Novel modified nanoporous silica for oral drug delivery: loading and release of clarithromycin

Nanoporous silica SBA-15 was prepared to evaluate its application as an oral drug delivery system. A series of surface-functionalized nanopore materials as efficient clarithromycin delivery carriers was investigated. An efficient pH-responsive carrier system was constructed by hydrogen bond interaction between carboxyl and hydroxyl groups in the clarithromycin and the amine group in modified SBA-15. HPLC analyses of clarithromycin were run on a C₁₈ column using a mobile phase comprised of potassium dihydrogen phosphate, acetonitrile and methanol (30:40:30, v/v/v). Active molecules such as clarithromycin could be stored and released from the pore voids of SBA-15 by changing the pH. The amount of clarithromycin stored in the pores of nanoporous silica based on TREN [tris(2-aminoethyl) amine]-modified SBA-15 rods was up to 46 ± 4.8 wt% at pH 8. In addition, when the pH was below 4, clarithromycin was steadily released from the pores of SBA-15 (up to 97 wt% in simulated gastric medium).     

甲烷氧化偶联锂/氧化镁催化剂和纳米催化剂

The Li/MgO catalyst and nanocatalyst were prepared by the incipient wetness impregnation and sol-gel method, respectively. The catalytic performance of the Li/MgO catalyst and nanocatalyst on oxidative coupling of methane was compared. The catalysts prepared in two ways were characterized by X-ray powder diffraction, Brunauer-Emmett-Teller surface and transmission electron microscope. The catalyst was tested at temperature of 973-1073 K with constant total pressure of 101 kPa. Experimental results showed that Li/MgO nanocatalyst in the oxidative coupling of methane would result in higher conversion of methane, higher selectivity, and higher yield of main products (ethane and ethylene) compared to ordinary catalyst. The results show the improved influence of nanoscale Li/MgO catalyst performance on oxidative coupling of methane.     

Electrocatalytic determination of sulfite using a modified carbon nanotubes paste electrode: application for determination of sulfite in real samples

This paper introduces a carbon paste electrode modified with ferrocene and carbon nanotubes as a voltammetric sensor for determination of sulfite at pH 7.0. The results showed that under the optimum condition (pH 7.0) in cyclic voltammetry, the oxidation of sulfite occurred at a potential about 280?mV less positive than the unmodified carbon paste electrode. Kinetic parameters such as electron transfer coefficient (??) and heterogeneous rate constant (k) for sulfite were also determined using electrochemical approaches. Under the optimized conditions, the electrocatalytic oxidation peak current of sulfite showed two linear dynamic ranges with a detection limit of 0.1???M for sulfite. The proposed method was examined as a selective, simple, and precise method for voltammetric determination of sulfite in some real samples such as weak liquor from wood and paper industry, boiler water, river water, industrial water, and tap water.     

Synthesis,characterization, crystal structure determination and computational study of the high-spin iron(II) 2-cyanopyrazine complex trans-[Fe(pzCN)4Cl2]

A new mononuclear high-spin complex, trans-[Fe(pzCN)₄Cl₂] (1), was prepared from the reaction of FeCl₂.4H₂O and 2-cyanopyrazine (pzCN) in acetonitrile as a solvent. Suitable crystals of this complex for crystal structure determination were collected by slow evaporation of the produced pale orange solution. Complex 1 was characterized by elemental analysis (CHN), spectral methods (IR and UV–Vis), and single-crystal X-ray diffraction. The X-ray structural analysis indicated that the iron(II) is six-coordinated in an octahedral configuration by four N atoms from four 2-cyanopyrazine ligands and two chloride anions. Furthermore, the average of Fe–N bond lengths is 2.284(1)Å. It is well known that in the high-spin iron(II) phenanthroline and bipyridine complexes, the Fe–N bond lengths are around 2.2 Å. So, due to the Fe–N bond length in this complex, the iron(II) is unambiguously high-spin. The experimental evaluations on 1 have been complemented theoretically by the density functional theory (DFT) and TD-DFT calculations. The character of the Fe–N and Fe–Cl bonds was investigated using quantum theory of atoms in molecules. Additionally, electron delocalization and hyper-conjugative interactions of the synthesized complex were evaluated by natural bond orbital calculations.

     

Correction to: A comprehensive review on radioactive waste cycle from generation to disposal

Journal of Radioanalytical and Nuclear Chemistry - A correction to this paper has been published: https://doi.org/10.1007/s10967-021-07815-8     

A new monitor model to detect damages in surface and subsurface during cup grinding process of BK7 optical glass: a new optimization model for energy damage

Journal of Thermal Analysis and Calorimetry - Grinding is known as the most widely used method of forming borosilicate optical glass (BK7). Due to the brittle nature of the BK7 glass, the...     

