Preparation and Characterization of Agarose-Gelatin Blend Hydrogels as a Cell Encapsulation Matrix: An In-Vitro Study

Cell encapsulation represents an alternative nonviral technique to treat multiple diseases, leading to a reduction or even absence of administration of immunosuppressants. Hydrogels have been introduced as novel materials suitable for cell encapsulation. This study involves agarose–gelatin blend hydrogels with four different weight percentage ratios (100:0, 75:25, 50:50, 25:75) of agarose to gelatin. Prepared blend hydrogels were assessed in terms of rheological behavior (gel point by using complex viscosity), cell attachment (hemocytometer), cell viability and cytotoxicity (3-(3,4-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliium bromide, MTT assay), and mechanical and integral stability (Bradford test and shear force rupture assay, respectively). Based on the obtained rheological experimental results, the sol-gel transition point for 50:50 was in the physiological condition range (35°C–37°C). The percent of nonattached cells on the surface of the hydrogel decreased from 92% for the 100:0 sample to 46.3% for the 50:50 sample, and the cell viability was more than 95%. A good structural integrity was achieved for samples with weight ratio of 50:50; 20.195% gelatin was released during the 24 h in phosphate buffer solution at 25°C and the mechanical stability of agarose–gelatin microcapsules under shear force were improved about 14% rather than pure agarose microcapsule.     

Altitude distribution of the auroral acceleration potential determined from cluster satellite data at different heights

Aurora, commonly seen in the polar sky, is a ubiquitous phenomenon occurring on Earth and other solar system planets. The colorful emissions are caused by electron beams hitting the upper atmosphere, after being accelerated by quasistatic electric fields at 1-2 R(E) altitudes, or by wave electric fields. Although aurora was studied by many past satellite missions, Cluster is the first to explore the auroral acceleration region with multiprobes. Here, Cluster data are used to determine the acceleration potential above the aurora and to address its stability in space and time. The derived potential comprises two upper, broad U-shaped potentials and a narrower S-shaped potential below, and is stable on a 5 min time scale. The scale size of the electric field relative to that of the current is shown to depend strongly on altitude within the acceleration region. To reveal these features was possible only by combining data from the two satellites.     

Numerical simulation of electric field in complex geometries for different electrode arrangements using meshless local MQ-DQ method

In this paper the meshless Local Multi Quadrics-based Differential Quadrature (MQ-DQ) method is applied to obtain the electric field distribution for different applicable irregular geometries. This method is the combination of Differential Quadrature approximation of derivatives and function approximation of MQ-Radial Basis Function (RBF). Three different geometries with irregular boundaries are considered and the obtained results are compared with those gained by Finite Element (FE) solutions achieved by COMSOL commercial code. Outcomes prove that current technique is in very good agreement with FEM and this fact that MQ-DQ method is an accurate and flexible method in solution of electrostatic equations.     

Green Oxidations. Manganese(II) Sulfate Aided Oxidations of Organic Compounds by Potassium Permanganate

Summary. The oxidation of arenes and sulfides by potassium permanganate was accomplished in good yields under solvent free and heterogeneous conditions when manganese(II) sulfate is used as a solid support. After extraction of the organic products, the inorganic products can be reoxidized to permanganate. This result is important because it provides an approach to oxidation reactions that is, in theory, infinitely sustainable.     

Modified Glaser Reaction of Terminal Alkynes on KF/Alumina

Summary. A variety of 1,3-diyne compounds are prepared in a solvent-free reaction on KF/alumina in the presence of catalytic amounts of Cu(OAc)₂·H₂O with up to 96% yields at room temperature.     

Synthesis of methylene- and difluoromethylenephosphonate analogues of uridine-4-phosphate and 3-deazauridine-4-phosphate

Cytidine triphosphate synthetase (CTPS) catalyzes the formation of cytidine triphosphate from glutamine, uridine-5'-triphosphate (UTP), and adenosine-5'-triphosphate. Inhibitors of CTPS are of interest because of their potential as therapeutic agents. One approach to potent enzyme inhibitors is to use analogues of high energy intermediates formed during the reaction. The CTPS reaction proceeds via the high energy intermediate UTP-4-phosphate (UTP-4-P). Four novel analogues of uridine-4-phosphate (U-4-P) and 3-deazauridine-4-phosphate (3-deazaU-4-P) were synthesized in which the labile phosphate ester oxygen was replaced with a methylene and difluoromethylene group. The methylene analogue of U-4-P, compound 1, was prepared by a reaction of the sodium salt of tert-butyl diethylphosphonoacetate with protected, 4-O-activated uridine followed by acetate deprotection and decarboxylation. It was found that this compound undergoes relatively facile dephosphonylation presumably via a metaphosphate intermediate. The difluoromethylene derivative, compound 2, was prepared by electrophilic fluorination of protected 1. This compound was stable and did not undergo dephosphonylation. Synthesis of the methylene analogue of 3-deazaU-4-P, compound 3, was achieved by ribosylation of protected 4-(phosphonomethyl)-2-hydroxypyridine. Electrophilic fluorination was also employed in the preparation of protected 4-(phosphonodifluoromethyl)-2-hydroxypyridine which was used as the key building block in the synthesis of difluoro derivative 4. These compounds represent the first examples of a nucleoside in which the base has been chemically modified with a methylene or difluormethylenephosphonate group.     

Ionic liquid-mediated Darzens condensation: An environmentally-friendly procedure for the room-temperature synthesis of α,β-epoxy ketones

This room-temperature Darzens condensation of α-chloroacetophenone with various aromatic aldehydes mediated by [bmim][BF₄] ionic liquid in the presence of sodium tert-butoxide resulted in the sole formation of good to excellent yields of trans-α,β-epoxy ketones in short time periods. In contrast, tert-butyl 2-chloroacetate underwent Darzens reactions with aldehydes giving mixtures of both cis and trans products with low selectivity. In all reactions, the ionic liquid was recovered and reused in the subsequent reactions without significant loss of activity.