Evaluation of direct light processing for the fabrication of bioactive ceramic scaffolds: Effect of pore/strut size on manufacturability and mechanical performance

Bioactive ceramic scaffolds for bone regeneration consisting of a three-dimensional mesh of interpenetrating struts with square section were fabricated via Digital Light Processing (DLP). The ability of the technique to manufacture 3D porous structures from β-tricalcium phosphate (β-TCP) powders with different dimensions of struts and pores was evaluated, identifying the possibilities and limitations of the manufacturing process. Small pore sizes were found to seriously complicate the elimination of excess slurry from the scaffold’s innermost pores. The effect of the strut/pore size on the mechanical performance of the scaffolds under compressive stresses was also evaluated, but no significant influence was found. Under compressive stresses, the structures resulted weaker when tested perpendicularly to the printing plane due to interlayer shear failure. Interlayer superficial grooves are proposed as potential failure-controlling defects, which could also explain the lack of a Weibull size effect on the mechanical strength of the fabricated DLP scaffolds.     

Recent Biophysical Issues About the Preparation of Solute-Filled Lipid Vesicles

Here we report some recent biophysical issues on the preparation of solute-filled lipid vesicles and their relevance to the construction of “synthetic cells.” First, we introduce the “semi-synthetic minimal cells” as the liposome-based cell-like systems, which contain a minimal number of biomolecules required to display simple and complex biological functions. Next, we focus on recent aspects related to the construction of synthetic cells. Emphasis is given to the interplay between the methods of synthetic cell preparation and the physics of solute encapsulation. We briefly introduce the notion of structural and compositional “diversity” in synthetic cell populations.     

2-Phenyloxazole-4-carboxamide as a Scaffold for Selective Inhibition of Human Monoamine Oxidase B

A series of 2-phenyloxazoles bearing an amide group at position 4 were designed and synthesized for evaluation as potential inhibitors of human recombinant monoamine oxidases (hrMAOs). Results of kinetics experiments demonstrated that all compounds behave as competitive MAO inhibitors, with good selectivity toward the MAO-B isoform. The most potent and selective derivatives are characterized by inhibition constant (K_i) values in the sub-micromolar range and a good selectivity index (K_{i MAO-A}/K_{i MAO-B}>50). Some derivatives were also found to be able to inhibit MAO activity in nerve growth factor (NGF)-differentiated PC12 cells, taken as a model of neuronal cells. In particular, 2-(2-hydroxyphenyl)-N-phenyloxazole-4-carboxamide (compound 4 a ) may be a promising new scaffold, exerting the highest selectivity and inhibitory effect toward MAOs in NGF-differentiated PC12 cell lysates, without compromising cell viability. Molecular docking analysis allowed a rationalization of the experimentally observed binding affinity and selectivity.     

Thermo-physical properties of as deposited and aged thermal barrier coatings (TBC) for gas turbines: State-of-the art and advanced TBCs

In the perspective of fuelling the future generations of gas turbines by hydrogen rich syngas, the evaluation of the effect of a higher water vapour content into the flue gases on the TBC used, or potentially usable, is a need. For this purpose YPSZ APS TBC with two different microstructures have been exposed for 500?h at different temperatures in the range 1000?°C–1250?°C either in air and air +20% vol. H₂O. The comparison between the different testing conditions has been performed in terms of sintering kinetics and phase stability, as evaluated by thermal diffusivity measurements and Synchrotron X-Rays diffraction, respectively. Furthermore the characterisation of thermal properties of two innovative TBCs (GZO-YPSZ and YAG) potentially able to withstand the CMAS attack and erosive environments, respectively, has been carried out.No clear evidence of a different behaviour of TBC has been observed, at least in the considered aging time and temperature range.     

