In vitro surface biocompatibility of high-content silicon-substituted calcium phosphate ceramics

The present work investigates surface biocompatibility of silicon-substituted calcium phosphate ceramics. Different silicon-substituted calcium phosphate ceramic bodies were prepared from co-precipitated powders by sintering at 1300°C. The in vitro bioactivity of the ceramics was assessed in simulated body fluid (SBF) at 37°C for periods up to 4 weeks. The changes in the surface morphology and composition were determined by scanning electron microscopy (SEM) coupled with electron probe microanalysis and energy dispersive spectrometer (EDX). Inductively coupled plasma optical emission spectroscopy (ICP-OES) was used to observe the change in ionic concentration of SBF after removal of the samples. The bioactivity of the ceramics increased with an increasing silicate ion substitution in a systematic way. The surface of ceramics with 2.23% silicon substitution was partially covered with apatite layer after one week, while ceramics with 8.1% silicon substitution were completely covered with apatite in the first week. The porous microstructure of high-concentration Si-substituted ceramics helps the dissolution of surface ions and the leaching process. This allows SBF to reach supersaturation in a short time and accelerate the deposition of apatite layer.      

Novel Pyrano[2,3‐d]thiazole and Thiazolo[4,5‐b]pyridine Derivatives: One‐pot Three‐component Synthesis and Biological Evaluation as Anticancer Agents,c‐Met,and Pim‐1 Kinase Inhibitors

Preparation of pyrano[2,3‐d]thiazole and thiazolo[4,5‐b]pyridine derivatives through multicomponent reactions (MCRs) was achieved by the reaction of 2‐(2‐amino‐4,5,6,7‐tetrahydrobenzo[b]thiophen‐3‐yl)thiazol‐4(5H)‐one with various active methylene reagents such as ethyl cyanoacetate or malononitrile in basic conditions containing diverse aromatic aldehyde. Furthermore, this study aims to evaluate the in vitro cytotoxic activity of the synthetic compounds against six cancer cell lines, and all the prepared compounds revealed valuable activity compared with the CHS‐828, which is the 2‐[6‐(4‐chlorophenoxy)hexyl]‐1‐cyano‐3‐pyridin‐4‐ylguanidine as the standard drug. Some of the pyrano[2,3‐d]thiazole and thiazolo[4,5‐b]pyridine derivatives showed the highest antitumor activity towards the six cancer cell lines. Moreover, (c‐Met) enzymatic activity of the most potent compounds showed that compounds 3b 2‐(2‐amino‐4,5,6,7 tetrahydrobenzo[b]thiophen‐3‐yl)‐5‐hydroxy‐7‐(2‐hydroxy‐phenyl)‐7H‐pyrano[2,3‐d]thiazole‐6 carbonitrile and 5e 2‐(2‐amino‐4,5,6,7‐tetrahydrobenzo[b]thiophen‐3‐yl)‐5‐hydroxy‐7‐phenyl‐4,7‐dihydrothiazolo[4,5‐b]pyridine‐6‐carbonitrile were with higher activities than foretinib. Three compounds were selected to examine their Pim‐1 kinase where compounds 3b and 7b showed the highest inhibitions.     

Heterogeneous catalytic oxidation of chromotrope 2B with H2O2 and metal complexes supported on aluminum oxide hydroxide as catalyst

