Localized electric field induced transition and miniaturization of two‐phase flow patterns inside microchannels

Strategic application of external electrostatic field on a pressure‐driven two‐phase flow inside a microchannel can transform the stratified or slug flow patterns into droplets. The localized electrohydrodynamic stress at the interface of the immiscible liquids can engender a liquid‐dielectrophoretic deformation, which disrupts the balance of the viscous, capillary, and inertial forces of a pressure‐driven flow to engender such flow morphologies. Interestingly, the size, shape, and frequency of the droplets can be tuned by varying the field intensity, location of the electric field, surface properties of the channel or fluids, viscosity ratio of the fluids, and the flow ratio of the phases. Higher field intensity with lower interfacial tension is found to facilitate the oil droplet formation with a higher throughput inside the hydrophilic microchannels. The method is successful in breaking down the regular pressure‐driven flow patterns even when the fluid inlets are exchanged in the microchannel. The simulations identify the conditions to develop interesting flow morphologies, such as (i) an array of miniaturized spherical or hemispherical or elongated oil drops in continuous water phase, (ii) “oil‐in‐water” microemulsion with varying size and shape of oil droplets. The results reported can be of significance in improving the efficiency of multiphase microreactors where the flow patterns composed of droplets are preferred because of the availability of higher interfacial area for reactions or heat and mass exchange.     

Disposable Amperometric Sensors for Thiols with Special Reference to Glutathione

The antioxidant ‘reduced glutathione’ tripeptide is conventionally called glutathione (GSH). The oxidized form is a sulfur‐sulfur linked compound, known as glutathione disulfide (GSSG). Glutathione is an essential cofactor for antioxidant enzymes; it provides protection also for the mitochondria against endogenous oxygen radicals. The ratio of these two forms can act as a marker for oxidative stress. The majority of the methods available for estimation of both the forms of glutathione are based on colorimetric and electrochemical assays. In this study, electrochemical sensors were developed for the estimation of both GSH and GSSG. Two different types of transducers were used: i) screen‐printed three‐electrode disposable sensor (SPE) containing carbon working electrode, carbon counter electrode and silver/silver chloride reference electrode; ii) three‐electrode disposable system (CDE) consisting of three copper electrodes. 5,5′‐dithiobis(2‐nitrobenzoic acid) (DTNB) was used as detector element for estimation of total reduced thiol content. The enzyme glutathione reductase along with a co‐enzyme reduced nicotinamide adenine dinucleotide phosphate was used to estimate GSSG. By combining the two methods GSH can also be estimated. The detector elements were immobilized on the working electrodes of the sensors by bulk polymerization of acrylamide. The responses were observed amperometrically. The detection limit for thiol (GSH) was less than 0.6 ppm when DTNB was used, whereas for GSSG it was less than 0.1 ppm.     

Azadirachta indica leaves mediated green synthesized copper oxide nanoparticles induce apoptosis through activation of TNF-α and caspases signaling pathway against cancer cells

Green nanotechnology elucidates highly prioritized anticancer activity. We synthesized Copper oxide nanoparticles (CuONPs) using leaves of Azadirachta indica (A. indica) plants and studied the molecular mechanism of cancer cell apoptosis. After their synthesis, with the help of expository tools like Fourier transform infrared spectroscopy (FT-IR), Transmission electron microscopy (TEM), Dynamic light scattering (DLS) and surface zeta potential we confirmed the successful synthesis of CuONPs. Here, crystalline structure of green synthesized CuONPs of 36?±?8?nm size and spherical shape was able to kill MCF-7 and Hela cells, estimated by MTT assay. Successful internalization of Cu⁺² ions inside the cell was estimated by the atomic absorption study. Cellular uptake of Cu⁺² ions inflicted significant Reactive Oxygen Species (ROS) generation inside the cancer cells, thereby leading to DNA fragmentation as observed by DAPI staining. In in vivo model, CuONPs reduced the breast tumor volume in Balb/C mice and increased the mean survival time through the alteration of pro-inflammatory cytokines level. In case of both in vivo and in vitro models, CuONPs altered the pro-inflammatory cytokine level and pro-apoptotic protein expressions. In future, green synthesized CuONPs might be beneficial for its application as an anticancer drug in in vivo (mice model) and in vitro, though further study is needed on its toxicity.     