Estimation of mechanical properties of LDPE/LLDPE/SEBS nanocomposite reinforced with calcium carbonate nanoparticles by Ch mathematical model

Journal of Thermal Analysis and Calorimetry - Doing experiments in order to determine mechanical properties of nanocomposites costs a lot. Therefore, finding the ways by which the properties of the...     

MicroRNA‐2861 and nanofibrous scaffold synergistically promote human induced pluripotent stem cells osteogenic differentiation

Tissue engineering using new strategies has become a growing and promising method for treating large tissue lesions in the body. On the other hand, microRNAs (miRNAs), which are small non‐coding regulatory RNAs, are a new class of genetic materials that can have effective pharmacological roles. The combination of these two themes has created promising prospects for the treatment of diseases. Herein, human induced pluripotent stem cells (iPSCs) were transduced with miRNA‐2861 and then the osteogenic differentiation potential of transduced iPSCs and non‐transduced iPSCs was investigated while cultured on the electrospun poly lactic‐co‐glycolic acid (PLGA) nanofibrous scaffold and culture plate. MiR‐2861‐transduced iPSCs showed a significantly higher viability, mineralization, alkaline phosphatase (ALP) activity, calcium content, and bone‐related gene expression in comparison with those iPSCs that non‐transduced. The results also indicated that this increase is improved when miR‐2861 transduced iPSCs are cultured on the PLGA nanofibrous scaffold synergistically. This synergy was also confirmed by the results obtained from of Western blot analysis. It can be concluded that, miR‐2861, by negative regulation of those proteins that decrease/inhibit osteogenic differentiation and PLGA nanofibrous scaffold by preparation of a suitable artificial extracellular matrix, have a great positive impact in improving iPSCs osteogenic differentiation potential and this blend can be proposed to use in bone tissue engineering application.     

Dynamic analysis of a novel wide-tunable microbeam resonator with a sliding free-of-charge electrode

In this paper, a MEMS-based resonator with a novel effective stiffness tunability is presented. The performance of the proposed resonator is based on the transversal vibration of the two porous cantilever microbeams with a rectangular microplate at the end of the structure. The microplate as a free-of-charge slider electrode is in contact with two other fixed substrate electrodes via the thin layer of dielectric material. Applying a constant DC voltage to the two fixed electrodes leads to the movement of free electrons in the slider and eventually to the formation of two series capacitors. As a result, the slider meets a nonlinear electrostatic force proportional to the square of the applied DC voltage. It will act as a nonlinear spring with a tunable stiffness during the oscillation of the resonator. The coupled nonlinear equations governing the longitudinal and transversal vibration of the resonator are extracted in the presence of the nonlinear voltage-sliding spring. Its steady-state solution is obtained based on a physically based learning method that makes it possible to obtain frequency response for the first harmony as well as for the higher harmonies and to predict primary and secondary resonances in different harmonies of the response. The effect of the applied tuning DC voltage, the geometrical parameters of the resonator, and the cantilever's porosity on the dynamic response of the resonator are investigated. It is shown that the tuning stiffness of this voltage-sliding spring provides a highly effective solution to realize an extreme tunable range. In the end, a modified tunable structure is introduced in which the folded beams are replaced with common ones. The modified resonator by making the nonlinear behavior of the resonator least can improve its performance significantly.

     

Monomer and cyclic tetramer of copper(II) complexes: Synthesis,characterization and crystal structure determination of [Cu(dm4bt)Cl(Hipht)] and [{Cu(dm4bt)(H2O)(ipht)}4·2H2O]

Copper complexes, [Cu(dm4bt)Cl(Hipht)] (1) and [{Cu(dm4bt)(H₂O)(ipht)}₄·2H₂O] (2) (where dm4bt is 2,2′-dimethyl-4,4′-bithiazole, Hipht is hydrogen isophthalate and ipht is isophthalate) have been synthesized. These two complexes were characterized by IR, UV–Vis and EPR spectroscopy. Moreover; their single-crystal structures were studied by the X-ray diffraction method. Complex 1 has a monomer structure and copper has accepted a distorted square pyramidal structure. Isophthalic acid in 1 lost one of its protons and produced one bidentate carboxylate and one free carboxylic acid. Controlled deprotonation in the presence of ethylene diamine results in self-assemblies of 1 to form a tetramer complex of 2. Complex 2 has two kinds of spatial isomers which are resolved by EPR and X-ray.