Mechanochemical Synthesis of Resveratrol-Piperazine Cocrystals.

The 1:1 resveratrol-piperazine cocrystal was successfully synthesized and scaled-up to 300 g scale with the mechanochemical method, as a result of investigating key process parameters, namely the solvent and the grinding time. The use of water, ethanol or ethanol-water mixtures and reaction times up to 50 min were evaluated relative to the dry grinding process. Cocrystal formation and purity were monitored through X-ray diffraction and calorimetry measurements. The dry grinding resulted in an incomplete cocrystal formation, while the use of water or water-ethanol mixture yielded a monohydrate solid phase. Pure ethanol was found to be the optimal solvent for large-scale cocrystallization, as it delivered cocrystals with high crystallinity and purity after 10-30 min grinding time at the laboratory scale. Notably, a relatively fast reaction time (30-60 min) was sufficient for the completion of cocrystallization at larger scales, using a planetary ball mill and a plant reactor. Also, the obtained cocrystal increases the aqueous solubility of resveratrol by 6%-16% at pH = 6.8. Overall, this study highlights the potential of solvent-assisted mechanochemical synthesis as a promising new approach for the efficient production of pure resveratrol-piperazine cocrystals.

A 16S rRNA Gene-Based Metabarcoding of Phosphate-Rich Deposits in Muierilor Cave, South-Western Carpathians.

Muierilor Cave is one of Romania's most important show caves, with paleontological and archeological deposits. Recently, a new chamber was discovered in the cave, with unique yellow calcite crystals, fine-grained crusts, and black sediments. The deposits in this chamber were related to a leaking process from the upper level that contains fossil bones and a large pile of guano. Samples were taken from the new chamber and another passage to investigate the relationship between the substrate and microbial community. Chemical, mineralogical, and whole community 16S rRNA gene-based metabarcoding analyses were undertaken, and the base of the guano deposit was radiocarbon dated. Our study indicated bacteria linked to the presence of high phosphate concentration, most likely due to the nature of the substrate (hydroxyapatite). Bacteria involved in Fe, Mn, or N cycles were also found, as these elements are commonly identified in high concentrations in guano. Since no bat colonies or fossil bones were present in the new chamber, a high concentration of these elements could be sourced by organic deposits inside the cave (guano and fossil bones) even after hundreds of years of their deposition and in areas far from both deposits. Metabarcoding of the analyzed samples found that ∼0.7% of the identified bacteria are unknown to science, and ∼47% were not previously reported in caves or guano. Moreover, most of the identified human-related bacteria were not reported in caves or guano before, and some are known for their pathogenic potential. Therefore, continuous monitoring of air and floor microbiology should be considered in show caves with organic deposits containing bacteria that can threaten human health. The high number of unidentified taxa in a small sector of Muierilor Cave indicates the limited knowledge of the bacterial diversity in caves that can have potential applications in human health and biotechnology.

Multifunctional Composite Coatings Based on Photoactive Metal-Oxide Nanopowders (MgO/TiO2) in Hydrophobic Polymer Matrix for Stone Heritage Conservation.

Multifunctional composite coatings composed of metal oxide nanoparticles dispersed in polymer matrices are an advanced solution to solve the problem of stone heritage deterioration. Their innovative design is meant to be stable, durable, transparent, easy to apply and remove, non-toxic, hydrophobic, and permeable. Coating formulations for the protection of buildings and monuments have been intensively researched lately. Such formulations are based on multifunctional composite coatings incorporating metal oxides. The present work aims to combine the hydrophobic properties of sodium polyacrylate (NaPAC16) with the antimicrobial effectiveness, with promising antimicrobial results even in the absence of light, and good compatibility of MgO (a safe to use, low cost and environmentally friendly material) and TiO2 (with antibacterial and antifungal properties), in order to develop coatings for stone materials protection. MgO (pure phase periclase) and TiO2 (pure phase anatase) nanopowders were prepared through sol-gel method, specifically routes. Aqueous dispersions of hydrophobically modified polymer (NaPAC16, polyacrylic acid sodium salt) and MgO/TiO2 nanopowders were deposited through layer-by-layer dip coating technique on glass slides and through immersion on stone fragments closely resembling the mosaic stone from the fourth century AD Roman Mosaic Edifice, from Constanta, Romania. The oxide nanopowders were characterized by: Thermal analysis (TG/DTA), scanning electron microscopy (SEM), X-ray diffraction (XRD), BET specific surface area and porosity, and UV-Vis spectroscopy for band gap determination. An aqueous dispersion of modified polyacrylate polymer and oxide nanopowders was deposited on different substrates (glass slides, red bricks, gypsum mortars). Film hydrophobicity was verified by contact angle measurements. The colour parameters were evaluated. Photocatalytic and antimicrobial activity of the powders and composite coatings were tested.

