Silica-coated manganite and Mn-based ferrite nanoparticles: a comparative study focused on cytotoxicity

Magnetic oxide nanoparticles provide a fascinating tool for biological research and medicine, serving as contrast agents, magnetic carriers, and core materials of theranostic systems. Although the applications rely mostly on iron oxides, more complex oxides such as perovskite manganites may provide a much better magnetic performance. To assess the risk of their potential use, in vitro toxicity of manganite nanoparticles was thoroughly analysed and compared with another prospective system of Mn–Zn ferrite nanoparticles. Magnetic nanoparticles of La_0.63Sr_0.37MnO₃ manganite were prepared by two distinct methods, namely the molten salt synthesis and the traditional sol–gel route, whereas nanoparticles of Mn_0.61Zn_0.42Fe_1.97O₄ ferrite, selected as a comparative material, were synthesized by a new procedure under hydrothermal conditions. Magnetic cores were coated with silica and, moreover, several samples of manganite nanoparticles with different thicknesses of silica shell were prepared. The size-fractionated and purified products were analysed using transmission electron microscopy, dynamic light scattering, measurement of the zeta-potential dependence on pH, IR spectroscopy, and SQUID magnetometry. The silica-coated products with accurately determined concentration by atomic absorption spectroscopy were subjected to a robust evaluation of their cytotoxicity by four different methods, including detailed analysis of the concentration dependence of toxicity, analysis of apoptosis, and experiments on three different cell lines. The results, comparing two manganese-containing systems, clearly indicated superior properties of the Mn–Zn ferrite, whose silica-coated nanoparticles show very limited toxic effects and thus constitute a promising material for bioapplications.     

Thermal quantum time-correlation functions from classical-like dynamics

Thermal quantum time-correlation functions are of fundamental importance in quantum dynamics, allowing experimentally measurable properties such as reaction rates, diffusion constants and vibrational spectra to be computed from first principles. Since the exact quantum solution scales exponentially with system size, there has been considerable effort in formulating reliable linear-scaling methods involving exact quantum statistics and approximate quantum dynamics modelled with classical-like trajectories. Here, we review recent progress in the field with the development of methods including centroid molecular dynamics , ring polymer molecular dynamics (RPMD) and thermostatted RPMD (TRPMD). We show how these methods have recently been obtained from ‘Matsubara dynamics’, a form of semiclassical dynamics which conserves the quantum Boltzmann distribution. We also apply the Matsubara formalism to reaction rate theory, rederiving t → 0₊ quantum transition-state theory (QTST) and showing that Matsubara-TST, like RPMD-TST, is equivalent to QTST. We end by surveying areas for future progress.     

Hydroxylation of nitro-(pentafluorosulfanyl)benzenes via vicarious nucleophilic substitution of hydrogen

Para- and meta-nitro-(pentafluorosulfanyl)benzenes react with anions of cumyl hydroperoxide in the presence of t-BuOK in liquid ammonia to form nitro-(pentafluorosulfanyl)phenols. Their reduction with hydrogen in the presence of Raney-Nickel provides amino-(pentafluorosulfanyl)phenols.     

Comparison of LC Columns Packed with 2.6?��m Core-Shell and Sub-2?��m Porous Particles for Gradient Separation of Antibiotics

The recently introduced Kinetex C18 column packed with core-shell 2.6 ??m particles is declared to provide similar efficiency and short analysis as Acquity BEH C18 column with 1.7 ??m porous particles. Unlike Acquity BEH C18 column, Kinetex C18 column exhibited lower column backpressure making this column compatible to conventional LC systems. The performance of Kinetex C18 column (2.1 × 50 mm) and Acquity BEH C18 column (2.1 × 50 mm) for gradient separation of tetracyclines under acidic conditions (oxytetracycline, tetracycline, chlortetracycline, and doxycycline) and macrolides under alkaline conditions (tylosin, clarithromycin, roxithromycin, and carbomycin) was studied. The columns were compared by evaluation of their experimental peak capacity and its dependence on linear velocity and gradient slope. The maximal experimental peak capacities for analysis of tetracyclines were 51.8 (Acquity BEH C18 column) and 48.4 (Kinetex C18 column). This indicated that Kinetex C18 was a suitable alternative to Acquity BEH C18 column for the analysis of tetracyclines under acidic conditions. On the contrary, the maximal experimental peak capacities for analysis of macrolides on Acquity BEH C18 column was higher (46.7) than that on Kinetex C18 column (36.9). Moreover, application of Kinetex C18 column for the analysis of macrolides under alkaline conditions was limited with respect to its decreasing performance with growing number of injections on the column.     

Simple,Multicomponent, Ecofriendly,Microwave-Mediated Route for the Synthesis of Antimicrobial 2-Amino-6-aryl-4-(3H)-pyrimidinones

In this work, we describe a multicomponent microwave-mediated synthesis of 10 2-amino-6-aryl-4-oxo-1,6-dihydro-pyrimidine-5-carbonitriles in good chemical yields (44–67%), four of them not related in earlier literature. All pyrimidinones synthesized herein had their antimicrobial activity evaluated against the following microorganisms: Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. Two of the synthesized substances displayed good antimicrobial activity against P. aeruginosa and S. aureus, two bacteria responsible for nosocomial infections.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]     

Synthesis of Mesoionic 4‐(para‐substituted Phenyl‐5‐2,4‐dichlorophenyl)‐1,3‐4‐thiadiazolium‐2‐aminides by Direct Cyclization via Acylation of Thiosemicarbazides

The synthesis of ten novel mesoionic 4‐[para‐substituted (H, CH₃, OCH₃, NO₂, Cl, Br, OH, t‐C₄H₉, C₆H₅, C₄H₉) phenyl‐5‐2,4‐dichlorophenyl]‐1,3‐4‐thiadiazolium‐2‐aminides, as hydrochlorides, are described. The synthesis strategy utilized the corresponding para‐substituted isothiocyanates as starting materials to obtain the thiosemicarbazides through reaction with phenylhydrazine (61–98%), which were then submitted to acylation with 2,4‐dichloro benzoyl chloride and direct cyclization to generate the desired substituted mesoionic compounds in good yields (ca. 80%).