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AFM was used to collect the whole force-deformation cell curves. They provide both the elasticity and adhesion behavior of mouse primary cardiac fibroblasts. To confirm the hypothesis that a link exists between the membrane receptors and the cytoskeletal filaments causing therefore changing in both elasticity and adhesion behavior, actin-destabilizing Cytochalsin D was administrated to the fibroblasts. From immunofluorescence observation and AFM loading/unloading curves, cytoskeletal reorganization as well as a change in the elasticity and adhesion was indeed observed. Elasticity of control fibroblasts is three times higher than that for fibroblasts treated with 0.5 μM Cytochalasin. Moreover, AFM loading-unloading curves clearly show the different mechanical behavior of the two different cells analyzed: (i) for control cells the AFM cantilever rises during the dwell time while cells with Cytochalasin fail to show such an active resistance; (ii) the maximum force to deform control cells is quite higher and as far as adhesion is concern (iii) the maximum separation force, detachment area and the detachment process time are much larger for control compared to the Cytochalasin treated cells. Therefore, alterations in the cytoskeleton suggest that a link must exist between the membrane receptors and the cytoskeletal filaments beneath the cellular surface and inhibition of actin polymerization has effects on the whole cell mechanical behavior as well as adhesion.

Research demonstrates that in the alumina matrix, prepared by using fine and coarse molybdenum particles, the toughness is directly related to the amount of molybdenum metal and the bridging stress is higher with coarse particles. Data suggest that the best microstructure is achieved when the metal particle size is more than 5 micrometer.

Byline: E. Luccini, S. Meriani, O. Sbaizero Ceria zirconia precursors were obtained by applying the urea hydrolysis method to Zr-oxychloride and Ce-nitrate solutions. Dewatering-dying procedures, such as freeze drying (FD) and acetone-toluene-acetone (ATA), were compared with the usual thermal method to assess their suitability for yielding fine, aggregate-free powders for the preparation of ceria-zirconia sinters. The characteristics of the powders before and after calcinations are discussed. The advantage of the ATA method is based on the fact that the formation of hard agglomerates is avoided, high specific surface is achieved and the tetragonal form was the only phase crystallizing on calcination of the chemical precursor.

Byline: S. Maschio, O. Sbaizero, S. Meriani Sinter-reactive powders of α-alumina have been prepared effectively by the decomposition of aluminium basic carbonates. In this work we have studied the urea CO(NH.SUB.2).SUB.2 homogeneous hydrolysis method, applied to alum solutions, KAl(SO.SUB.4).SUB.2 * 12H.SUB.20, using various urea and alum ratios, to precipitate aluminium basic carbonates. The thermal decomposition of the aluminium precipitates, produces fine alumina powders that are suitable for ceramic purposes.

Byline: S. Maschio, O. Sbaizero, S. Meriani In this investigation a series of Al.SUB.2O.SUB.3-ZrO.SUB.2, composites materials were prepared using unstabilised ZrO.SUB.2 or different amount of either Y.SUB.2O.SUB.3 or CeO.SUB.2 for stabilising the ZrO.SUB.2 in its metastable tetragonal form. The mechanical properties (hardness, bend strength and toughness) were measured and the influence of the different micro structure obtained as well as the role of phase transformation and micro cracks has been assessed.

Mechanical stimulation appears to be a critical modulator for many aspects of biology, both of living tissue and cells. The cell-stretcher, a novel device for the mechanical uniaxial stimulation of populations of cells, is described. The system is based on a variable stroke cam-lever-tappet mechanism which allows the delivery of cyclic stimuli with frequencies of up to 10 Hz and deformation between 1% and 20%. The kinematics is presented and a simulation of the dynamics of the system is shown, in order to compute the contact forces in the mechanism. The cells, following cultivation and preparation, are plated on an ad hoc polydimethylsiloxane membrane which is then loaded on the clamps of the cell-stretcher via force-adjustable magnetic couplings. In order to show the viability of the experimentation and biocompatibility of the cell-stretcher, a set of two in vitro tests were performed. Human epithelial carcinoma cell line A431 and Adult Mouse Ventricular Fibroblasts (AMVFs) from a dual reporter mouse were subject to 0.5 Hz, 24 h cyclic stretching at 15% strain, and to 48 h stimulation at 0.5 Hz and 15% strain, respectively. Visual analysis was performed on A431, showing definite morphological changes in the form of cellular extroflections in the direction of stimulation compared to an unstimulated control. A cytometric analysis was performed on the AMVF population. Results show a post-stimulation live-dead ratio deviance of less than 6% compared to control, which proves that the environment created by the cell-stretcher is suitable for in vitro experimentation. [ABSTRACT FROM AUTHOR]

