Electrospun biodegradable nanofibers scaffolds for bone tissue engineering

Many polymeric materials have been developed and introduced for bone regeneration. Especially, their nanofibrous forms are mostly applied for artificial extracellular matrices. Polymeric materials in their nanofibrous form show some potent properties such as high surface‐to‐volume ratio, tunable porosity, and ease of surface functionalization. Benefiting from the properties of their main polymer and additives, they can provide new opportunities for cell seeding, proliferation, and new 3D‐tissue formation. This article focuses on most cited polymeric nanofibrous scaffolds fabricated by electrospinning and recent achievements. They were divided into two main categories: natural (collagen, silk, keratin, gelatin, chitosan, and alginate) and synthetic (e.g., polycaprolactone, polylactic acid, and polyglycolic acid) polymers. The role of several additives like hydroxyapatite, bone morphogenetic proteins (BMPs), tricalcium phosphate, and collagen type I in improving the adhesion, differentiation, and tissue formation of stem cells were discussed. Finally, the osteogenic capacity and ability of nanofibrous scaffolds to support the growth of clinically relevant bone tissue were briefly studied. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 42883.     

Dynamically vulcanized polypropylene/ethylene‐propylene diene monomer/organoclay nanocomposites: Effect of mixing sequence on structural,rheological, and mechanical properties

Dynamically vulcanized thermoplastic elastomer (TPE) nanocomposites based on polypropylene (PP), ethylene‐propylene diene monomer (EPDM) and cloisite 15A were prepared via direct melt mixing in a co‐rotating twin‐screw extruder. The mixing process was carried out with optimized processing parameters (barrel temperature = 180°C; screw speed = 150 rpm; and feeding rate = 0.2 kg/hr). The formulation used to prepare the nanocomposites was fixed to 75/20/5 (PP/EPDM/Cloisite^©15A), expressed in mass fraction. Effect of mixing sequence on the properties of vulcanized and unvulcanized (TPE) nanocomposites prepared under similar conditions was investigated using X‐ray diffraction (XRD) and a tensile testing machine. Results showed that the sequence of mixing does affect the properties of final TPE nanocomposites. Accordingly, nanocomposite samples prepared through mixing the preblended PP/clay masterbatch with EPDM phase, show better clay dispersion within the polymer matrix. J. VINYL ADDIT. TECHNOL., 22:320–325, 2016. © 2014 Society of Plastics Engineers     

Electrophoretic deposition of bioactive glass nanopowders on magnesium based alloy for biomedical applications

To slow down the initial biodegradation rate of magnesium (Mg) alloy, crystalline nano-sized bioactive glass coating was used to deposit on micro-arc oxidized AZ91 samples via electrophoretic deposition (EPD). Zeta potential and conductivity of the bioactive glass suspension were characterized at various pH values to identify the most stable dispersion conditions. The bone-bonding properties of bioactive glass coated samples were evaluated in terms of apatite-forming ability during the immersion in simulated body fluid (SBF) solution. Results revealed that the ability to form a bioactive glass coating via EPD was influenced by the degree of its crystalline phase composition. Moreover, the potentiodynamic polarization tests recorded significant drops in corrosion current density and corrosion rate of the coated samples which implies a good level of corrosion protective behavior. These preliminary results show that this process will enable the development of Mg implants in the later stage of bone healing.     

High-performance photocatalysts for the selective oxidation of alcohols to carbonyl compounds

With an increase in awareness about the need for green chemistry, there is a shift in focus towards identifying eco-compatible technologies that can improve product yield and eliminate the use or generation of hazardous compounds. An immediate practical example of such an approach is the development of sustainable methods for alcohol oxidation as alternatives to the current processes that are energy intensive and rely on ecotoxic chemicals. In this regard, heterogeneous photocatalysis has been identified as a robust technique to catalyze reactions under benign conditions, which would otherwise require harsh synthesis routes. With the advent of materials sciences and nanotechnology, there has been a tremendous increase in the scope of applicability of photocatalysis in fine chemicals synthesis. Though an attractive choice, much of the fundamental information pertaining to catalyst activity, selectivity and reaction conditions for optimum conversion are still to be investigated for most of these systems. To this end, this review will encompass recent achievements in the selective photocatalytic oxidation of alcohols by harnessing solar radiation as a viable source of energy. The discussion will be arranged based on common types of photocatalysts reported in literature, namely metal oxides (eg, TiO₂ and ZnO, Nb₂O₅), sulphides (eg, CdS, CuS, and Bi₂S₃), and carbonaceous photocatalysts (eg, g-C₃N₄). Several such candidates for photocatalysts will be discussed critically with the aim of providing useful insight into developing selective photocatalysts that can oxidize alcohols via eco-friendly pathways along with high yields.     

