Flexible microfluidic cloth-based analytical devices using a low-cost wax patterning technique

This paper describes the fabrication of microfluidic cloth-based analytical devices (μCADs) using a simple wax patterning method on cotton cloth for performing colorimetric bioassays. Commercial cotton cloth fabric is proposed as a new inexpensive, lightweight, and flexible platform for fabricating two- (2D) and three-dimensional (3D) microfluidic systems. We demonstrated that the wicking property of the cotton microfluidic channel can be improved by scouring in soda ash (Na(2)CO(3)) solution which will remove the natural surface wax and expose the underlying texture of the cellulose fiber. After this treatment, we fabricated narrow hydrophilic channels with hydrophobic barriers made from patterned wax to define the 2D microfluidic devices. The designed pattern is carved on wax-impregnated paper, and subsequently transferred to attached cotton cloth by heat treatment. To further obtain 3D microfluidic devices having multiple layers of pattern, a single layer of wax patterned cloth can be folded along a predefined folding line and subsequently pressed using mechanical force. All the fabrication steps are simple and low cost since no special equipment is required. Diagnostic application of cloth-based devices is shown by the development of simple devices that wick and distribute microvolumes of simulated body fluids along the hydrophilic channels into reaction zones to react with analytical reagents. Colorimetric detection of bovine serum albumin (BSA) in artificial urine is carried out by direct visual observation of bromophenol blue (BPB) colour change in the reaction zones. Finally, we show the flexibility of the novel microfluidic platform by conducting a similar reaction in a bent pinned μCAD.     

Evaluation the pozzolanic reactivity of sonochemically fabricated nano natural pozzolan

Natural pozzolans are appropriate supplementary cementitious materials in cement and concrete industry. A simple sonochemical method was developed to synthesize nanostructures of natural pozzolan. Chemical composition, crystallinity, morphology and reactivity of the natural pozzolan samples were compared before and after the sonochemical process, by using powder X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Thermal Gravimetry and Differential Thermal Analysis (TG/DTA). Compressive strength tests were performed to evaluate the properties of blended cements incorporating nano natural pozzolan. Under optimized conditions, the nano natural pozzolans showed a superior reactivity as compared with the bulk natural pozzolan. Also higher compressive strength was obtained for the cement specimen incorporating nano natural pozzolan.     

The reduction of rotational ambiguity in soft-modeling by introducing hard models

Rotational ambiguity is a major problem in the application of soft-modeling analysis to a variety of multivariate mixture resolution problems and particularly important in the analysis of kinetic data. Soft-modeling analyses rely on constraints that restrict the concentration profiles and/or the spectral responses of all components. The main goal of this work is to demonstrate how a hard-modeling constraint on concentration profiles drastically decreases the extent of the rotational ambiguity. Therefore, in the present paper the discussion is focused on systems in which hard-modeling information is available. The results of simulated examples reveal that the utilized hard constraint decreases the rotational ambiguity in estimated concentration profile even components that do not take part in the explicit model. In addition, the rate constant of known reaction is determined in this method.     

Aptamer-based sensor for diclofenac quantification using carbon nanotubes and graphene oxide decorated with magnetic nanomaterials

In this contribution, a novel label-free electrochemical biosensor for diclofenac (DCF) detection was developed using the unique properties of acid-oxidized carbon nanotubes (CNT), graphene oxide (GO), and Fe₃O₄ magnetic nanomaterials. The GO sheets and CNT were interlinked by ultrafine Fe₃O₄ nanoparticles forming three-dimensional (3D) architectures. The characterization of the nanocomposite was studied by scanning electron microscopy (SEM), energy-dispersive X-ray (EDS), and wavelength-dispersive X-ray (WDX) spectroscopy. Initially, aminated detection probe (aptamer) was surface-confined on the CNT/GO/Fe₃O₄ nanocomposite via the covalent amide bonds formed by the carboxyl groups on the CNT/GO and the amino groups on the oligonucleotides at the 5′ end. Our constructed folding-based electrochemical sensor was used for detection of target molecule utilizing structure-switching aptamers. Signaling arose from changes in electron transfer efficiency upon target-induced changes in the conformation of the aptamer probe. These changes were readily monitored using differential pulse voltammetry technique. This sensor exhibited binding affinities ranging from 100 to 1300 pM with a low detection limit of 33 pM.     

Crystal growth of thin [Zn<Subscript>2</Subscript>(H<Subscript>2</Subscript>N-BDC)<Subscript>2</Subscript>(4-bpdb)] · 3DMF metal–organic framework nanostructure on functionalized surfaces: study of structure effect on methyldopa adsorption affinity

Thin films of a three-dimensional porous Zn(II)-based metal–organic framework, [Zn₂(NH₂-BDC)₂(4-bpdb)] · 3DMF (TMU-17-NH₂), containing azine-functionalized pores, were deposited on surfaces of silk fiber via a stepwise manner. The effect of sequential dipping steps in growth of TMU-17-NH₂ has been studied. These systems depicted a decrease in the size accompanying a decrease in the sequential dipping steps. The TMU-17-NH₂ has been used as matrices for the adsorption and in vitro guest delivery of methyldopa (MD).     

