Negative‐pressure‐induced collector for a self‐balance free‐flow electrophoresis device

Uneven flow in free‐flow electrophoresis (FFE) with a gravity‐induced fraction collector caused by air bubbles in outlets and/or imbalance of the surface tension of collecting tubes would result in a poor separation. To solve these issues, this work describes a novel collector for FFE. The collector is composed of a self‐balance unit, multisoft pipe flow controller, fraction collector, and vacuum pump. A negative pressure induced continuous air flow rapidly flowed through the self‐balance unit, taking the background electrolyte and samples into the fraction collector. The developed collector has the following advantages: (i) supplying a stable and harmonious hydrodynamic environment in the separation chamber for FFE separation, (ii) effectively preventing background electrolyte and sample flow‐back at the outlet of the chamber and improving the resolution, (iii) increasing the preparative scale of the separation, and (iv) simplifying the operation. In addition, the cost of the FFE device was reduced without using a multichannel peristaltic pump for sample collection. Finally, comparative FFE experiments on dyes, proteins, and cells were carried out. It is evident that the new developed collector could overcome the problems inherent in the previous gravity‐induced self‐balance collector.     

A Self‐Sampling‐and‐Flow Biosensor for Continuous Monitoring

A self‐sampling‐and‐flow biosensor was fabricated by sandwiching a nitrocellulose strip on the working electrode side of the double‐sided microporous gold electrodes and a wicking pad on the counter electrode side. The double‐sided microporous electrodes were formed by plasma sputtering of gold on a porous nylon substrate. Sample was taken up to the enzyme‐immobilized working electrode by the capillary action of the front nitrocellulose strip dipped into the sample solution, analyzed electrochemically at the enzyme‐immobilized electrode, and diffuses out to the backside wicking pad through the micropores of the electrodes, constituting a complete flow cell device with no mechanical liquid‐transporting device. Biosensor was formed by co‐immobilizing the glucose oxidase and electron transfer mediator (ferrocene acetic acid) on the thioctic acid self‐assembled monolayer‐modified working electrode. A typical response time of the biosensor was about 5 min with the sensitivity of 2.98 nA/mM glucose, providing linear response up to 22.5 mM. To demonstrate the use of self‐sampling‐and‐flow biosensor, the consumption rate of glucose in the presence of yeast was monitored for five days.     

A smartphone‐based on‐site nucleic acid testing platform at point‐of‐care settings

We developed a smartphone‐based on‐site nucleic acid testing (NAT) platform that can image and analyze lateral flow nucleic acid assays at point‐of‐care settings. An inexpensive add‐on was devised to run lateral flow assays while providing homogeneous ambient light for imaging. In addition, an Android app with a user‐friendly interface was developed for the result analysis and management. Linear color calibration is implemented inside the app to minimize the colorimetric reaction difference between smartphones. A relationship function between nucleic acid concentration and colorimetric reaction was established and evaluated by leave‐one‐out cross validation. The predicted concentration and true concentration showed a good agreement with an R‐squared value of 0.96. This smartphone‐based NAT platform can be used to diagnose infectious diseases and monitor disease progression, and assess treatment efficacy, especially for resource‐limited settings.     

Physicochemical characterization of the thermo‐induced self‐assembly of thermo‐responsive PDMAEMA‐b‐PDEGMA copolymers

Diblock copolymers of poly[2‐(dimethylamino)ethyl methacrylate]‐block‐poly[di(ethylene glycol) methyl ether methacrylate], PDMAEMA‐b‐PDEGMA, were synthesized by reversible addition–fragmentation chain transfer polymerization. The block ratio was varied to study the influence on the lower critical solution temperature and the corresponding phase transition in water. Therefore, turbidimetry, differential scanning calorimetry (DSC), dynamic light scattering (DLS), and laser Doppler velocimetry were applied. Additionally, asymmetric flow field‐flow fractionation (AF4) coupled to DLS and multiangle laser light scattering (MALLS) was established as an alternative route to characterize these systems in terms of molar mass of the polymer chain and size of the colloids after the phase transition. It was found that AF4–MALLS allowed accurate determination of molar masses in the studied range. Nevertheless, some limitations were observed, which were critically discussed. The cloud point and phase transition of all materials, as revealed by turbidimetry, could be confirmed by DSC. For block copolymers with block ratios in the range of 50:50, a thermo‐induced self‐assembly into micellar and vesicular structures with hydrodynamic radii (R_h) of around 25 nm was observed upon heating. At higher temperatures, a reordering of the self‐assembled structures could be detected. The thermo‐responsive behavior was further investigated in dependence of pH value and ionic strength. Variation of the pH value mainly influences the solubility of the PDMAEMA segment, where a decrease of the pH value increases the transition temperature. An increase of ionic strength leads to a reduction of the cloud point due to the screening of electrostatic interactions. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015 , 53, 924–935     