A Modified Method for the Determination of N‐Nitrosodiethanolamine in Coconut Diethanolamide Using HPLC with Dual‐Wavelength UV–Vis Detector

A simple and novel method based on high‐performance liquid chromatography with dual‐wavelength ultraviolet detection at 234 and 254 nm has been developed for the determination of underivatized N‐nitrosodiethanolamine in coconut diethanolamide. The correlation coefficient obtained shows that the method is correct.     

Synthesis of novel polyimides containing side‐chain azo‐2‐naphthol moieties

An amine‐ester derivative of isoeugenol was prepared in three steps. This amine‐ester was converted to diazonium salt and subsequently was reacted with 2‐naphthol and a novel isoeugenol ester‐azo derivative as a new monomer was obtained in quantitative yield. This monomer was characterized by high‐field ¹H‐NMR, IR, and elemental analysis and then was used for the preparation of model compound and polymerization reactions. 4‐Phenyl‐1,2,4‐triazoline‐3,5‐dione was allowed to react with this new monomer. The reaction was very fast and gave only one double adduct by Diels–Alder and ene pathways in excellent yield. The polymerization reactions of novel monomer with bistriazolinediones [bis(p‐3,5‐dioxo‐1,2,4‐triazolin‐4‐ylphenyl)methane and 1,6‐bis(3,5‐dioxo‐1,2,4‐triazolin‐4‐yl)hexane] were carried out in N,N‐dimethylacetamide at room temperature. The reactions were exothermic, fast, and gave novel heterocyclic polyimides by repetitive Diels–Alder‐ene polyaddition reactions. Some structural characterization and physical properties of these novel heterocyclic polyimides are reported. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1942–1951, 2003     

Facile synthesis of different morphologies of Te-doped ZnO nanostructures

Te-doped ZnO nanostructures were synthesized by an annealing (vapor–solid) process under ambient conditions, and characterized in terms of their morphological, structural, compositional and optical properties. The structural and morphological characterizations revealed that the synthesized nanostructures were well-defined multipods, needles and spherical particles, and possessed well-crystalline ZnO wurtzite hexagonal phase. Also, in the X-ray diffraction studies, the presence of a shift in the peak positions towards a lower angle, and a decrease in the intensity, with an increase in the Te concentration, as compared to the undoped ZnO, were observed. The chemical composition confirmed the presence of Te, in the case of multipod and needle morphologies. The effect of doping on the crystalline quality and optical properties was also investigated, by using photoluminescence (PL) and Raman spectrometers. The Raman results demonstrated that the doped ZnO nanostructures had a lower crystalline quality than the undoped ZnO. Moreover, the PL results showed a decrease in the band gap for the doped ZnO nanostructures, in comparison to the undoped ZnO. A possible growth mechanism was also proposed.     

Anti‐Oxygen Leaking LiCoO2

LiCoO₂ is a prime example of widely used cathodes that suffer from the structural/thermal instability issues that lead to the release of their lattice oxygen under nonequilibrium conditions and safety concerns in Li‐ion batteries. Here, it is shown that an atomically thin layer of reduced graphene oxide can suppress oxygen release from Li_xCoO₂ particles and improve their structural stability. Electrochemical cycling, differential electrochemical mass spectroscopy, differential scanning calorimetry, and in situ heating transmission electron microscopy are performed to characterize the effectiveness of the graphene‐coating on the abusive tolerance of Li_xCoO₂. Electrochemical cycling mass spectroscopy results suggest that oxygen release is hindered at high cutoff voltage cycling when the cathode is coated with reduced graphene oxide. Thermal analysis, in situ heating transmission electron microscopy, and electron energy loss spectroscopy results show that the reduction of Co species from the graphene‐coated samples is delayed when compared with bare cathodes. Finally, density functional theory and ab initio molecular dynamics calculations show that the rGO layers could suppress O₂ formation more effectively due to the strong C? O_cathode bond formation at the interface of rGO/LCO where low coordination oxygens exist. This investigation uncovers a reliable approach for hindering the oxygen release reaction and improving the thermal stability of battery cathodes.