Palladium‐catalyzed cyanation reaction of aryl halides using K4[Fe(CN)6] as non‐toxic source of cyanide under microwave irradiation

An efficient method for preparation of aryl nitriles—using [Pd{C₆H₂(CH₂CH₂ NH₂)‐(OMe)₂,3,4} (µ‐Br)]₂ complex as an efficient catalyst and K₄[Fe(CN)₆] as a green cyanide source—from aryl bromides, aryl iodides and aryl chlorides under microwave irradiation has been reported. This complex has been demonstrated to be an active and efficient catalyst for this reaction. Using a catalytic amount of this synthesized palladium complex in DMF at 130 °C led to production of the cyanoarenes in excellent yields in short reaction times. Copyright © 2010 John Wiley & Sons, Ltd.     

Synthesis of Polyfunctionalized 1,4‐Dihydropyridine‐Fused‐1,3‐Diazaheterocycles: One‐Pot Reaction of 1,1‐Bis(methylthio)‐2‐nitroethylene, 1,n‐Diamine,Arylaldehyde, and Malononitrile

An efficient, one‐pot synthetic protocol for polyfunctionalized 1,4‐dihydropyridine‐fused‐1,3‐diazaheterocycles, a class of biologically active compounds, starting from 1,1‐bis(methylthio)‐2‐nitroethylene, 1,n‐diamine, arylaldehyde, and malononitrile is described. The reactions are completed within 12–15 h under refluxing conditions and in the presence of 10 mol % of piperidine as a basic catalyst to produce the title compounds in 60–75% yields.     

Theoretical Study of Stability and Electronic Characteristics in Various Complexes of Psoralen as an Anticancer Drug in Gas Phase,Water and CCl4 Solutions

The present research employs density functional theory(DFT) computations to analyze the structure and energy of complexes formed by psoralen drug with alkali(Li⁺, Na⁺, K⁺) and alkaline earth(Be²⁺, Mg²⁺, Ca²⁺) metal cations. The computations are conducted on M06-2X/aug-cc-pVTZ level of theory in the gas phase and solution. The Atoms in Molecules(AIM) and natural bond orbital(NBO) analyses are applied to evaluating the characterization of bonds and the atomic charge distribution, respectively. The results show that the absolute values of binding energies decrease with going from the gas phase to the solution. Furthermore, the considered complexes in the water(as a polar solvent) are more stable than the CCl₄(as a non-polar solvent). The DFT based chemical reactivity indices, such as molecular orbital energies, chemical potential, hardness and softness are also investigated. The outcomes show that the considered complexes have high chemical stability and low reactivity from the gas phase to the solution. Finally, charge density distributions and chemical reactive sites of a typical complex explored in this study are obtained by molecular electrostatic potential surface.     

Dual mechanisms of HNO generation by a nitroxyl prodrug of the diazeniumdiolate (NONOate) class

Here we describe a novel caged form of the highly reactive bioeffector molecule, nitroxyl (HNO). Reacting the labile nitric oxide (NO)- and HNO-generating salt of structure iPrHN-N(O)═NO(-)Na(+) (1, IPA/NO) with BrCH(2)OAc produced a stable derivative of structure iPrHN-N(O)═NO-CH(2)OAc (2, AcOM-IPA/NO), which hydrolyzed an order of magnitude more slowly than 1 at pH 7.4 and 37 °C. Hydrolysis of 2 to generate HNO proceeded by at least two mechanisms. In the presence of esterase, straightforward dissociation to acetate, formaldehyde, and 1 was the dominant path. In the absence of enzyme, free 1 was not observed as an intermediate and the ratio of NO to HNO among the products approached zero. To account for this surprising result, we propose a mechanism in which base-induced removal of the N-H proton of 2 leads to acetyl group migration from oxygen to the neighboring nitrogen, followed by cleavage of the resulting rearrangement product to isopropanediazoate ion and the known HNO precursor, CH(3)-C(O)-NO. The trappable yield of HNO from 2 was significantly enhanced over 1 at physiological pH, in part because the slower rate of hydrolysis for 2 generated a correspondingly lower steady-state concentration of HNO, thus, minimizing self-consumption and enhancing trapping by biological targets such as metmyoglobin and glutathione. Consistent with the chemical trapping efficiency data, micromolar concentrations of prodrug 2 displayed significantly more potent sarcomere shortening effects relative to 1 on ventricular myocytes isolated from wild-type mouse hearts, suggesting that 2 may be a promising lead compound for the development of heart failure therapies.     

Characterization of amorphous organic thin films, determination of precise model for spectroscopic ellipsometry measurements

The optical properties of tris(8-hydroxyquinoline) aluminum (Alq₃), N,N′-diphenyl-N,N′-bis(1-naphthyl)-1-1′biphenyl-4,4″diamine (α-NPD) and other amorphous organic materials for OLEDs application, e.g. 4,4-bis(2,2-diphenyl vinyl)-1,1-biphenyl (DPVBI) and Spiro-DPVBI have been studied by multi-angle spectroscopic ellipsometry (SE). The thin films of these materials have been deposited by organic vapor phase deposition (OVPD). The structural characterization has been performed using atomic force microscopy (AFM) and X-ray reflectometry (XRR). Comparison of the measurements using these different independent techniques enables the precise determination of the optical model for dielectric function of these thin films. The detail analyses on Alq₃ and α-NPD show that the Kim model with Gaussian broadening provides a significantly better fit to the ellipsometry data than the frequently used harmonic oscillator model. This conclusion is further proved by performing similar measurements on other amorphous organic samples for OLEDs application, e.g. DPVBI and Spiro-DPVBI. This result can be explained by the characteristic features of electronic states in organic molecules.