GC–MS method for the determination of paraben preservatives in the human breast cancerous tissue

The general presumption that the preservative laden personal care products may be one of the causative agents for breast cancer, has remained a matter of controversy during this decade. Extensive studies have not been carried out to either prove or disprove the role of preservatives in breast cancer incidences. In this study we have developed a new method for the identification and quantification of the preservatives such as methyl paraben (MeP), ethyl paraben (EtP), propyl paraben (PrP) and butyl paraben (BuP) in breast tissue using Gas Chromatography and Mass Spectrometry (GC–MS). Tissue was extracted by using acetone:n-hexane mixture (1:1 v/v) and derivatized with N-Methyl-N-(trimethylsilyl) trifluoroacetamide (MSTFA). The extent of reaction time and the amount of MSTFA to attain greater derivatization were optimized. The developed method yielded good recovery (mean ± SD) of 99.8 ± 5.1, 96 ± 4.4, 107 ± 17 and 113 ± 13% with relative standard deviations (RSDs) of 5.1, 4.6, 15.6 and 13%, and the limits of detection (LOD) of 2.02, 1.05, 1.71 and 3.75 ng g^{− 1} for MeP, EtP, PrP and BuP, respectively. The method was successfully validated for the determination of parabens including butyl paraben (log K_ow = 3.57) in cancerous breast tissues; this could be a promising one for screening of breast tissues and also the environment for paraben residues. As far as our knowledge goes this is the first GC–MS method for the determination of parabens in human tissue.     

Single-particle trajectories in a cusped magnetic field

The trajectories of a single charged particle in relation to the cusp axis and cusp plane in a cusped magnetic field are numerically studied. The results show that the particle reflected by the cusp field forms a double helix; i.e., the helix itself makes a helical motion. The location of the reflection point extends well into the injection side of the cusp plane, suggesting that a diverging magnetic field of appropriate geometry may be able to reflect a charged particle. However, the location of the reflection point does not alter the nature of the trajectory     

Photo-cross-linking-assisted thermal stability of DNA origami structures and its application for higher-temperature self-assembly

Heat tolerance of DNA origami structures has been improved about 30 °C by photo-cross-linking of 8-methoxypsoralen. To demonstrate one of its applications, the cross-linked origami were used for higher-temperature self-assembly, which markedly increased the yield of the assembled product when compared to the self-assembly of non-cross-linked origami at lower-temperature. By contrast, at higher-temperature annealing, native non-cross-linked tiles did not self-assemble to yield the desired product; however, they formed a nonspecific broken structure.     

Analytical expression of non steady-state concentration for the CE mechanism at a planar electrode

The analytical solutions of the non-steady-state concentrations of species at a planar microelectrode are discussed. The analytical expression of the kinetics of CE mechanism under first or pseudo-first order conditions with equal diffusion coefficients at planar electrode under non-steady-state conditions are obtained by using Homotopy perturbation method. These simple new approximate expressions are valid for all values of time and possible values of rate constants. Analytical equations are given to describe the current when the homogeneous equilibrium position lies heavily in favour of the electroinactive species. Working surfaces are presented for the variation of limiting current with a homogeneous kinetic parameter and equilibrium constant. In this work we employ the Homotopy perturbation method to solve the boundary value problem. Furthermore, in this work the numerical simulation of the problem is also reported using Scilab program. The analytical results are found to be in excellent agreement with the numerical results.     

Cell-penetrating peptides as delivery vehicles for a protein-targeted terbium complex

Release after transmission: Arginine-rich, cell-penetrating peptides (CPPs) mediate cytoplasmic delivery of trimethoprim (TMP)-terbium complex conjugates and selective, intracellular labeling of E.?coli dihydrofolate reductase (eDHFR) fusion proteins. A disulfide bond linking CPP and cargo is reduced following uptake. CPP conjugation can be used to deliver otherwise cell-impermeable, ligand-fluorophore conjugates.     

