Composites based on high-density polyethylene,polylactide and calcium carbonate: effect of calcium carbonate nanoparticles as co-compatibilizers

Polymer Bulletin - Investigating the compatibility mechanism of hybrid composites based on two polymers and one mineral nanofiller is a challenge that needs to be better understood. This study...     

An evaluation of Acacia mearnsii tannin as an aluminum corrosion inhibitor in acid,alkaline, and neutral media

The electrochemical behavior of aluminum in tannin from Acacia mearnsii bark was evaluated by potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) in media under three different pH conditions: acid, alkaline, and neutral. A relationship among pH, polymerization grade (PG), zeta potential, surface, and electrochemical properties was observed in the inhibition performance of the tannin. At high pH, the oligomer structure of the tannin was affected, resulting in a low PG (4) and high zeta potential (−75 mV), and consequently, the inhibition efficiency decreased (68%) in comparison with that in acid (99%) and neutral media (96%). The values obtained indicate a physisorption mechanism for the aluminum corrosion inhibition in the studied conditions.     

Effect of N-Vinyl-2-Pyrrolidone (NVP), a Bromodomain-Binding Small Chemical,on Osteoblast and Osteoclast Differentiation and Its Potential Application for Bone Regeneration

The human skeleton is a dynamic and remarkably organized organ system that provides mechanical support and performs a variety of additional functions. Bone tissue undergoes constant remodeling; an essential process to adapt architecture/resistance to growth and mechanical needs, but also to repair fractures and micro-damages. Despite bone’s ability to heal spontaneously, certain situations require an additional stimulation of bone regeneration, such as non-union fractures or after tumor resection. Among the growth factors used to increase bone regeneration, bone morphogenetic protein-2 (BMP2) is certainly the best described and studied. If clinically used in high quantities, BMP2 is associated with various adverse events, including fibrosis, overshooting bone formation, induction of inflammation and swelling. In previous studies, we have shown that it was possible to reduce BMP2 doses significantly, by increasing the response and sensitivity to it with small molecules called “BMP2 enhancers”. In the present study, we investigated the effect of N-Vinyl-2-pyrrolidone (NVP) on osteoblast and osteoclast differentiation in vitro and guided bone regeneration in vivo. We showed that NVP increases BMP2-induced osteoblast differentiation and decreases RANKL-induced osteoclast differentiation in a dose-dependent manner. Moreover, in a rabbit calvarial defect model, the histomorphometric analysis revealed that bony bridging and bony regenerated area achieved with NVP-loaded poly (lactic-co-glycolic acid (PLGA) membranes were significantly higher compared to unloaded membranes. Taken together, our results suggest that NVP sensitizes BMP2-dependent pathways, enhances BMP2 effect, and inhibits osteoclast differentiation. Thus, NVP could prove useful as “osteopromotive substance” in situations where a high rate of bone regeneration is required, and in the management of bone diseases associated with excessive bone resorption, like osteoporosis.     

Characterisation of cellulose-hydrolysing enzymes from the fungus Bipolaris sorokiniana

Cellulose-hydrolysing enzymes from the phytopathogenic fungus Bipolaris sorokiniana were partially purified and characterised. The enzyme production was variable according to the carbon source. β-Glucosidase and cellobiohydrolase activities were higher by growing the fungus on cellulose than on other carbon sources. Carboxymethyl cellulase production was stimulated by other carbohydrates, mainly lactose. Partial enzyme purification was carried out by liquid chromatography on Sepharose CL4B. The purification was about 17-fold, with a yield of 41% as judged by assay with p-nitrophenyl-β-D -glucopyranoside as substrate. The optimum pH and temperature were 5.0 and 55–60 °C respectively. The enzyme was stable at 28 and 37 °C but lost about 50% of its initial activity after 120 min at 55 °C. Saccharification of cellulosic materials such as crystalline cellulose, filter paper and wheat straws was carried out using the partially purified enzyme, resulting in the production of reducing sugars. © 1999 Society of Chemical Industry