experimentals utilitzades hi trobem la microscòpia FM, l'espectroscòpia Raman i la conductimetria AFM o current sensing AFM CS-AFM). Els experiments en temps real durant l'escalfament de capes primes 3HT:PCBM, mostren que el P3HT pateix una cristal·lització al voltant dels 140ºC, permetent el reordenament de les molècules i un millor solapament del sorbitals [pi]-[pi]*, que resulta en un increment del transport de forats a través de la fase donadora del material. Paralel·lament, entre els 80-120ºC, el material també presenta determinats canvis tant en el comportament dels enllaços, com en la cristal·linitat del material, provocant una quasi transició de fase que atribuïm a la transició vitrea del material. Per altra banda, experiments amb conductimetria AFM realitzats en sistemes P3HT:HDPE mostren un signicatiu augment en la eva estabilitat ambiental, que es tradueix en un augment del temps de vida, sense una pèrdua considerable en els seus valors de conducció. Tot i la combinació del P3HT amb proporcions de polímers aïllants de fins al 80%, el sistema és capaç de no perdre la capacitat de transport gràcies a la formació de fases i dominis rics en P3HT. El present treball posa de manifest que ens trobem davant d'una tecnologia emergent i que nous estudis i esforços en la recerca d'aquest tipus materials és fonamental per aconseguir nous resultats i posicionar als materials semiconductors orgànics com una alternativa viable en el camp dels dispositus fotovoltaics. Assumint dades procedents de la tecnologia actual utilitzada en aquest tipus de materials, estudis i avaluacions ambientals i econòmiques mostren que petits increments tant en les eficiències com en el temps de vida de dispositius basats en aterials orgànics, posicionarien a aquest material com a alternativa totalment viable en el mercat fotovoltaic d'un futur proper.

Inducció local de magnetisme mitjançant irradiació d'ions a través de màscares

Degut a la gran demanda tecnològica, actualment hi ha un gran interès en desenvolupar medis magnètics amb entitats ferromagnètiques de dimensions nanomètriques. Aquesta demanda promou la investigació i el desenvolupament de nous materials i processos de fabricació que permetin controlar d’una manera més precisa les propietats magnètiques i estructurals. Entre els mètodes de litografia convencionals (per exemple deposició física a través de màscares, deposició química en fase vapor i electrodeposició), recentment s’ha demostrat que la irradiació amb ions a través de màscares pre‐litografiades, sembla ser un bon mètode per a la fabricació d’estructures ferromagnètiques de l’ordre dels nanòmetres. Aquesta tècnica pot ser aplicada per aprofitar la transició paramagnètica‐ferromagnètica que presenten alguns materials al ser desordenats estructuralment (per exemple FeAl, FePt3, Ni3Sn2). En el treball que es presenta a continuació s’utilitza l’aliatge Fe60Al40 per a fabricar estructures ferromagnètiques embegudes en una matriu paramagnètica mitjançant irradiació amb ions d’argó a través d’una membrana de polimetil metacrilat (PMMA) prèviament litografiada amb feixos d’electrons (EBL). La fabricació d’aquest sistema té com a objectiu d’estudiar l’evolució de la morfologia i el gruix de PMMA (a partir de SEM i AFM) i del comportament magnètic de les estructures fabricades (MFM i MOKE), quan és irradiat consecutivament a diferents energies. Per a completar l’estudi s’han utilitzat simulacions per a determinar les condicions d’irradiació (TRIM), com per a una millor comprensió dels resultats (simulacions micromagnètiques). El contingut de la memòria inclou una breu introducció històrica i conceptual sobre el magnetisme. A continuació s’exposen les tècniques necessàries per a la fabricació, preparació i caracterització de la mostra. Finalment es presenta una discussió dels resultats obtinguts i les conclusions.

Conduction mechanisms and charge storage in Si-nanocrystals metal-oxide-semiconductor memory devices studied with conducting atomic force microscopy

In this work, we demonstrate that conductive atomic force microscopy (C-AFM) is a very powerful tool to investigate, at the nanoscale, metal-oxide-semiconductor structures with silicon nanocrystals (Si-nc) embedded in the gate oxide as memory devices. The high lateral resolution of this technique allows us to study extremely small areas ( ~ 300nm2) and, therefore, the electrical properties of a reduced number of Si-nc. C-AFM experiments have demonstrated that Si-nc enhance the gate oxide electrical conduction due to trap-assisted tunneling. On the other hand, Si-nc can act as trapping centers. The amount of charge stored in Si-nc has been estimated through the change induced in the barrier height measured from the I-V characteristics. The results show that only ~ 20% of the Si-nc are charged, demonstrating that the electrical behavior at the nanoscale is consistent with the macroscopic characterization.