Electrochemical plasmonic sensors

The enormous progress of nanotechnology during the last decade has made it possible to fabricate a great variety of nanostructures. On the nanoscale, metals exhibit special electrical and optical properties, which can be utilized for novel applications. In particular, plasmonic sensors including both the established technique of surface plasmon resonance and more recent nanoplasmonic sensors, have recently attracted much attention. However, some of the simplest and most successful sensors, such as the glucose biosensor, are based on electrical readout. In this review we describe the implementation of electrochemistry with plasmonic nanostructures for combined electrical and optical signal transduction. We highlight results from different types of metallic nanostructures such as nanoparticles, nanowires, nanoholes or simply films of nanoscale thickness. We briefly give an overview of their optical properties and discuss implementation of electrochemical methods. In particular, we review studies on how electrochemical potentials influence the plasmon resonances in different nanostructures, as this type of fundamental understanding is necessary for successful combination of the methods. Although several combined platforms exist, many are not yet in use as sensors partly because of the complicated effects from electrochemical potentials on plasmon resonances. Yet, there are clearly promising aspects of these sensor combinations and we conclude this review by discussing the advantages of synchronized electrical and optical readout, illustrating the versatility of these technologies.     

Analysis of plasticizer influence in Poly(vinyl acetate)/Poly(vinylidene fluoride) polymer blend electrolyte

Gel polymer electrolyte based on poly(vinyl acetate) and poly(vinylidene fluoride) was prepared by solvent casting technique, in which the addition of plasticizers improves the conductivity of polymer membranes. The blend polymer electrolyte containing propylene carbonate (PC) exhibits the highest conductivity of 0.922?×?10^?2 S cm^?1 at room temperature because of the higher dielectric constant as compared to other plasticizers used in the present study. Material characterizations were done with the help of SEM and FT-IR techniques. The activation energy values were computed from ‘log σ?1/T’ Arrhenius plots.     

Anti-Osteoporotic activity of metal complexes of amine carboxyboranes

Metal complexes of trimethylamine carboxyborane successfully suppressed calcium flux from both paired pup calvaria bones and rat UMR-106 osteosarcoma cultured cells over a 48 h period. These agents increased uptake of calcium into the cell cultures and accelerated [³H]proline incorporation into collagen. Copper and iron complexes of the trimethylamine carboxyborane were more potent compared with the cobalt and chromium complexes. The agents effectively reduced Iysosomal enzyme activity and also proteolytic enzyme activities of macrophages. Since macrophages invade the bone surface and assist in the demineralization and digestion of collagen, those agents may be potentially useful to retard diseases involving bone reconstruction. Influx of white blood cells and macrophages to sites of degradation most probably would be inhibited by the agents, based on sponge test observations in mice. Osteoporosis induced by ovariectomy was minimized by injections of tetrakis[u-(trimethylamine-boranecarboxylato)-bis(trimethylamine-carboxyborane)dicopper(II)] into rats at 3.5 mg kg^?1 day^?1 for 14 days. Bone volume, density, weight and calcium content returned to normal baseline control values. In addition, the copper complex returned serum calcium, serum parathyroid hormone (PTH) and vitamin D₃ values to normal levels. One possible mode of action of these derivatives is the regulation of the production and release of chemical mediators initiating bone loss, e.g. tumor necrosis factor, TNF α and interleukins 11 or 11-2.     

Kinetic studies on light-induced cationic ring-opening reactions on 2,3-epoxypropyl phenyl ether

Light-induced cationic ring-opening reactions of 2,3-epoxypropyl phenyl ether (phenyl glycidyl ether, PGE) in acetone, methanol and bulk were studied. Cations are produced by electron transfer from excited sensitizers (anthracene, An; 9,10-phenanthrenequinone, PQ; benzophenone, BP) or from photolytically cleaved sensitizer (benzoin isoproyl ether, BIPE) to diphenyliodonium hexafluorophosphate. With excess of acetone and methanol, addition reactions take place resulting in 2,2-dimethyl-4-phenoxymethyl-1,3-dioxolane and 1-methoxy-3-phenoxy propan-2-ol as main products. The efficiency of the sensitizers taken from the quantum yields of PGE conversion, follows the order An ? BIPE > PQ > BP in acetone and An ～ BP > BIPE ? PQ in methanol. Unlike bulk polymerization, in these addition reactions no steady-state concentration of cations exists and the reaction accelerates with time. When alcohol is added in only small proportions, the initial addition reactions goes over into a linear oligomerization. The relatively higher basicity of methanol over PGE influences the nature of the active center, and the course of reaction depends on methanol concentration. Kinetic expressions, which account for all possible types of active centers, have been derived to express the rate of PGE reactions in methanol.