Fast reversed‐phase liquid chromatographic separation of proteins by flow‐through poly(styrene‐co‐divinylbenzene) microspheres

With the explosive growth of the bioscience and biopharmaceuticals, the demand for high efficient analysis and separation of proteins is urgent. High‐performance liquid chromatography is an appropriate technology for this purpose, and the stationary phase is the kernel to the separation efficiency. In this study, flow‐through poly(styrene‐co‐divinylbenzene) microspheres characteristic of the binary pores, i.e. flow‐through pores and mesopores, were synthesized; this special porous structure would benefit the convective mass transfer while guarantee the high specific surface area. Owing to the hydrophobic nature, poly(styrene‐co‐divinylbenzene) microspheres were suitable as the reversed‐phase stationary phase for separation of proteins. For the high permeability of the poly(styrene‐co‐divinylbenzene) microspheres packed column, fast separation of the studied six proteins in ～2 min was achieved. The recoveries of studied proteins were acceptable in the range of 79.0–99.4%. The proposed column had good pH stability of 1–13 and repeatability. Moreover, the column was applied for egg white fast separation, further demonstrating its applicability for complex bio‐sample separation. The flow‐through poly(styrene‐co‐divinylbenzene) microspheres were promising for fast separation of large molecules.     

Self‐Regulation in Flow‐Induced Structure Formation of Polypropylene

Flow‐induced structure formation is investigated with in situ wide‐angle X‐ray diffraction with high acquisition rate (30 Hz) using isotactic polypropylene in a piston‐driven slit flow with high wall shear rates (up to ≈900 s⁻¹). We focus on crystallization within the shear layers that form in the high shear rate regions near the walls. Remarkably, the kinetics of the crystallization process show no dependence on either flow rate or flow time; the crystallization progresses identically regardless. Stronger or longer flows only increase the thickness of the layers. A conceptual model is proposed to explain the phenomenon. Above a certain threshold, the number of shish‐kebabs formed affects the rheology such that further structure formation is halted. The critical amount is reached already within 0.1 s under the current flow conditions. The change in rheology is hypothesized to be a consequence of the “hairy” nature of shish. Our results have large implications for process modelling, since they suggest that for injection molding type flows, crystallization kinetics can be considered independent of deformation history.

     

Cell‐based studies of the first‐in‐class half‐sandwich Ir(III) complex containing histone deacetylase inhibitor 4‐phenylbutyrate

We report on a cytotoxic half‐sandwich iridium(III) complex [Ir(η⁵‐Cp^ph)(phen)(PB)]PF₆ ( 1‐PB ), containing a monodentate coordinated O‐donor 4‐phenylbutyrato ligand (PB) belonging to the family of histone deacetylase inhibitors (HDACi); HCp^ph = (2,3,4,5‐tetramethylcyclopenta‐2,4‐dien‐1‐yl)benzene, phen = 1,?10‐phenanthroline. The solution behaviour studies indicated that complex 1‐PB partially hydrolysed in the mixture of methanol and water (1:4, v/v), resulting in the release of the PB ligand. The extent of the PB ligand release increased in the presence of 2 molar equiv. of the reduced glutathione (GSH). Complex 1‐PB exhibited comparable in vitro cytotoxicity against the cisplatin‐sensitive (IC₅₀ = 15.8 μM) and ‐resistant (IC₅₀ = 13.0 μM) variants of the A2780 human ovarian carcinoma cells, while its potency against the MRC‐5 human normal fibroblast cells was markedly lower (IC₅₀ = 124.1 μM). The cytotoxicity studies revealed an ability of complex 1‐PB to overcome the acquired resistance against cisplatin, with the resistance factor (RF = 0.8) being markedly lower than for complex 1‐Cl (RF = 1.8) and cisplatin (RF = 2.9). The A2780 cell‐based flow cytometry experiments showed different cell cycle modification induced by complex 1‐PB and cisplatin, induction of production of reactive oxygen species, and higher mitochondria membrane potential depleted cell populations after the treatment by complex 1‐PB as compared with cisplatin. In the cell‐free assay, complex 1‐PB inhibited the HDAC activity to ca 66% as compared to ca 74% valid for NaPB. The [Ir(η⁵‐Cp^ph)(phen)(H₂O)]²⁺ species ( 1‐OH ₂ ), representing the hydrolysis product of both complexes 1‐PB and 1‐Cl , induced hydroxyl radical from the hydrogen peroxide, as proved by the EPR spin trapping studies with the 5‐(diethoxyphosphoryl)‐5‐methyl‐1‐pyrroline‐N‐oxide (DEPMPO) spin trap.     