The heterogeneous catalytic oxidation of Chromotrope 2B (C2B) dye with H₂O₂ and the aluminum oxide hydroxide (AlOOH) modified with ammonia complexes of Cu^II, Co^II, Ni^II, and Cr^III (AlOOH/[Mⁿ⁺(amm)_m]) as catalysts were studied. The AlOOH/[Cu^II(amm)₄] is the most efficient catalyst and therefore it was chosen as the potential catalyst for the oxidative degradation of C2B in an aqueous solution. The AlOOH/[Cu^II(amm)₄] was characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), and transmission electron microscopy (TEM), techniques. The rate of reaction was dependent on the type of the metal complex supported on the AlOOH, initial concentration of the dye and H₂O₂, catalyst dose, pH, the concentration of NaCl, and temperature. The catalytic activity of the AlOOH/[Mⁿ⁺(amm)_m] according to the kind of metal ion decreased in the order: Cu^II > Co^II > Cr^III > Ni^II. Other catalysts consisting of the AlOOH supported with Cu^II complexed with ethylenediamine, ethanolamine, 1,3 propanediamine, and 1,4 butanediamine, (AlOOH/[Cu^II(amine)_m]), were also investigated. The activity of the (AlOOH/[Cu^II(amine)_m]) as catalyst according to the type of ligand followed the order: 1,4 butanediamine > 1,3 propanediamine > ethanolamine > ethylenediamine > ammonia. The reaction rate increased with increasing the catalyst dose, concentration of H₂O_2, C2B, and NaCl, pH, and temperature. Since the reusability results for the AlOOH/[Cu^II(amm)₄] revealed good stability over seven cycles, it can thus be considered a promising and cost-effective catalyst for the removal of harmful dyes from wastewater.     

An eco-friendly multi-analyte high-performance thin layer chromatographic densitometric determination of amoxicillin,metronidazole, and famotidine in their ternary mixtures and simulated gastric juice: A promising protocol for eradicating Helicobacter pylori

Gastrointestinal tract disorders constitute a heavy burden to healthcare providers. To eradicate Helicobacter pylori infection, different triple therapy protocols have been proposed. Among which are combinations of proton pump inhibitors (e.g., omeprazole), histamine-2 receptor antagonists (e.g., famotidine), along with antibiotics (e.g., amoxicillin). In this work, a sensitive and accurate high-performance thin-layer chromatographic method was developed for the simultaneous determination of amoxicillin, metronidazole, and famotidine in bulk powder and laboratory-prepared combined-tablet mixtures. Complete separation of the cited compounds was achieved using pre-coated silica gel plates with a mixture of methanol:chloroform:toluene:water:glacial acetic acid (5:2:1.5:0.5:0.1 v/v/v/v/v) as the mobile phase. The method was fully validated as per the international conference of harmonization guidelines. Good linearity, a correlation coefficient of 0.9991, was obtained in the concentration ranges 0.1–1.6 μg/band (amoxicillin), 0.1–0.9 μg/band (metronidazole), and 0.1–0.9 μg/band (famotidine). Since the method allowed the determination of the three compounds in combined tablets with a high degree of selectivity, accuracy, precision, with cost-effectiveness, it could be used for regular quality control. Moreover, the applicability of the proposed method was extended to the determination of the ternary mixture in simulated gastric juice. Method greenness was assessed using different green metrics.     

Comparative study between two fabricated potentiometric sensors to enhance selectivity towards ferrous ions

Electroanalytical methods are highly selective for measuring electrical quantities including the charge, potential and current with their relation to chemical parameters. They are widely applied in various fields such as biochemical analysis, industrial quality control and environmental monitoring. They have many advantages over other techniques in that they are not time consuming and are specific for certain oxidation states of certain elements which give these techniques high selectivity and sensitivity features. This paper is based on two parts: the first part describes the fabrication of screen‐printed electrodes (SPEs) modified with methyl red as electroactive material, while second part describes the preparation and characterization of Fe(II)–methyl red complex using various spectroscopic tools, the complex being used for the construction of carbon paste electrodes (CPEs). The two proposed electrodes were successfully applied for the determination of Fe(II) in water and pharmaceutical (pharovit) samples. The electrodes under investigation show potentiometric response for Fe(II) in the concentration range 8.0 × 10^?7–1.0 × 10^?2 and 5.0 × 10^?7–1.0 × 10^?2 M at 25°C for SPE and CPE, respectively, and the electrode response is independent of pH in the range 1.5–7.0. These sensors show Nernstian slopes of 29.1 ± 0.2 and 29.7 ± 0.16 mV decade^?1 with detection limit values of 8.0 × 10^?7 and 5.0 × 10^?7 M for SPE and CPE, respectively. These electrodes show fast response time of 6 and 4 s and exhibit a lifetime of 100 and 30 days for SPE and CPE, respectively. The mechanism of chemical reaction between modifier and Fe(II) on the SPE surface was studied using infrared spectra, scanning electron microscopy and energy‐dispersive X‐ray analysis. The proposed potentiometric method was validated according to the IUPAC recommendations. The results obtained using the proposed sensors were comparable with those obtained with inductively coupled plasma analysis.     

