Bioactive glasses: from parent 45S5 composition to scaffold-assisted tissue-healing therapies

Nowadays, bioactive glasses (BGs) are mainly used to improve and support the healing process of osseous defects deriving from traumatic events, tumor removal, congenital pathologies, implant revisions, or infections. In the past, several approaches have been proposed in the replacement of extensive bone defects, each one with its own advantages and drawbacks. As a result, the need for synthetic bone grafts is still a remarkable clinical challenge since more than 1 million bone-graft surgical operations are annually performed worldwide. Moreover, recent studies show the effectiveness of BGs in the regeneration of soft tissues, too. Often, surgical criteria do not match the engineering ones and, thus, a compromise is required for getting closer to an ideal outcome in terms of good regeneration, mechanical support, and biocompatibility in contact with living tissues. The aim of the present review is providing a general overview of BGs, with particular reference to their use in clinics over the last decades and the latest synthesis/processing methods. Recent advances in the use of BGs in tissue engineering are outlined, where the use of porous scaffolds is gaining growing importance thanks to the new possibilities given by technological progress extended to both manufacturing processes and functionalization techniques

Nucleation Induced Undulative Instability in Thin Films of nCB Liquid Crystals

A surface instability is reported in thin nematic films of 5CB and 8CB, occurring near the nematic--isotropic phase transition. Although this instability leads to patterns reminiscent of spinodal dewetting, we show that it is actually based on a nucleation mechanism. Its characteristic wavelength does not depend markedly on film thickness, but strongly on the heating rate.Comment: 4 pages, 5 figure

Fluid-Assisted Strain Localization in Quartz at the Brittle/Ductile Transition

A mylonitic quartzite with conjugate and synthetic shear bands was investigated by Electron Backscatter Diffraction and optical microscopy to obtain insights on recrystallization mechanisms and strain localization in quartz at plastic to semibrittle conditions close to the brittle-ductile transition. The mylonitic quartzite deformed during late Miocene thrusting coeval with contact metamorphism in the high-strain domains of the Calamita Schists (Elba Island, Italy). Mylonitic deformation occurred from amphibolite to lower greenschist facies conditions during cooling of the aureole. Dynamic recrystallization, dominated by the activity of dislocation creep by prism slip, produced recrystallized quartz layers mantling relic large quartz porphyroclasts. Under decreasing temperature and fluid-rich conditions, quartz porphyroclasts acted as relatively rigid bodies and fractured along synthetic and conjugate C′ shear bands. Shear bands developed along kinematically favored orientations, just locally assisted by weak crystallographic planes in quartz. Fracturing along shear bands was assisted by cataclasis and fluid infiltration enhancing fracture propagation and healing by recrystallization and authigenesis of new quartz and phyllosilicate grains. The process enhanced the propagation of and strain localization in shear bands, with the development of bands of weak phyllosilicates. Furthermore, we observed the development of a c axis preferred orientation (CPO) related to dissolution and precipitation of new grains with their c axis oriented parallel to shear bands. This study highlights the importance of the interplay between brittle and crystal-plastic processes and fluid ingress in the semibrittle regime to understand deformation partitioning and strain localization

Double-difference tomography at Mt. Etna volcano

Double-difference tomography at Mt Etna volcano was realized by using the tomographic algorithm developped by Monteiller et al. (2005), in which the travel-time computation was performed using a finite-difference solution of the Eikonal equation (Podvin and Lecomte, 1991) and a posteriori ray-tracing. The inverse problem was solved using a probabilistic approach (Tarantola and Valette, 1982). The optimal a priori information (correlation length and a priori model variance) was found experimentally by performing tomographies for correlation lengths and variances varying in large intervals. This probabilistic approach allowed us to use a sech pdf for representing errors in differential times. Data were travel-times and time delays provided by a set of 329 earthquakes, well-recorded by the INGV-CT seismic network (50 stations) on the Mt Etna volcano during the seismo-volcanic crisis occurring between October 2002 and January 2003. Checkerboard tests realized with this geometry and earthquake pairs showed that the model can be correctly reconstructed in a significant area around Mt Etna volcano. Results of the P and S-wave double-difference tomography clearly evidenced two concentric features: a fast central cylindrical core, probably of intrusive origin, surrounded by a slow annealed body, which could be related to partial melting

Double-difference tomography at Mt Etna volcano: Preliminary results

We performed a preliminary double-difference tomographic study using earthquake data recorded by the INGV-Catania seismic network during the large seismic and eruptive crisis of 2002-2003 at Mt Etna volcano. Compared to previous models, first results presented from the inversion of travel-time differences, tend to show an increase in the velocity contrast between the fast core and the slow periphery of the volcano

Albumin and fibronectin adsorption on treated titanium surfaces for osseointegration: An advanced investigation

Protein adsorption has a central role in the outcome of implants. However, there is no consensus about the impact of the different surface properties on the material-protein interactions. Here, the adsorption of albumin and fibmnectin in near-physiological concentration is investigated on three differently treated titanium-based surfaces and compared after a thorough characterization. The different titanium surfaces have very different surface properties, in particular regarding roughness, oxide porosity, wettability, surface energy, and zeta potential, which are all known to deeply affect protein adsorption. By merging several characterization techniques, some conventional and some innovative, it was possible to discriminate the effect of surface properties on different aspects of protein adsorption. Despite forming a continuous layer on all samples, the amount of proteins bound to the surface is mainly due to surface roughness and topography, which can overcome the effect of wettability and surface energy. On the other hand, the secondary structure of albumin and fibmnectin and their orientation are determined by the hydroxyl groups exposed on the surfaces, depending on their surface concentration and acidic reactivity in the former, and the surface zeta potential in the latter

Competitive surface colonization of antibacterial and bioactive materials doped with strontium and/or silver ions

Nowadays, there is a large amount of research aimed at improving the multifunctional behavior of the biomaterials for bone contact, including the concomitant ability to induce apatite formation (bioactivity), fast and effective osteoblasts colonization, and antibacterial activity. The aim of this study is to develop antibacterial and bioactive surfaces (Ti6Al4V alloy and a silica-based bioactive glass) by chemical doping with strontium and/or silver ions. The surfaces were characterized by Scanning Electron Microscopy equipped with Energy Dispersive X ray Spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS), and Transmission Electron Microscopy (TEM). To better focus on the cells–bacteria competition for the implant surface, in addition to the standard assays for the evaluation of the bacteria adhesion (ISO22196) and for single-cell cultures or biofilm formation, an innovative set of co-cultures of cells and bacteria is here proposed to simulate a competitive surface colonization. The results suggest that all the bioactive tested materials were cytocompatible toward the bone progenitor cells representative for the self-healing process, and that the doped ones were effective in reducing the surface colonization from a pathogenic drug-resistant strain of Staphylococcus aureus. The co-cultures experiments demonstrated that the doped surfaces were able to protect the adhered osteoblasts from the bacteria colonization as well as prevent the infection prior to the surface colonization by the osteoblasts