Identification of in vitro phosphorylation sites in the growth cone protein SCG10. Effect Of phosphorylation site mutants on microtubule-destabilizing activity

SCG10 is a neuron-specific, membrane-associated protein that is highly concentrated in growth cones of developing neurons. Previous studies have suggested that it is a regulator of microtubule dynamics and that it may influence microtubule polymerization in growth cones. Here, we demonstrate that in vivo, SCG10 exists in both phosphorylated and unphosphorylated forms. By two-dimensional gel electrophoresis, two phosphoisoforms were detected in neonatal rat brain. Using in vitro phosphorylated recombinant protein, four phosphorylation sites were identified in the SCG10 sequence. Ser-50 and Ser-97 were the target sites for protein kinase A, Ser-62 and Ser-73 for mitogen-activated protein kinase and Ser-73 for cyclin-dependent kinase. We also show that overexpression of SCG10 induces a disruption of the microtubule network in COS-7 cells. By expressing different phosphorylation site mutants, we have dissected the roles of the individual phosphorylation sites in regulating its microtubule-destabilizing activity. We show that nonphosphorylatable mutants have increased activity, whereas mutants in which phosphorylation is mimicked by serine-to-aspartate substitutions have decreased activity. These data suggest that the microtubule-destabilizing activity of SCG10 is regulated by phosphorylation, and that SCG10 may link signal transduction of growth or guidance cues involving serine/threonine protein kinases to alterations of microtubule dynamics in the growth cone.     

Biodegradable hollow microfibres to produce bioactive scaffolds

Biodegradable hollow microfibres containing particles loaded with specific active agents can be potentially employed to produce a special kind of substrate for tissue engineering, able to function as a scaffold and at the same time to act as a drug‐releasing system. Biodegradable hollow microfibres based on poly(lactic acid) were produced by a dry–wet spinning procedure. Drug‐loaded microparticles were prepared by a simple oil‐in‐water emulsion and entrapped inside the fibres. The morphology of both fibres and particles was investigated by scanning electron microscopy. The mechanical and thermal properties of the fibres were investigated by tensile tests and differential scanning calorimetry. In vitro tests were performed to evaluate the release of the drug from the fibres loaded with the particles Copyright © 2004 Society of Chemical Industry     

Inorganic–organic hybrid materials with zirconium oxoclusters as protective coatings on aluminium alloys

Inorganic–organic hybrid materials are attracting a strong scientific interest mainly for their outstanding inherent mechanical and thermal properties, which can be traced back to the intimate coupling of both inorganic and organic components. By carefully choosing the experimental parameters used for their synthesis, chemically and thermally stable acrylate-based hybrid material embedding the zirconium oxocluster Zr₄O₄(OMc)₁₂, where OMcCH₂C(CH₃)C(O)O, can be deposited as UV-cured films on aluminium alloys.

In particular, the molar ratios between the oxocluster and the monomer, the polymerisation time, the amount of photo-initiator and the deposition conditions, by using an home-made spray-coating equipment, were optimised in order to obtain the best performing layers in terms of transparency and hardness to coat aluminium alloy (AA1050, AA6060 and AA2024) sheets. Furthermore, it was also evaluated whether the hybrid coatings behave as barrier to corrosion.

Several coated samples were prepared and characterised. Environmental scanning electronic microscopy (ESEM) and scratch test were used to investigate the morphology of the films and to evaluate their scratch resistance, respectively. Electrochemical impedance spectroscopy (EIS) was performed in order to evaluate if the coatings actually protect the metallic substrate from corrosion.

In order to measure shear storage modulus (G′) and loss modulus (G″) of the materials used for coatings, bulk samples were also obtained by UV-curing of the precursors solution. Dynamical mechanical thermal analysis (DMTA) was performed in shear mode on cured disks of both the hybrid materials and pristine polymer for comparison. The values of T_g were read off as the temperatures of peak of loss modulus. The length and mass of all the samples were measured before and after the DMTA analysis, so that the shrinkage of the materials in that temperature range was exactly evaluated.     

Co- and Ni-exchanged ferrierite: The contribution of synchrotron X-ray diffraction data to siting of TMIs

High-silica zeolites exchanged with transition metal ions (TMIs) are the subject of great interest for their unusual catalytic activity and selectivity. Structural information like coordination and accessibility of TMIs in zeolites are important factors for understanding their catalytic activity. Siting of TMIs in zeolites is typically obtained by spectroscopic (EXAFS, EPR, UV–vis and IR) and computational methods, as in the case of Co-ferrierite. However, some controversy exists in the literature concerning the model for incorporation of bare Co ions in ferrierite. We show here that the results of our synchrotron X-ray powder diffraction studies on Co- and Ni-exchanged ferrierite (Si/Al = 8.5) are in a good agreement with the model of Co siting based on an indirect spectroscopic approach and help to validate this model. By direct structural evidences, a possible explanation for the larger catalytic activity of Co sites in the main channels of ferrierite can be inferred. A combination of data from in situ XRD continuous monitoring of the Co ion migration during calcination and crystal-chemical considerations allows to device a strategy for the design of optimised co-cations containing Co-ferrierite catalysts.     

