An injectable chitosan-based hydrogel reinforced by oxidized nanocrystalline cellulose and mineral trioxide aggregate designed for tooth engineering applications

The complex anatomy of teeth limits the accessibility and efficacy of regenerative treatments. Therefore, the application of well-known inducers as injectable hydrogels for the regeneration of the dentin-pulp complex is considered a promising approach. In this regard, this study aimed to develop an injectable hydrogel containing mineral trioxide aggregate (MTA). The injectable chitosan/oxidized-nanocrystalline cellulose/MTA (CS/OCNC/MTA) hydrogels were prepared, and the physicochemical properties of these hydrogels were evaluated by TGA, FTIR, Rheological analysis, and SEM. Moreover, the effect of MTA on the swelling and degradability of scaffolds was assessed. The proliferative effects of synthesized hydrogels were also determined on human dental pulp stem cells (hDPSCs) by MTT assay. For induction of differentiation and biomineralization in these cells, the alkaline phosphatase activity and Alizarin Red S staining tests were performed in the presence of fabricated scaffolds. The proliferation of hDPSCs was significantly increased in the presence of these hydrogels. Moreover, the addition of MTA to hydrogel structure dramatically improved the differentiation of hDPSCs. These results suggested that this novel injectable hydrogel provides appropriate physiochemical properties and can be considered a promising scaffold for regenerative endodontic procedures.

Graphical abstract

     

Triphenylphosphine-Catalyzed Simple Synthesis of Dimethyl 1-Aryl-4-ethoxy-5-oxo-4,5-dihydro-1 H -pyrrole-2,3-dicarboxylates

Ethyl 2-arylamino-2-oxo-acetates undergo a complex reaction with dimethyl acetylenedicarboxylate in the presence of triphenylphosphine to produce dimethyl 1-aryl-4-ethoxy-5-oxo-4,5-dihydro-1 H -pyrrole-2,3-dicarboxylates in good yields. Dynamic NMR study of dimethyl 1-(2-methylphenyl)-4-ethoxy-5-oxo-4,5-dihydro-1 H -pyrrole-2,3-dicarboxylate shows a fairly high energy barrier ( j G p = 53.2 kJmol m 1 ) for rotation around the N-aryl single bond, which leads to an observable atropisomerism.     

Cathodic electrodeposition and characterization of nanostructured Y2O3 from chloride solution Part I: Effect of current density

Nanoparticles, nanospheres and nanorods of Y(OH)₃ and Y₂O₃ were prepared via cathodic electrodeposition from chloride bath through applying different current densities. First, yttrium hydroxide precursors were cathodically grown on the cathode surface at the current densities of 2, 1, 0.5, 0.25 and 0.1 mA cm^?2. Then hydroxide powders were heat-treated at 600°C for 3 h. The composition, crystal structure and morphology of the prepared oxide and hydroxide products were investigated by means of differential scanning calorimetery (DSC), X-ray diffraction (XRD), scanning and transmission electron microscopes (SEM and TEM) and FT-IR spectroscopy. Mechanism of base electrogeneration at the applied conditions, and intercalation of chloride ions in the deposit structure during the electrodeposition were proposed and confirmed by the XRD and TG analyses. The results showed that the structural and morphological properties of the products are directly dictated by the applied current density and it can be recognized as the main factor affecting on the cathodic electrodeposition of Y₂O₃.     

Oligosilanylated Silocanes

A number of mono- and dioligosilanylated silocanes were prepared. Compounds included silocanes with 1-methyl-1-tris(trimethylsilyl)silyl, 1,1-bis[tris(trimethylsilyl)silyl], and 1,1-bis[tris(trimethylsilyl)germyl] substitution pattern as well as two examples where the silocane silicon atom is part of a cyclosilane or oxacyclosilane ring. The mono-tris(trimethylsilyl)silylated compound could be converted to the respective silocanylbis(trimethylsilyl)silanides by reaction with KO^tBu and in similar reactions the cyclosilanes were transformed to oligosilane-1,3-diides. However, the reaction of the 1,1-bis[tris(trimethylsilyl)silylated] silocane with two equivalents of KO^tBu leads to the replacement of one tris(trimethylsilyl)silyl unit with a tert-butoxy substituent followed by silanide formation via KO^tBu attack at one of the SiMe₃ units of remaining tris(trimethylsilyl)silyl group. For none of the silylated silocanes, signs of hypercoordinative interaction between the nitrogen and silicon silocane atoms were detected either in the solid state. by single crystal XRD analysis, nor in solution by ²⁹Si-NMR spectroscopy. This was further confirmed by cyclic voltammetry and a DFT study, which demonstrated that the N-Si distance in silocanes is not only dependent on the energy of a potential N-Si interaction, but also on steric factors and through-space interactions of the neighboring groups at Si and N, imposing the orientation of the p_z(N) orbital relative to the N-Si-X axis.     

