Minispheroids as a Tool for Ligament Tissue Engineering: Do the Self-Assembly Techniques and Spheroid Dimensions Influence the Cruciate Ligamentocyte Phenotype?

Spheroid culture might stabilize the ligamentocyte phenotype. Therefore, the phenotype of lapine cruciate ligamentocyte (L-CLs) minispheroids prepared either by hanging drop (HD) method or by using a novel spheroid plate (SP) and the option of methyl cellulose (MC) for tuning spheroid formation was tested. A total of 250 and 1000 L-CLs per spheroid were seeded as HDs or on an SP before performing cell viability assay, morphometry, gene expression (qRT-PCR) and protein immunolocalization after 7 (HD/SP) and 14 (SP) days. Stable and viable spheroids of both sizes could be produced with both methods, but more rapidly with SP. MC accelerated the formation of round spheroids (HD). Their circular areas decreased significantly during culturing. After 7 days, the diameters of HD-derived spheroids were significantly larger compared to those harvested from the SP, with a tendency of lower circularity suggesting an ellipsoid shape. Gene expression of decorin increased significantly after 7 days (HD, similar trend in SP), tenascin C tended to increase after 7 (HD/SP) and 14 days (SP), whereas collagen type 1 decreased (HD/SP) compared to the monolayer control. The cruciate ligament extracellular matrix components could be localized in all mini-spheroids, confirming their conserved expression profile and their suitability for ligament tissue engineering.     

Inversion of quartz solid solutions at cryogenic temperatures

Quartz solid solution crystals of six different compositions were obtained from crystallization of glass powders belonging to the Li₂O–Al₂O₃-SiO₂ (LAS) system. They were analyzed in situ by laboratory-based X-ray diffraction down to cryogenic temperatures (−190°C). Temperature-resolved analysis of their lattice parameters allowed determination of the critical inversion temperature T_c in these materials, marking the displacive phase transition from a high-quartz- to a low-quartz-like lattice. Integrating available data from other literature sources, an updated phase diagram for the occurrence of high and low quartz solid solution phases is provided for the LAS system; these data are expected to support future development of functional materials relying on these crystalline phases.     

Plasmabromierung von graphitischen Materialien

Plasma bromination of graphitic materials The high‐yield and high‐selective plasma chemical bromination of polyolefin surfaces was transferred to graphitic materials. Graphene‐like surfaces of highly‐oriented pyrolytic graphite (HOPG), natural graphite, multi‐walled carbon nanotubes(MWCNT) and carbon fibres were exposed to bromine plasma. This bromination proceeds at polyolefin surfaces as radical substitution by hydrogen abstraction and bromine attachment or as nucleophilic substitution. However, bromination of graphitic structures picks up sp³ carbon atoms occurring as structural defects or more probably proceeds as electrophilic addition onto the substituted aromatic double bonds. In this process the planar sp² carbon‐carbon bonds are transferred to the tetrahedral sp³ C‐C bonds with non‐conducting structure. Using the bromine plasma maximal bromination yields varied, were dependent on the type of carbon material and ranged from 10–50% Br/C. Using bromoform as Br‐precursor and accepting layer deposition about 70% Br/C were found. Subsequently, different amines were grafted wet‐ or gas phase chemically by nucleophilic substitution. The grafting yields amounted 1–10 molecules per 100 carbon atoms, which was lower than for grafting yields on brominated polyolefin surfaces ranging between 1–22 molecules per 100 carbon atoms. After grafting more or less all non‐grafted Br‐atoms were also diminished, that indicated a partial reconstruction of the planar sp² graphitic structure.     

Spray-Dried TiO2(B)-Containing Photocatalytic Glass-Ceramic Nanobeads

Glass-ceramic nanospheres of molar composition 0.83 SiO₂ · 0.17 TiO₂ are produced by the sol-gel spray-drying method followed by controlled heat treatments up to 1200 ° C. TiO₂(B) and anatase nanocrystals are precipitated in the glassy matrix: the latter phase gradually predominates with increasing ceramization temperature and time, in parallel to an overall increase in crystal sizes. The nanospheres exhibit evident photocatalytic activity under UV-A irradiation, especially at annealing stages involving a comparatively higher amount of TiO₂(B) and smaller crystals. The occurrence of TiO₂(B) in this simplified binary glass-ceramic material underlines the key role of this phase in the dynamics of crystallizing TiO₂-bearing silicate melts.     