Conservative surgery for stage I ovarian carcinoma in women of childbearing age

OBJECTIVE: To assess the results of a policy of tailored conservative surgical management for young women with stage I ovarian carcinomas. DESIGN: Retrospective study. PARTICIPANTS: Ninety-nine women aged 40 years or younger who underwent either primary surgery in our department or were referred after primary surgery performed elsewhere. METHODS: Of the 99 women in our study, 56 underwent fertility-sparing surgery and 43 more radical surgery. Minimal requirements for conservative management were adequate staging and complete information about the therapeutic options. Factors important in the choice of the treatment were, age, wish to preserve fertility, histologic type and grade, and the stage of the tumour. RESULTS: Conservative treatment was conducted in 84% of nulliparous and in 33% of parous women; 62% of grade 1 tumours, 48% of grade 2, and 50% of grade 3 were treated conservatively. With a median follow up of seven years, we observed five recurrences (9%) of carcinoma in women treated conservatively and five (12%) in those treated more radically. Two women (one in each treatment arm) were saved after recurrence. Two recurrences after conservative surgery involved the residual ovary (3.6%). Two women developed borderline tumour in the contralateral ovary and both were treated by surgery. CONCLUSION: After adequate staging and accurate information is given to the patient, conservative treatment may be safe in some women with early ovarian cancer. The risk of recurrence in the contralateral ovary is low. Conservative surgery may be also considered in some Stage I grade 3 tumours and in some women with stage JC tumours.     

Dexamethasone inhibition of interferon-alpha 2-induced stimulation of cortisol and growth hormone secretion in chronic myeloproliferative syndrome

This study investigated the acute effects of interferon-alpha 2 (IFN-alpha 2) on hormonal secretion in adult patients affected by a chronic myeloproliferative syndrome and tried to shed some light on the mechanism by which IFN-alpha 2 stimulates cortisol and GH secretion in humans. We compared the pattern of IFN-alpha 2-induced cortisol and GH release with that elicited after the same challenge given subsequent to pretreatment with dexamethasone (Dex). We studied eight patients affected by a chronic myeloproliferative syndrome (thrombocythemia) who had been selected for treatment with IFN-alpha 2. Four sets of experiments were performed: 1) 2 mL iv saline was given at 0800 h in eight cases; 2) 3 x 10(6) IU iv IFN-alpha 2 was given at 0800 h in eight cases; 3) 3 x 10(6) IU iv IFN-alpha 2 was given at 0800 h after pretreatment with 1.5 mg Dex (1 mg at midnight the previous night and 0.5 mg at 0700 h on the day of the test) in six cases; and 4) 2 mL iv saline was given at 0800 h after the same Dex pretreatment in four cases. Cortisol and GH were measured in plasma samples drawn at 30-min intervals between 0800 and 1300 h. Acute iv administration of IFN-alpha 2 stimulated the release of both cortisol and GH in each patient with a significant increment vs. control values, as assessed by areas under the curve. The administration of Dex significantly decreased basal plasma cortisol secretion and abolished cortisol response to IFN-alpha 2 administration. These data suggest that the stimulatory action of IFN-alpha 2 on cortisol release is mediated via a modulation of the activity of the hypothalamic-pituitary axis rather than through a direct effect at the level of the adrenal cortex. After Dex plus saline administration, no significant effect was observed on plasma GH levels, which remained low. Dex administration significantly decreased GH response to IFN-alpha 2. These data suggest that a hypothalamic or pituitary stimulation (or both) is involved in the mechanism of IFN-alpha 2-induced GH secretion. It remains to be established whether IFN-alpha 2 directly stimulates pituitary somatotropic cells or whether the cytokine exerts a stimulatory action on GH secretion by indirectly modulating the hypothalamic or pituitary activity. In conclusion, acute iv administration of IFN-alpha 2 represents a potent stimulus for cortisol and GH secretion in adult human subjects.(ABSTRACT TRUNCATED AT 400 WORDS)