Modificacion de las propiedades opticas y mecanicas de polimeros mediante implantacion ionica

En el presente trabajo se estudian los efectos introducidos por la implantación de Nitrógeno atómico y Silicio sobre probetas de policarbonato empleadas para usos ópticos. Distintas dosis de Nitrógeno y Silicio fueron implantadas de cara a poner de manifiesto el efecto de la dosis sobre las propiedades ópticas y mecánicas. Se llevaron a cabo ensayos mecánicos de microdureza, nanodureza, y AFM, así como ensayos ópticos de Reflexión-absorción IR y Transmitancia UV-VIS. Los resultados muestran un endurecimiento superficial para las implantaciones a dosis altas de Nitrógeno, así como cambios considerables en los espectros de transmitancia.

Graphoepitaxy of CeO2 on MgO and its application to the fabrication of 45° grain boundary Josephson junctions of YBa2Cu3O7-x

We communicate a detailed study of the epitaxial growth of CeO2 on MgO. The key feature of the growth is the dependence of the in¿plane orientation of the CeO2 epitaxial layer on the MgO surface morphology. Atomic force microscopic (AFM) measurements, x¿ray analyses, as well as high¿resolution transmission electron microscopy (HRTEM) investigations reveal that on rough substrates a cube¿on¿cube growth of CeO2 on MgO occurs while on smooth substrates the CeO2 unit cell is rotated around the surface normal by 45° with respect to the MgO unit cell when the deposition rate is low (~0.3 Å/s) during the first stages of growth. This growth mechanism can be used for a defined fabrication of 45° grain boundaries in the CeO2 layer by controlling the surface roughness of the MgO substrate. This report demonstrates that these 45° grain boundaries may be used to fabricate YBa2Cu3O7¿x Josephson junctions.

Photonic characteristics of Langmuir-Blodgett self-assembled monolayers of colloidal silica particles

Monodispersed colloidal crystals based on silica sub-micrometric particles were synthesized using the Stöber-Fink-Bohn process. The control of nucleation and coalescence result in improved characteristics such as high sphericity and very low size dispersion. The resulting silica particles show characteristics suitable for self-assembling across large areas of closely-packed 2D crystal monolayers by an accurate Langmuir-Blodgett deposition process on glass, fused silica and silicon substrates. Due to their special optical properties, colloidal films have potential applications in fields including photonics, electronics, electro-optics, medicine (detectors and sensors), membrane filters and surface devices. The deposited monolayers of silica particles were characterized by means of FESEM, AFM and optical transmittance measurements in order to analyze their specific properties and characteristics. We propose a theoretical calculation for the photonic band gaps in 2D systems using an extrapolation of the photonic behavior of the crystal from 3D to 2D. In this work we show that the methodology used and the conditions in self-assembly processes are decisive for producing high-quality two-dimensional colloidal crystals by the Langmuir-Blodgett technique.

Complexes of Pd(II) and Pt(II) with 9-aminoacridine: reactions with DNA and study of their antiproliferative activity

Four new metal complexes {M = Pd(II) or Pt(II)} containing the ligand 9-aminoacridine (9AA) were prepared. The compounds were characterized by FT-IR and 1H, 13C, and 195Pt NMR spectroscopies. Crystal structure of the palladium complex of formulae [Pd(9AA)(μ-Cl)]2 · 2DMF was determined by X-ray diffraction. Two 9-acridine molecules in the imine form bind symmetrically to the metal ions in a bidentate fashion through the imine nitrogen atom and the C(1) atom of the aminoacridine closing a new five-membered ring. By reaction with phosphine or pyridine, the Cl bridges broke and compounds with general formulae [Pd(9AA)Cl(L)] (where L = PPh3 or py) were formed. A mononuclear complex of platinum of formulae [Pt(9AA)Cl(DMSO)] was also obtained by direct reaction of 9-aminoacridine and the complex [PtCl2(DMSO)2]. The capacity of the compounds to modify the secondary and tertiary structures of DNA was evaluated by means of circular dichroism and electrophoretic mobility. Both palladium and platinum compounds proved active in the modification of both the secondary and tertiary DNA structures. AFM images showed noticeable modifications of the morphology of the plasmid pBR322 DNA by the compounds probably due to the intercalation of the complexes between base pairs of the DNA molecule. Finally, the palladium complex was tested for antiproliferative activity against three different human tumor cell lines. The results suggest that the palladium complex of formula [Pd(9AA)(μ-Cl)]2 has significant antiproliferative activity, although it is less active than cisplatin.