Elektrospray‐Ionisation (ESI)

EElectrospray‐ionization (ESI) – pinhole‐free electrophoretic deposition of ultra thin polymer layers Electrospray ionization (ESI) of polymer solutions is used in mass spectroscopy to analyze the molar mass of macromolecules. The singularized polymer molecules are transferred into the mass spectrometer after separating through a special mechanism under high voltage and normal pressure conditions. This process can be adapted for plane deposition of single polymer molecules. Structure, composition and molar mass distribution of polymers are retained. Layers of polar or ionic polymers can be deposited in a thickness of monolayers up to hundreds of nanometers. It is interesting to mention that the ESI‐process belongs to the electrophoretic techniques. Therefore, deposition of pinhole‐free layers on electrical conductive substrates is not only possible on the nozzle facing side of the substrate but although on the back side. This behavior was used to enwrap closely packed carbon fiber bundles with adhesive polymer layers.     

Insight in the outside: New applications of low-energy ion scattering

Low energy ion scattering is used to selectively probe the outermost atomic layer of the surface. The development of double toroidal analyzers has improved the detection sensitivity of low energy ion scattering by orders of magnitude. The features of these analyzers are discussed. It is shown that the absence of matrix effects makes it possible to quantify the surface density of fluorine in polymers with a LiF(1 0 0) surface. The extreme surface sensitivity of LEIS also enables one to study intramolecular segregation processes. As an example the aging of a polypropylene surface that has been activated with atomic oxygen is described. As an example of the LEIS analysis of highly dispersed isolating surfaces, the formation of coke on a commercial three-way catalyst is discussed.     

Electrospray ionization for deposition of ultra-thin polymer layers – principle,electrophoretic effect and applications

Nebulizing of polymer solutions, in a high-voltage field under atmospheric conditions by electrospray ionization (ESI), is a comfortable way to deposit ultra-thin layers of polar or ionic polymers onto any conductive substrate materials. The substrate is grounded and the polymer solution is sprayed through a powered capillary. The formed charged droplets shrink by solvent evaporation during their way to the grounded substrate, the charges close ranks and the droplets collapse consecutively by charge repulsion, thus forming finally charged single macromolecules. After their discharging at the grounded substrate, an ultra-thin ‘quasi-monomolecular’ polymer layer is formed. It could be shown by imaging of scratches through the polymer layer by atomic force microscopy that the deposited polymer layers are dense at a thickness of about 10?nm. Carbon fibre bundles were coated with poly(allylamine) (PAAm) or poly(acrylic acid) (PAA) as potential adhesion-promoting layers in fibre–polymer composites. The polymer deposition is self-inhibiting after formation of a continuous coverage of about 200?nm for PAAm and 30?nm for PAA as result of surface charging. Continuous deposition onto such isolating layers or polymers without charging can be achieved by using current of alternating polarity. The film formation is self-healing because of the electrophoretic effect, i.e. the ion discharging occurs preferentially at non-coated areas. This electrophoretic effect of ESI was demonstrated by completely enwrapping all the carbon fibres of the roving within a distance of about 100?μm far from its outside and also at the backside of the fibre bundle with about 80% of the topside coverage, as measured by X-ray photoelectron spectroscopy and visualized using scanning electron microscopy.     

ATP-independent contractile proteins from plants

Emerging technologies are creating increasing interest in smart materials that may serve as actuators in micro- and nanodevices. Mechanically active polymers currently studied include a variety of materials. ATP-driven motor proteins, the actuators of living cells, possess promising characteristics, but their dependence on strictly defined chemical environments can be disadvantagous. Natural proteins that deform reversibly by entropic mechanisms might serve as models for artificial contractile polypeptides with useful functionality, but they are rare. Protein bodies from sieve elements of higher plants provide a novel example. sieve elements form microfluidics systems for pressure-driven transport of photo-assimilates throughout the plant. Unique protein bodies in the sieve elements of legumes act as cellular stopcocks, by undergoing a Ca2+-dependent conformational switch in which they plug the sieve element. In living cells, this reaction is probably controlled by Ca2+-transporters in the cell membrane. Here we report the rapid, reversible, anisotropic and ATP-independent contractility in these protein bodies in vitro. Considering the unique biological function of the legume 'crystalloid' protein bodies and their contractile properties, we suggest to give them the distinctive name forisome ('gate-body'; from the Latin foris, the wing of a gate).