Effect of ethanol/TEOS ratios and amount of ammonia on the properties of copper-doped calcium silicate nanoceramics.

Calcium magnesium silicate glasses could be suggested for the synthesis of scaffolds for hard tissue regeneration, as they present a high residual glassy phase, high hardness values and hydroxyapatite-forming ability. The use of trace elements in the human body, such as Cu, could improve the biological performance of such glasses, as Cu is known to play a significant role in angiogenesis. Nano-bioceramics are preferable compared to their micro-scale counterparts, because of their increased surface area, which improves both mechanical properties and apatite-forming ability due to the increased nucleation sites provided, their high diffusion rates, reduced sintering time or temperature, and high mechanical properties. The aim of the present work was the evaluation of the effect of different ratios of Ethanol/TEOS and total amount of the inserted ammonia to the particle size, morphology and bioactive, hemolytic and antibacterial behavior of nanoparticles in the quaternary system SiO2-CaO-MgO-CuO. Different ratios of Ethanol/TEOS and ammonia amount affected the size and morphology of bioactive nanopowders. The optimum materials were synthesized with the highest ethanol/TEOS ratio and ammonia amount as verified by the enhanced apatite-forming ability and antibacterial and non-hemolytic properties.

Composite PLGA-Nanobioceramic Coating on Moxifloxacin-Loaded Akermanite 3D Porous Scaffolds for Bone Tissue Regeneration.

Silica-based ceramics doped with calcium and magnesium have been proposed as suitable materials for scaffold fabrication. Akermanite (Ca2MgSi2O7) has attracted interest for bone regeneration due to its controllable biodegradation rate, improved mechanical properties, and high apatite-forming ability. Despite the profound advantages, ceramic scaffolds provide weak fracture resistance. The use of synthetic biopolymers such as poly(lactic-co-glycolic acid) (PLGA) as coating materials improves the mechanical performance of ceramic scaffolds and tailors their degradation rate. Moxifloxacin (MOX) is an antibiotic with antimicrobial activity against numerous aerobic and anaerobic bacteria. In this study, silica-based nanoparticles (NPs) enriched with calcium and magnesium, as well as copper and strontium ions that induce angiogenesis and osteogenesis, respectively, were incorporated into the PLGA coating. The aim was to produce composite akermanite/PLGA/NPs/MOX-loaded scaffolds through the foam replica technique combined with the sol-gel method to improve the overall effectiveness towards bone regeneration. The structural and physicochemical characterizations were evaluated. Their mechanical properties, apatite forming ability, degradation, pharmacokinetics, and hemocompatibility were also investigated. The addition of NPs improved the compressive strength, hemocompatibility, and in vitro degradation of the composite scaffolds, resulting in them keeping a 3D porous structure and a more prolonged release profile of MOX that makes them promising for bone regeneration applications.

Mechanical and thermal properties of PMMA resin composites for interim fixed prostheses reinforced with calcium ß-pyrophosphate.

Interim restorations are essential in fixed prosthodontics as they provide temporary protection of teeth before the insertion of the permanent restoration. Poly(methyl methacrylate) (PMMA) is widely used in the fabrication of interim-fixed restorations as it is a biocompatible material with a lot of convenient properties. However, it exhibits low impact and tensile strength and therefore it is necessary to be reinforced. Calcium ß-pyrophosphate (ß-CPP) is considered a promising reinforcing material for dental applications, especially for enamel regeneration due to its stability at low pH and its low wear rate. The aim of this study was to manufacture PMMA/ß-CPP composites suitable for fixed-interim restorations and to study their mechanical and thermal properties. In order to enhance ß-CPP dispersion into PMMA matrix, ball-milling was performed for 1 or 6 h. Three-point bending test was performed to study flexural strength, Dynamic Mechanical Analysis (DMA) to reveal the elastic and viscous moduli along with Tg, Fourier Transform Infrared Spectroscopy (FTIR) and X-Ray Diffraction Analysis (XRD) to investigate the structure of the materials and SEM for the morphological evaluation of both composite powders and polymerized specimens. Thermogravimetric Analysis (TGA) and Differential Scanning Calorimetry (DSC) experiments were performed to study their thermal properties. A statistically significant increase in flexural strength was found in the 0.5, 0.75 and 1% composite groups after 6 h ball-milling, relative to the control, with the 6 h ball milling mixed specimens, presenting the highest flexural strength values. The brittle fracture type was common to all groups. An obvious improvement of the mechanical properties and a slight improvement in the thermal stability of the composite materials values were also observed as ß-CPP content was increased, while Tg values were statistically not-affected.