Discontinuously reinforced aluminium (DRA) composites were prepared by a novel ion exchange process in which the reinforcing phase, aluminium oxide, was introduced by exchanging the magnesium ions in magnesium aluminate spinel with aluminium [1]. The exchange reaction occurs by the diffusion of magnesium and aluminium ions across the interface in opposite directions. The process led to the formation of DRA composites with a remarkable resistance to high temperature deformation. We present an ab-initio density functional study of the coherent cube-on-cube interfaces between spinel (MgAl2O4) and Al metal and relevant X-ray diffraction studies of the DRA composite. We find that the presence of surface electric dipoles near the interface, originated by the ion exchange process, leads to a lowering of the Al/MgAl2O4 interface toughness, and an increased residual surface stress, which does not support the hypothesis that the ion exchange process is directly responsible for the increased creep resistance of the DRA composite. We propose instead that deep diffusion of the Al atoms into MgAl2O4, resulting in the formation of γ-Al2O3 nanograins, is the mechanism that impedes dislocation movement and thus increases the interface toughness. [ABSTRACT FROM AUTHOR]

Alumina matrix was added with metal molybdenum and different amounts of zirconia''s particles. R-curves were measured during stable crack propagation and a piezo-spectroscopic technique has been used to assess the bridging stresses developed along the crack wake at the critical condition for crack propagation. The theoretical R-curves calculated from the average (microscopic) bridging stress distribution obtained by in situ Raman spectroscopy were in good agreement with the experimental data. If the molybdenum content is kept constant but the ZrO2 amount is increased, the toughening due to t-m transformation increases, but at the same time the metal/ceramic interface is weakened by the presence of zirconia and the toughening due to metal particles bridging decreases. As a result of that, the presence of zirconia has only a limited beneficial influence on the overall toughness. The overall composite toughness is due to transformation and bridging toughening mechanisms, however, the two mechanisms do not have synergistic effects and crack bridging by molybdenum particles appears to be the dominant toughening mechanism. [Copyright &y& Elsevier]

Di Lenarda R, Cadenaro M, Sbaizero O. Effectiveness of 1 mol L- 1 citric acid and 15% EDTA irrigation on smear layer removal. International Endodontic Journal, 33, 46–52, 2000. Aim The aim of this study was to evaluate in vitro the cleansing and smear layer removal capability of alternate canal irrigation with citric acid and NaOCl. Methodology Eighty-one teeth were divided into three groups on the basis of the type of instrumentation, namely, manual stainless steel, Ni-Ti mechanized ProFile .04 taper or MACXim. The groups were further divided on the basis of irrigation protocol: 5% NaOCl alone, NaOCl alternated with 1 mol L-1 citric acid solution or a combination of 15% EDTA and Cetrimide solution. After longitudinal sectioning, dentinal walls were microphotographed with scanning electron microscopy at ×300 and ×1000 magnifications. Qualitative and quantitative cleansing level evaluations were performed using computerized image analysis software. Data were statistically evaluated using Kruskal–Wallis analysis and t-test. Results Qualitative evaluation at ×300 and ×1000 showed no statistically significant differences in cleansing ability between citric acid, EDTA and NaOCl groups. Quantitative evaluation of smear layer removal, measured as open tubules/total dentinal surface ratio, showed that 1 mol L-1 citric acid solution was comparable to EDTA (11.97% vs. 10.36%) (NS); in samples treated with ProFile .04 taper instruments citric acid was most effective (16.17%), whilst in the group treated with manual instrumentation EDTA and Cetrimide were the most effective (11.94%). Specimens irrigated with 5% NaOCl demonstrated significantly more cleansing than those obtained in the other two groups (P <0.001). Conclusions 1 mol L-1 citric acid solution was as effective in removing smear layer as EDTA, but was superior in specimens treated with ProFile .04 taper instruments. [ABSTRACT FROM AUTHOR]

Cardiac fibrosis refers to the abnormal accumulation of extracellular matrix within the cardiac muscle, leading to increased stiffness and impaired heart function. From a rheological standpoint, knowledge about myocardial behavior is still lacking, partially due to a lack of appropriate techniques to investigate the rheology of in vitro cardiac tissue models. 3D multicellular cardiac spheroids are powerful and versatile platforms for modeling healthy and fibrotic cardiac tissue in vitro and studying how their mechanical properties are modulated. In this study, cardiac spheroids were created by co-culturing neonatal rat ventricular cardiomyocytes and fibroblasts in definite ratios using the hanging-drop method. The rheological characterization of such models was performed by Atomic Force Microscopy-based stress-relaxation measurements on the whole spheroid. After strain application, a viscoelastic bi-exponential relaxation was observed, characterized by a fast relaxation time (τ 1 ) followed by a slower one (τ 2 ). In particular, spheroids with higher fibroblasts density showed reduction for both relaxation times comparing to control, with a more pronounced decrement of τ 1 with respect to τ 2 . Such response was found compatible with the increased production of extracellular matrix within these spheroids, which recapitulates the main feature of the fibrosis pathophysiology. These results demonstrate how the rheological characteristics of cardiac tissue vary as a function of cellular composition and extracellular matrix, confirming the suitability of such system as an in vitro preclinical model of cardiac fibrosis., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Published by Elsevier Ltd.)