3d printing in alginic acid bath of in-situ crosslinked collagen composite scaffolds

Bone-tissue regeneration is a growing field, where nanostructured-bioactive materials are designed to replicate the natural properties of the target tissue, and then are processed with technolo-gies such as 3D printing, into constructs that mimic its natural architecture. Type I bovine collagen formulations, containing functional nanoparticles (enriched with therapeutic ions or biomolecules) or nanohydroxyapatite, are considered highly promising, and can be printed using support baths. These baths ensure an accurate deposition of the material, nonetheless their full removal post-printing can be difficult, in addition to undesired reactions with the crosslinking agents often used to improve the final structural integrity of the scaffolds. Such issues lead to partial collapse of the printed constructs and loss of geometrical definition. To overcome these limitations, this work presents a new alternative approach, which consists of adding a suitable concentration of crosslinking agent to the printing formulations to promote the in-situ crosslinking of the constructs prior to the removal of the support bath. To this aim, genipin, chosen as crosslinking agent, was added (0.1 wt.%) to collagen-based biomaterial inks (containing either 38 wt.% mesoporous bioactive glasses or 65 wt.% nanohydroxyapatite), to trigger the crosslinking of collagen and improve the stability of the 3D printed scaffolds in the post-processing step. Moreover, to support the material deposition, a 15 wt.% alginic acid solution was used as a bath, which proved to sustain the printed structures and was also easily removable, allowing for the stable processing of high-resolution geometries

Multifunctional Heterogeneous Catalysts for the Selective Conversion of Glycerol into Methyl Lactate

Multifunctional catalytic systems consisting of physical mixtures of Au nanoparticles (2–3 nm) supported on metal oxides and Sn-MCM-41 nanoparticles (50–120 nm) were synthesized and investigated for the selective conversion of glycerol to methyl lactate. The Au catalyst promotes the oxidation of glycerol to trioses, whereas the solid acid Sn-MCM-41 catalyzes the rearrangement of the intermediate trioses to methyl lactate. Among the supported Au nanoparticles, Au/CuO led to the highest yield and selectivity toward methyl lactate, while the Sn-MCM-41 nanoparticles showed much better catalytic performance than a benchmark solid acid catalyst (USY zeolite). The activity of the multifunctional catalytic system was further optimized by tuning the calcination temperature, the gold loading in the Au/CuO catalyst, and the Au/Sn molar ratio, reaching 63% yield of methyl lactate (ML) at 95% glycerol conversion. This catalytic system also showed excellent reusability. The catalytic results were rationalized on the basis of a detailed characterization by means of TEM, N₂-physisorption, UV–vis spectroscopy, and by FT-IR using probe molecules (CO and ethanol)

High surface area, nanostructured boehmite and alumina catalysts:Synthesis and application in the sustainable epoxidation of alkenes

We report a new, straightforward and inexpensive sol-gel route to prepare boehmite nanorods [gamma-AlO(OH)-NR] with an average length of 23 nm +/- 3 nm, an average diameter of 2 nm +/- 0.3 nm and a high specific surface area of 448 m(2)/g, as evidenced by TEM and N-2-physisorption, respectively. The boehmite was converted to gamma-alumina with preserved nanorod morphology (gamma-Al2O3-NR) and high surface area upon calcination either at 400 or 600 degrees C. These nanostructured materials are active and selective heterogeneous catalysts for the epoxidation of alkenes with the environmentally friendly H2O2. The best catalyst, gamma-Al2O3-NR-400, showed to be versatile in the scope of alkenes that could be converted selectively to their epoxide and displayed enhanced reusability compared to previously reported alumina catalysts. Furthermore, the catalytic performance of the material was enhanced by optimising the reaction conditions such as the solvent and the type of hydrogen peroxide source. Under the optimised reaction conditions, the gamma-Al2O3-NR-400 catalyst displayed 58% cyclooctene oxide yield after 4h of reaction at 80 degrees C with full selectivity towards the epoxide product. The correlation between the catalytic activity of these materials and their physicochemical properties such as surface area, hydrophilicity and number and type of acid sites was critically discussed based on a detailed characterisation study

Assessment of kinetic model for ceria oxidation for chemical-looping CO2 dissociation