Synthesis, Thermal Properties and Decomposition Mechanism of Poly(Ethylene Vanillate) Polyester.

Plastics are perceived as modern and versatile materials, but their use is linked to numerous environmental issues as their production is based on finite raw materials (petroleum or natural gas). Additionally, their low biodegradability results in the accumulation of microplastics. As a result, there is extensive interest in the production of new, environmentally friendly, bio-based and biodegradable polymers. In this context, poly(ethylene vanillate) (PEV) has a great potential as a potentially bio-based alternative to poly(ethylene terephthalate); however, it has not yet been extensively studied. In the present work, the preparation of PEV is reported. The enthalpy and the entropy of fusion of the pure crystalline PEV have been estimated for the first time. Additionally, the equilibrium melting temperature has also been calculated. Furthermore, the isothermal and non-isothermal crystallization behavior are reported in detail, and new insights on the thermal stability and degradation mechanism of PEV are given.

Unraveling the materials and techniques of post-Byzantine wall paintings: Is there a sole pictorial phase at the catholicon of Stomion, Central Greece?

Saint Demetrius of Stomion is a historical monastery placed in the geographical area of Larissa town, Greece, with a remarkable presence from its founding until nowadays. The monastery's present catholicon (main church) has been dated in the 16th century and its surviving wall paintings were constructed in 1758. In addition to the characterization of the materials applied, the purpose of this study is to determine the existence of a sole pictorial phase, that of the mid-18th century, or the occurrence of overpaintings. Additionally, the present study aims to begin the establishment of the documentation of materials and techniques of the late post-Byzantine iconographic guilds, which acted in Central and Northern Greece. The collected samples were analyzed by means of microscopic, spectroscopic and thermogravimetric methods. The use of fresco technique is implied by the major participation of calcium carbonate in all of the painting layers, its main contribution in the plaster layers and the microstratigraphic analysis of the samples' cross-sections, while the scarce and local presence of a proteinaceous material implies the limited use of egg-tempera technique for the highlights. The pigment analysis shows that mostly traditional pigments were used, including cinnabar, ferrous pigments (ochre, sienna, umber), minium, Naples yellow, massicot/litharge, green earth (celadonite), malachite, carbon and bone black, calcite, kaolinite and lead white. The absence of modern pigments, the consistency of all samples regarding microstratigraphy and applied materials, and the lack of the extensive use of an organic medium, strongly suggest the lack of overpaintings.

Synthesis and Characterization of In-Situ-Prepared Nanocomposites Based on Poly(Propylene 2,5-Furan Dicarboxylate) and Aluminosilicate Clays.

Poly(propylene 2,5-furan dicarboxylate) (PPF), or poly(trimethylene 2,5-furan dicarboxylate) (PTF), is a biobased alipharomatic polyester that is expected to replace its fossil-based terephthalate (PPT) and naphthate (PPN) homologues. PPF possesses exceptional gas barrier properties, but its slow crystallization rate might affect its success in specific applications in the future. Therefore, a series of PPF based nanocomposites with the nanoclays Cloisite®-Na (MMT), Cloisite®-20A (MMT 20A), and halloysite nanotubes (HNT) were synthesized via the in situ transterification and polycondensation method. The effect of the nanoclays on the structure, thermal, and crystallization properties of PPF was studied with several methods including infrared spectroscopy (IR), Nuclear Resonance Spectroscopy (¹H-NMR), Wide Angle X-ray Diffraction (WAXD), Thermogravimetric Analysis (TGA), and Differential Scanning Calorimetry (DSC). The insertion of the nanofillers in the polymer matrix altered the crystallization rates, and TGA results showed good thermal stability, since no significant mass loss occurred up to 300 °C. Finally, the degradation mechanism was studied in depth with Pyrolysis-Gas Chromatography/Mass Spectroscopy, and it was found that ß-scission is the dominant degradation mechanism.