Advances in Osteoporotic Bone Tissue Engineering.

The increase in osteoporotic fracture worldwide is urging bone tissue engineering research to find new, improved solutions both for the biomaterials used in designing bone scaffolds and the anti-osteoporotic agents capable of promoting bone regeneration. This review aims to report on the latest advances in biomaterials by discussing the types of biomaterials and their properties, with a special emphasis on polymer-ceramic composites. The use of hydroxyapatite in combination with natural/synthetic polymers can take advantage of each of their components properties and has a great potential in bone tissue engineering, in general. A comparison between the benefits and potential limitations of different scaffold fabrication methods lead to a raised awareness of the challenges research face in dealing with osteoporotic fracture. Advances in 3D printing techniques are providing the ways to manufacture improved, complex, and specialized 3D scaffolds, capable of delivering therapeutic factors directly at the osteoporotic skeletal defect site with predefined rate which is essential in order to optimize the osteointegration/healing rate. Among these factors, strontium has the potential to increase osseointegration, osteogenesis, and healing rate. Strontium ranelate as well as other biological active agents are known to be effective in treating osteoporosis due to both anti-resorptive and anabolic properties but has adverse effects that can be reduced/avoided by local release from biomaterials. In this manner, incorporation of these agents in polymer-ceramic composites bone scaffolds can have significant clinical applications for the recovery of fractured osteoporotic bones limiting or removing the risks associated with systemic administration.

Combined use of Mössbauer spectroscopy, XPS, HRTEM, dielectric and anelastic spectroscopy for estimating incipient phase separation in lead titanate-based multiferroics.

The formation of separate phases in crystalline materials is promoted by doping with elements with different valences and ionic radii. Control of the formation of separate phases in multiferroics is extremely important for their magnetic, ferroelectric and elastic properties, which are relevant for multifunctional applications. The ordering of dopants and incipient phase separation were studied in lead titanate-based multiferroics with the formula (Pb0.88Nd0.08)(Ti0.98-xFexMn0.02)O3 (x = 0.00, 0.03, 0.04, 0.05) by means of a combination of Mössbauer spectroscopy, XPS, HRTEM, dielectric and anelastic spectroscopy. We found that Fe ions are substituted as Fe3+ at Ti sites and preferentially exhibit pentahedral coordination, whereas Ti ions have coexisting valences of Ti4+/Ti3+. Fe3+ ions are preferentially ordered in clusters, and there exists a transition temperature TC1, below which phase separation occurs between a tetragonal phase T1 free of magnetic clusters and a cubic phase, and a lower transition temperature TC2, below which the cubic phase rich in magnetic clusters is transformed into a tetragonal phase T2. The phase separation persists at the nanoscale level down to room temperature and is visible in HRTEM images as a mixing of nanodomains with different tetragonality ratios. This phase separation was observed over the whole studied concentration range of xFe values. It occurs progressively with the value of xFe, and the transition temperature TC2 decreases with the concentration from about 620 K (xFe = 0.03) to about 600 K (xFe = 0.05), while TC1 remains nearly constant.

Aqueous Dispersions of Silica Stabilized with Oleic Acid Obtained by Green Chemistry.

The present study describes for the first time the synthesis of silica nanoparticles starting from sodium silicate and oleic acid (OLA). The interactions between OLA and sodium silicate require an optimal OLA/OLANa molar ratio able to generate vesicles that can stabilize silica particles obtained by the sol-gel process of sodium silicate. The optimal molar ratio of OLA/OLANa can be ensured by a proper selection of OLA and respectively of sodium silicate concentration. The titration of sodium silicate with OLA revealed a stabilization phenomenon of silica/OLA vesicles and the dependence between their average size and reagent's molar ratio. Dynamic light scattering (DLS) and scanning electron microscopy (SEM) measurements emphasized the successful synthesis of silica nanoparticles starting from renewable materials, in mild condition of green chemistry. By grafting octadecyltrimethoxysilane on the initial silica particles, an increased interaction between silica particles and the OLA/OLANa complex was achieved. This interaction between the oleyl and octadecyl chains resulted in the formation of stable gel-like aqueous systems. Subsequently, olive oil and an oleophylic red dye were solubilized in these stable aqueous systems. This great dispersing capacity of oleosoluble compounds opens new perspectives for future green chemistry applications. After the removal of water and of the organic chains by thermal treatment, mesoporous silica was obtained.