Chip‐Based Free‐Flow Electrophoresis with Integrated Nanospray Mass‐Spectrometry

Free‐flow electrophoresis is an ideal tool for preparative separations in continuous microflow. With the approach presented herein for coupling free‐flow electrophoresis and mass spectrometry it is now also possible to trace non‐fluorescent compounds and identify them by means of mass spectrometry. The functionality of the method and its potential as an integrated separation unit for microflow synthesis is demonstrated by application to a multicomponent [3+2]‐cycloannulation.     

A New Solution—phase Parallel Synthesis of 2—Alkyamino—3—aryl—5—phenylmethylene—3,5—dihydro—4H—imidazol—4—ones

Thirteen new 2-alkylaminoimidazolones(4) wre rapidly synthesized by a new solution-phase parallel synthetic method,which includes aza-Wittig reaction of iminophosphorane(1) with aromatic isocyanate to give carbodi-imide(2) and subsequent reaction of 2 with various aliphatic primary amine in a parallel fashion.The products were confirmed by ^1H NMR,MS,IR and X-ray crystallographic analysis.The unusual selectivity of the cyclization was probably due to the deometry of the guanidine intermediate.     

Preparation and characterization of quaternized poly (2,2,2‐trifluoroethyl methacrylate‐co‐N‐vinylimidazole) membrane for vanadium redox flow battery

Aiming to develop a suitable ion exchange membrane for vanadium redox flow battery (VRB), a new kind of imidazolium salt type anion exchange membrane based on the copolymer of N‐vinylimidazole and 2,2,2‐trifluoroethyl methacrylate has been prepared. The membrane is characterized by means of water uptake, ion‐exchange capacity, ionic conductivity, and thermal stability. Furthermore, a VRB with this membrane is assembled, and the performance of such VRB is evaluated. The permeability experiments show that this membrane has reasonable low permeability of vanadium ions. The coulombic efficiency (CE) and energy efficiency (EE) of VRB with the synthesized membrane are 99.5% and 75.0%, whereas the CE and EE of the VRB with Nafion® 117 membrane are 82.6% and 72.6%, respectively. The synthesized membrane shows good chemical stability in VRB via more than 4000 cycles test. Therefore, this membrane shows good applicable potential in VRB. Copyright © 2012 John Wiley & Sons, Ltd.     

Carrier ampholyte‐free free‐flow isoelectric focusing for separation of protein

Free‐flow isoelectric focusing (FFIEF) has the merits of mild separation conditions, high recovery and resolution, but suffers from the issues of ampholytes interference and high cost due to expensive carrier ampholytes. In this paper, a home‐made carrier ampholyte‐free FFIEF system was constructed via orientated migration of H⁺ and OH^? provided by electrode solutions. When applying an electric field, a linear pH gradient from pH 4 to 9 (R² = 0.994) was automatically formed by the electromigration of protons and hydroxyl ions in the separation chamber. The carrier ampholyte‐free FFIEF system not only avoids interference of ampholyte to detection but also guarantees high separation resolution by establishing stable pH gradient. The separation selectivity was conveniently adjusted by controlling operating voltage and optimizing the composition, concentration and flow rate of the carrier buffer. The constructed system was applied to separation of proteins in egg white, followed by MADLI‐TOF‐MS identification. Three major proteins, ovomucoid, ovalbumin and ovotransferrin, were successfully separated according to their pI values with 15 mmol/L Tris‐acetic acid (pH = 6.5) as carrier buffer at a flow rate of 12.9 mL/min.     

