Development of Bioactive Glass-Collagen-Hyaluronic Acid-Polycaprolactone Scaffolds for Tissue Engineering Applications.

In this work, bioactive glass (BG) particles synthesized by a sol-gel method, hyaluronic acid (HYA) and collagen (COL) extracted from chicken eggshell membrane (ESM), and as-purchased polycaprolactone (PCL) were used to obtain a novel bioactive scaffold using the gel-pressing technique. Two composite mixtures in weight percent were obtained and identified as SCF-1 and SCF-2, and were characterized by using FTIR, XRD, and SEM techniques. Subsequently, the composite materials applied as coatings were evaluated in simulated body fluid solutions using electrochemical techniques. The results of bioactivity and biodegradability evaluations, carried out by immersing in simulated body fluid and phosphate-buffered saline solution, showed that the SCF-1 sample presented the best biocompatibility. In accordance with the potentiodynamic results, the 316L-SS and the SCF-1-coated SS showed a very similar corrosion potential (E corr ), around -228 mV, and current density (i corr ) values in close proximity, while the SCF-2-coated SS showed more positive E corr around -68 mV and lower i corr value in one order of magnitude. These results agree with those obtained by electrochemical impedance spectroscopy, which show a corrosion mechanism governed by activation and finite diffusion through the porous layer. In addition, results were complemented by dynamic compression testing under oscillating forces to identify the developed scaffolds' response under external forces, where the SCF-1 scaffold presented a maximum compression. The degradation resistance, bioactivity, and mechanically obtained measurements provided interesting results for potential further studies in tissue engineering.

Insights Into Oxygen Adsorption on Ag-Cu Nanocluster as an Oxidation Catalyst by Ab Initio Atomistic Thermodynamics.

To understand the catalytic activity of Ag-Cu cluster as catalyst of ethylene oxidation, bare Ag and Cu and Ag core/Cu12 shell and Cu core/Ag12 shell are built and optimized by density functional theory calculations incorporating the effect of the atmospheric environment. Consequently different oxygen adsorption sites on the cluster are considered: top site of the shell atoms, bridge site of the shell atoms and hollow site of the shell atoms. For each adsorption site, a few coverages are considered, both oxygen-rich condition and oxygen-poor condition. The phase diagrams of oxygen and 13-atom Ag-Cu clusters are finally determined. The pressure-temperature phase diagrams are determined for the oxygen and 13-atom Ag-Cu clusters, which reveal important insights into this system and its catalytic properties. The phase diagrams of oxygen and 13-atom Ag-Cu clusters are finally determined. The results predict the most stable phase: structure and adsorption of oxygen at certain temperature and certain pressure. Under oxygen-poor condition, the cluster structures are most likely to be changed. This information must be helpful to understand the catalytic process of Ag-Cu cluster as catalyst of ethylene oxidation.