Quantum superarrivals and information transfer through a time-varying boundary

The time-dependent Schrödinger equation is solved numerically for the case of a Gaussian wave packet incident on a time-varying potential barrier. The time evolving reflection and transmission probabilities of the wave packet are computed for several different time-dependent boundary conditions obtained by reducing or increasing the height of the potential barrier. We show that in the case when the barrier height is reduced to zero, a time interval is found during which the reflection probability is larger (superarrivals) compared to the unperturbed case. We further show that the transmission probability exhibits superarrivals when the barrier is raised from zero to a finite value of its height. Superarrivals could be understood by ascribing the features of a real physical field to the Schrödinger wave function which acts as a carrier through which a disturbance, resulting from the boundary condition being perturbed, prpagates from the barrier to the detectors measuring reflected and transmitted probabilities. The speed of propagation of this effect depends upon the rate of reducing or raising the barrier height, thus suggesting an application for secure information transfer using superarrivals.     

Structural and spectroscopic properties of Ru(II) complexes of 4-(aryl)thiosemicarbazones of thiophen-2-carbaldehyde

Six Ru(II) complexes of formula [Ru(L)₂(PPh₃)₂] have been prepared where LH = 4-(aryl)thiosemicarbazones of thiophen-2-carbaldehyde. X-ray crystal structures of five of the complexes are reported. In all the complexes ruthenium is six coordinate with a distorted octahedral cis-P₂, cis-N₂, trans-S₂ donor environment, and each of the two thiosemicarbazone ligands are coordinated in a bidentate fashion forming a four membered chelate ring. The complexes undergo a one-electron oxidation at ～0.5 V vs. Ag/AgCl. The EPR spectrum of the electrochemically oxidized solution at 100 K shows a rhombic signal, with transitions at g₁ = 2.27, g₂ = 2.00 and g₃ = 1.80. DFT calculations on one of the complexes suggest that there is 35% ruthenium and 17% sulfur orbital contribution to the HOMO. These results suggest that the assignment of metal atom oxidation states in these compounds is not unambiguous.     

Synthesis,crystal structure and fluorescence properties of two dinuclear zinc(II) complexes incorporating tridentate (NNO) Schiff bases

Reactions of hydrated zinc(II) trifluoroacetate and sodium azide with two tridentate Schiff bases HL¹ (2-((E)-(2-(dimethylamino)ethylimino)methyl)-4-chlorophenol) and HL² (2-((E)-(2-(dimethylamino)ethylimino)methyl)-4-bromophenol) under the same reaction conditions yielded two dinuclear isostructural zinc(II) complexes, [Zn(L¹)(N₃)]₂ (1) and [Zn(L²)(N₃)]₂ (2), respectively. The complexes were characterized systematically by elemental analysis, UV–Vis, FT-IR, and ¹H NMR spectroscopic methods. Single-crystal X-ray diffraction studies reveal that each of the dinuclear complexes consists of two crystallographically independent zinc(II) ions connected by double bridging phenoxides. All zinc(II) ions in 1 and 2 are surrounded by similar donor sets and display distorted square–pyramidal coordination geometries. The ligands and complexes reveal intraligand ¹(π → π*) flourescence. The enhancement of the fluorescence intensities for the complexes compared to the ligands indicates their potential to serve as photoactive materials.     

Thermodynamic and spectroscopic studies on the nickel arachidate-RNA polymerase Langmuir-Blodgett monolayer

The Langmuir-Blodgett (LB) monolayers offer a unique system to study molecular interaction at the air-water interface with reduced dimensionality. In order to develop this further to follow macromolecular interactions at equilibrium, we first characterized the Ni (II)-arachidate (NiA) monolayer at varying conditions. Subsequently, the interaction between NiA and histidine-tagged RNA polymerase (HisRNAP) were also studied. LB films of arachidic acid-NiA and NiA-RNAP with different mole fractions were fabricated systematically. Surface pressure versus area per molecule (P-A) isotherms were registered, and the excess Gibbs energy of mixing was calculated. The LB films were then deposited on solid supports for Fourier transform infrared (FTIR) spectroscopic measurements. The FTIR spectra revealed the change in the amount of incorporated Ni (II) ions into the arachidic acid monolayer with the change in pH and the increasing mole fraction of RNAP in the NiA monolayer with its increasing concentration in the subphase. The system developed here seems to be robust and can be utilized to follow macromolecular interactions.     

Synthesis, conformational analysis and biological studies of cyclic cationic antimicrobial peptides containing sugar amino acids

Sugar amino acid based 24-membered macrocyclic C2-symmetric cationic peptides were designed and synthesized. The cationic group was introduced in the sugar amino acids. The conformation of these cyclic compounds was ascertained through NMR techniques, which proved they were amphipathic in nature. All the compounds were bacteriolytic, showed good activity against the Gr(+ve) and Gr(-ve) bacteria, and exhibited low hemolytic activity.