Enhancing resolution of free‐flow zone electrophoresis via a simple sheath‐flow sample injection

In this work, a simple and novel sheath‐flow sample injection method (SFSIM) is introduced to reduce the band broadening of free‐flow zone electrophoresis separation in newly developed self‐balance free‐flow electrophoresis instrument. A needle injector was placed in the center of the separation inlet, into which the BGE and sample solution were pumped simultaneously. BGE formed sheath flow outside the sample stream, resulting in less band broadening related to hydrodynamics and electrodynamics. Hemoglobin and C‐phycocyanin were successfully separated by the proposed method in contrast to the poor separation of free‐flow electrophoresis with the traditional injection method without sheath flow. About 3.75 times resolution enhancement could be achieved by sheath‐flow sample injection method.     

A Continuous Flow Process Using a Sequence of Microreactors with In‐line IR Analysis for the Preparation of N,N‐Diethyl‐4‐(3‐fluorophenylpiperidin‐4‐ylidenemethyl)benzamide as a Potent and Highly Selective δ‐Opioid Receptor Agonist

This article describes the design, optimisation and development of a continuous flow synthesis of N,N‐diethyl‐4‐(3‐fluorophenylpiperidin‐4‐ylidenemethyl)benzamide, a potent δ‐opioid receptor agonist developed by AstraZeneca. The process employs a sequence of flow‐based microreactors, with integrated purification employing solid‐supported reagents and in‐line IR analytical protocols using a newly developed ReactIR flow cell. With this monitoring device, initiation of the fourth input flow stream can be precisely controlled during the synthesis.     

Flow‐Guided Assembly Processes

This Concept article focuses on capillary, hydrodynamics and electrokinetic flow‐guided assembly processes that can produce patterned or gradient functional surfaces either on solid surfaces or in deep micro‐ and nanoscale channels. This concept has the potential to produce low‐cost nanostructures, internal surface modifications, and devices in nanomedicine.     

Isocyanide‐Based Three‐Component Synthesis of Highly Substituted 1,6‐Dihydro‐6,6‐dimethylpyrazine‐2,3‐dicarbonitrile, 3,4‐Dihydrobenzo[g]quinoxalin‐2‐amine,and 3,4‐Dihydro‐3,3‐dimethyl‐quinoxalin‐2‐amine Derivatives

A novel and efficient isocyanide‐based multicomponent reaction between alkyl or aryl isocyanides 1 , 2,3‐diaminomaleonitrile ( 2 ), naphthalene‐2,3‐diamines ( 6 ) or benzene‐1,2‐diamine ( 9 ), and 3‐oxopentanedioic acid ( 3 ) or Meldrum's acid ( 4 ) or ketones 7 was developed for the ecologic synthesis, at room temperature under mild conditions, of 1,6‐dihydropyrazine‐2,3‐dicarbonitriles 5a – 5f in H₂O without using any catalyst, and of 3,4‐dihydrobenzo[g]quinoxalin‐2‐amine and 3,4‐dihydro‐3,3‐dimethyl‐quinoxalin‐2‐amine derivatives 8a – 8g and 10a – 10e , respectively, in the presence of a catalytic amount of p‐toluenesulfonic acid (TsOH) in EtOH, in good to excellent yields (Scheme 1).     

A Simple One‐Pot Synthesis of N‐Alkyl‐2,5‐diaryl‐1,3‐dioxol‐4‐amines

An efficient procedure for the synthesis of N‐alkyl‐2,5‐diaryl‐1,3‐dioxol‐4‐amines 3 via a one‐pot reaction of aromatic aldehydes 2 and alkyl isocyanides 1 at room temperature in good yields is described (Scheme 1, Table).     

Alternative Synthesis of 2‐Hydroxy‐3,5,5‐trimethylcyclopent‐2‐en‐1‐one

The 2‐hydroxy‐3,5,5‐trimethylcyclopent‐2‐en‐1‐one ( 1 ) was synthesized in 42% yield by rearrangement of epoxy ketone 10 on treatment with BF₃⋅Et₂O under anhydrous conditions. Intermediate 10 was available from the known enone 8 , either via direct epoxidation (60% H₂O₂, NaOH, MeOH; yield 50%), or via reduction to the corresponding allylic alcohol 14 (LiAlH₄, THF), followed by epoxidation ([VO(acac)₂], ^tBuOOH) and reoxidation under Swern conditions, in 37% total yield.