A comparative study of HPLC-UV and UPLC-DAD methods for simultaneous estimation of aspirin and cilostazol in the presence of their related impurities in bulk and capsules

Aspirin (ASP) and cilostazol (CST) are used as a combination in pharmaceutical formulations for treatment of strokes. Salicylic acid (SAL) is considered to be one of the main synthesis impurities and a degradation product of ASP. On the other hand, the main related impurities of CST are CST related A, B, and C (CST-RA, CST-RB, and CST-RC), respectively. Furthermore, as high efficiency and less elution are the basic requirements of high-speed chromatographic separation, so, a comparative study of two simple, precise, and accurate reversed-phase HPLC and UPLC methods was developed and validated for simultaneous estimation of ASP and CST in bulk and capsules in the presence of SAL, CST-RA, CST-RB, and CST-RC. A Eurospher II C18 (250?×?4.6?mm², 5?µm) for HPLC method and an Agilent Zorbax Eclipse Plus C18 (50?×?2.1?mm², 1.8?µm) for UPLC method were used. A gradient mobile phase of 20?mM anhydrous KH₂PO₄ buffer solution (containing 0.2% triethylamine (TEA), v/v) with pH adjusted to 2.9 using orthophosphoric acid (solution A) and acetonitrile (solution B) mixed in different proportions for HPLC and UPLC methods was prepared. Flow rate was set to 1.0 and 0.3?mL min^?1 for HPLC and UPLC methods, respectively, and the detection was performed for both methods at 210?nm. It worth noting that the proposed UPLC-DAD assay exhibited relatively much more precision, sensitivity, specificity, and economic and chromatographic separation superiority than proposed HPLC-UV assay. Both developed methods were compared with reference methods to prove its applicability and are suitable for purity assessment of ASP and CST in bulk and capsules.     

Simultaneous Spectrophotometric Determination of Imipramine Hydrochloride with Chlordiazepoxide and Nortriptyline Hydrochloride with Fluphenazine Hydrochloride

Spectrophotometry was used with multivariate calibration to simultaneously determine compounds in mixtures. Two antidepressant mixtures were investigated: imipramine hydrochloride and chlordiazepoxide and nortriptyline hydrochloride and fluphenazine hydrochloride. Considerable spectral overlap and large differences in component concentrations were challenges. Since this type of analysis is often performed using complex algorithms, a simple strategy was used here for the simultaneous determination of both mixture components by classical least squares, principal component regression, and partial least squares. Experimental design was used to select the optimum parameters including the wavelength range, sampling interval, software, and derivative order. Accuracy was enhanced by proper wavelength selection. In addition, derivatives of the raw spectra improved the selectivity. The standard deviation, deviation of mean recovery from 100%, and prediction ability of the models were used as the responses. In respect to these terms, first-order derivatization of the spectra and a sampling interval of 1?nm provided the best results. In particular, the low concentration compounds in the mixtures (chlordiazepoxide and fluphenazine) were determined more accurately with precision lower than 3%. The strategy was used for the quality control of pharmaceuticals containing the mixtures without chemical pretreatment.     

The embedding conjecture for quasi-ordinary hypersurfaces

This paper has two objectives: we first generalize the theory of Abhyankar-Moh to quasi-ordinary polynomials, then we use the notion of approximate roots and that of generalized Newton polygons in order to prove the embedding conjecture for this class of polynomials. This conjecture-made by S.S. Abhyankar and A. Sathaye-says that if a hypersurface of the affine space is isomorphic to a coordinate, then it is equivalent to it.