Electrochemical preparation of α-Ni(OH)2 ultrafine nanoparticles for high-performance supercapacitors

Well-dispersed nanoparticles of nickel hydroxide were prepared via a simple electrochemical method. Electrodeposition experiments were performed from 0.005 M Ni(NO₃)₂ bath at a constant current density of 0.1 mA cm^?2 on the steel cathode for 1 h. Recording the potential values during the deposition process revealed that the reduction of water has major role in the base electrogeneration at the applied conditions. The obtained deposit was characterized by the X-ray diffraction (XRD), infrared (IR), differential scanning calorimeter–thermogravimetric analysis, carbon–nitrogen–hydrogen (CHN), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. The CHN, XRD, and IR analyses showed that the obtained deposit has α phase of Ni(OH)₂ with intercalated nitrate ions in its structure. Morphological characterization by SEM and TEM revealed that the prepared α-Ni(OH)₂ is composed of well-dispersed ultrafine particles with the size of about 5 nm. The supercapacitive performance of the prepared nanoparticles was analyzed by means of cyclic voltammetry and galvanostatic charge–discharge tests. The electrochemical measurements showed an excellent supercapacitive behavior of the prepared α-Ni(OH)₂ nanoparticles. It was also observed that the α-Ni(OH)₂ ultrafine particles have better electrochemical characteristic and supercapacitive behavior than β-Ni(OH)₂ ultrafine nanoparticles, including less positive charging potential, lower E _a???E _c value, better reversibility, higher E _OER???E _a, higher utilization of active material, higher proton diffusion coefficient, greater discharge capacity, and better cyclability. These results make the α-Ni(OH)₂ nanoparticles as an excellent candidate for the supercapacitor materials.     

A comparative DFT study of Fe3+ and Fe2+ ions adsorption on (100) and (110) surfaces of pyrite: An electrochemical point of view

Pyrite acts as a catalyst in the mineral processing, and the speed of ferric ion reduction and mineral decomposition increases with increasing cathodic points. In this study, the ferric ion interaction on the (100) and (110) surfaces of pyrite was studied using the density functional theory calculations. The analysis of stability, density of states, and electron density were performed to understand the interaction between the ferric ion and pyrite surfaces. The results showed that pyrite surface is chemically active and tends to absorb ferric ion between two surface sulfur atoms. The hyperconjugation between the 3d orbital of ferric ion and the 3p or 3d orbitals of surface atoms provides the conditions for the Fe³⁺ ion adsorption. The molecular orbital (MO) and electron density analyses indicate that the 3p orbitals of S atoms play a more important role in bonds formations relative to the 3d orbitals. The (110) surface is more active, and the adsorption energy is larger than that of surface (100), which is the result of decreased cation coordination and the presence of sulfur at the surface. Subsequently, the interaction of the Fe²⁺ ion, as product of Fe³⁺ ion reduction and its competitor for adsorption, on the surfaces was studied. The Fe^{2 +} ion adsorbs stronger at the surface of (110), and the adsorption energies at (100) and (110) surfaces were obtained as −24 and −47 kcal/mol, respectively. In general, the Fe³⁺ ion is a stronger oxidizing agent than Fe²⁺ on pyrite surfaces.     

Synthesis of a new series of pyrazolo[1,5‐a]pyrimidines structurally related to zaleplon

The reaction between 3‐(dimethylamino)/3,3‐bis(methylthio)‐1‐(substituted)prop‐2‐en‐1‐ones and 4‐substituted‐5‐amino‐1H‐pyrazoles afforded new pyrazole[1,5‐a]pyrimidines structurally related to Zaleplon. The chemical modifications introduced at the 3‐, 5‐, and 7‐positions of the bicyclic structure revealed new promising candidates for the treatment of sleep disorders.     

Nanostructure Copper-exchanged ZSM-5 Catalytic Activity for Conversion of Volatile Organic Compounds (Toluene and Ethyl Acetate)

Gas phase catalytic oxidation of ethyl acetate and toluene was examined over copper modified ZSM‐5 catalysts under atmospheric pressure. Nanostructure of ZSM‐5 was characterized by XRD, SEM and TEM techniques. Elemental composition of ZSM‐5 was determined using EDX, ICP‐AES and XPS techniques. Results of catalytic studies showed better catalytic activity of Cu‐ZSM‐5 catalysts than those of parent ZSM‐5 and HZSM‐5, which revealed catalytic role of copper ions in the Cu‐ZSM‐5 catalysts. Effects of some parameters over catalytic conversion of these compounds were also studied. Ethyl acetate showed more reactivity than toluene over the Cu‐ZSM‐5 catalysts. Furthermore, the catalytic activity of Cu‐ZSM‐5 catalysts increased with increasing the copper loadings. The conversion behavior of a binary mixture of ethyl acetate and toluene was different from that of a single form. A promotive and inhibitive behavior was observed for conversion of ethyl acetate and toluene in the binary mixture, respectively. Water vapor as co‐feed had an inhibitive effect on conversion of organic compounds over the Cu‐ZSM‐5 catalysts.     

Ligand recognition by SH3 and WW domains: the role of N-alkylation in PPII helices.

SH3 and WW domains are involved in a variety of intracellular signaling pathways. Recent work has shed light on the mechanism whereby these signaling modules recognize prolines in polyproline ligands, which has implications in the design of ligands selectively targeting these interactions.