Chemical looping technologies are identified as to have an excellent potential for CO2 capture and fuels synthesis. Oxygen carriers are the fundamental component of a chemical looping process, and the choice of stable and efficient carriers with fast redox kinetics is the key to the successful design of the process. Hence, understanding the reaction kinetics is of paramount importance for the selection of an appropriate oxygen carrier material. This work provides a method for kinetic model selection based on a statistical approach to identify the reaction mechanism. The study experimentally investigates the oxidation kinetics of CeO2-d by CO2 and applies a statistical method for the selection of the best-fitting kinetic model for the reaction. The kinetic study is performed in the temperature range of 700–1000¿°C with a CO2 concentration between 20 and 40¿vol% in the feed. The measured peak rates of CO production on ceria were influenced both by temperature and concentration of reactant. The total CO production was more influenced by the temperature than by CO2 concentration, with a maximum CO yield of 33.66¿ml/g at 1000¿°C and 40% CO2. The identification of the oxidation kinetic model is performed by fitting different reactions models to the measured reaction rates and statistically comparing them using the Residual sum of squares (RSS), Akaike information criterion (AICc) and the F-test for the selection of the best-fitting one. Models corresponding to the nucleation and grain growth reaction mechanism provided a good fit of the data, with the Sestak-Berggren (SB) model showing the best approximation of the measured rate of reaction with an evaluated activation energy of 79.1¿±¿6.5¿kJ/mol for the CO2 oxidation.Peer ReviewedPostprint (author's final draft

Ag modified mesoporous bioactive glass nanoparticles for enhanced antibacterial activity in 3D infected skin model

Bioactive glasses (BG) are versatile materials for various biomedical applications, including bone regeneration and wound healing, due to their bone bonding, antibacterial, osteogenic, and angiogenic properties. In this study, we aimed to enhance the antibacterial activity of SiO2-CaO mesoporous bioactive glass nanoparticles (MBGN) by incorporating silver (Ag) through a surface modification approach. The modified Ag-containing nanoparticles (Ag-MBGN) maintained spherical shape, mesoporous structure, high dispersity, and apatite-forming ability after the surface functionalization. The antibacterial activity of Ag-MBGN was assessed firstly using a planktonic bacteria model. Moreover, a 3D tissue-engineered infected skin model was used for the first time to evaluate the antibacterial activity of Ag-MBGN at the usage dose of 1 mg/mL. In the planktonic bacteria model, Ag-MBGN exhibited a significant antibacterial effect against both Pseudomonas aeruginosa and Staphylococcus aureus in comparison to non-engineered (Ag-free) MBGN and the blank control. Moreover, Ag-MBGN did not show cytotoxicity towards fibroblasts at the usage dose. However, in the 3D infected skin model, Ag-MBGN only demonstrated antibacterial activity against S. aureus whereas their antibacterial action against P. aeruginosa was inhibited. In conclusion, surface modification by Ag incorporation is a feasible approach to enhance the antibacterial activity of MBGN without significantly impacting their morphology, polydispersity, and apatite-forming ability. The prepared Ag-MBGN are attractive building blocks for the development of 3D antibacterial scaffolds for tissue engineering

Teacher confidence in professional training: The predictive roles of engagement and burnout

Teachers' work engagement positively impacts teachers' attitudes towards their job. Nevertheless, teachers may experience burnout during their career, which negatively impacts their professional learning opportunities. In this study we investigated the relationship between teachers' levels of burnout, work engagement, and their confidence in in-service training in a sample of Italian teachers. We expected that burnout mediated the relationship between work engagement and teachers' confidence in training. A total of 481 teachers completed self-report questionnaires about engagement and burnout, with an ad hoc Confidence in Training Index developed to assess their attitudes towards professional development courses. The mediation analysis confirmed that the teachers' levels of burnout mediated the relationship between their work engagement and their confidence in in-service training. Findings suggest that teacher confidence in policies about professional training should be evaluated by taking into account their level of engagement and burnout

Spike-based coupling between single neurons and populations across rat sensory cortices, perirhinal cortex, and hippocampus

Cortical computations require coordination of neuronal activity within and across multiple areas. We characterized spiking relationships within and between areas by quantifying coupling of single neurons to population firing patterns. Single-neuron population coupling (SNPC) was investigated using ensemble recordings from hippocampal CA1 region and somatosensory, visual, and perirhinal cortices. Within-area coupling was heterogeneous across structures, with area CA1 showing higher levels than neocortical regions. In contrast to known anatomical connectivity, between-area coupling showed strong firing coherence of sensory neocortices with CA1, but less with perirhinal cortex. Cells in sensory neocortices and CA1 showed positive correlations between within- and between-area coupling; these were weaker for perirhinal cortex. All four areas harbored broadcasting cells, connecting to multiple external areas, which was uncorrelated to within-area coupling strength. When examining correlations between SNPC and spatial coding, we found that, if such correlations were significant, they were negative. This result was consistent with an overall preservation of SNPC across different brain states, suggesting a strong dependence on intrinsic network connectivity. Overall, SNPC offers an important window on cell-to-population synchronization in multi-area networks. Instead of pointing to specific information-coding functions, our results indicate a primary function of SNPC in dynamically organizing communication in systems composed of multiple, interconnected areas