Complexes of Pd(II) and Pt(II) with 9-aminoacridine: reactions with DNA and study of their antiproliferative activity

Four new metal complexes {M = Pd(II) or Pt(II)} containing the ligand 9-aminoacridine (9AA) were prepared. The compounds were characterized by FT-IR and 1H, 13C, and 195Pt NMR spectroscopies. Crystal structure of the palladium complex of formulae [Pd(9AA)(μ-Cl)]2 · 2DMF was determined by X-ray diffraction. Two 9-acridine molecules in the imine form bind symmetrically to the metal ions in a bidentate fashion through the imine nitrogen atom and the C(1) atom of the aminoacridine closing a new five-membered ring. By reaction with phosphine or pyridine, the Cl bridges broke and compounds with general formulae [Pd(9AA)Cl(L)] (where L = PPh3 or py) were formed. A mononuclear complex of platinum of formulae [Pt(9AA)Cl(DMSO)] was also obtained by direct reaction of 9-aminoacridine and the complex [PtCl2(DMSO)2]. The capacity of the compounds to modify the secondary and tertiary structures of DNA was evaluated by means of circular dichroism and electrophoretic mobility. Both palladium and platinum compounds proved active in the modification of both the secondary and tertiary DNA structures. AFM images showed noticeable modifications of the morphology of the plasmid pBR322 DNA by the compounds probably due to the intercalation of the complexes between base pairs of the DNA molecule. Finally, the palladium complex was tested for antiproliferative activity against three different human tumor cell lines. The results suggest that the palladium complex of formula [Pd(9AA)(μ-Cl)]2 has significant antiproliferative activity, although it is less active than cisplatin.

Complexes of Pd(II) and Pt(II) with 9-aminoacridine: reactions with DNA and study of their antiproliferative activity

Four new metal complexes {M = Pd(II) or Pt(II)} containing the ligand 9-aminoacridine (9AA) were prepared. The compounds were characterized by FT-IR and 1H, 13C, and 195Pt NMR spectroscopies. Crystal structure of the palladium complex of formulae [Pd(9AA)(μ-Cl)]2 · 2DMF was determined by X-ray diffraction. Two 9-acridine molecules in the imine form bind symmetrically to the metal ions in a bidentate fashion through the imine nitrogen atom and the C(1) atom of the aminoacridine closing a new five-membered ring. By reaction with phosphine or pyridine, the Cl bridges broke and compounds with general formulae [Pd(9AA)Cl(L)] (where L = PPh3 or py) were formed. A mononuclear complex of platinum of formulae [Pt(9AA)Cl(DMSO)] was also obtained by direct reaction of 9-aminoacridine and the complex [PtCl2(DMSO)2]. The capacity of the compounds to modify the secondary and tertiary structures of DNA was evaluated by means of circular dichroism and electrophoretic mobility. Both palladium and platinum compounds proved active in the modification of both the secondary and tertiary DNA structures. AFM images showed noticeable modifications of the morphology of the plasmid pBR322 DNA by the compounds probably due to the intercalation of the complexes between base pairs of the DNA molecule. Finally, the palladium complex was tested for antiproliferative activity against three different human tumor cell lines. The results suggest that the palladium complex of formula [Pd(9AA)(μ-Cl)]2 has significant antiproliferative activity, although it is less active than cisplatin.

Anisotropic surface properties of micro/nanostructured a-C:H:F thin films with self-assembly applications

The singular properties of hydrogenated amorphous carbon (a-C:H) thin filmsdeposited by pulsed DC plasma enhanced chemical vapor deposition (PECVD), such as hardness and wear resistance, make it suitable as protective coating with low surface energy for self-assembly applications. In this paper, we designed fluorine-containing a-C:H (a-C:H:F) nanostructured surfaces and we characterized them for self-assembly applications. Sub-micron patterns were generated on silicon through laser lithography while contact angle measurements, nanotribometer, atomic force microscopy (AFM), and scanning electron microscopy (SEM) were used to characterize the surface. a-C:H:F properties on lithographied surfaces such as hydrophobicity and friction were improved with the proper relative quantity of CH4 and CHF3 during deposition, resulting in ultrahydrophobic samples and low friction coefficients. Furthermore, these properties were enhanced along the direction of the lithographypatterns (in-plane anisotropy). Finally, self-assembly properties were tested with silicananoparticles, which were successfully assembled in linear arrays following the generated patterns. Among the main applications, these surfaces could be suitable as particle filter selector and cell colony substrate.