Search

We developed a novel strategy for modification of paper cellulose with water-insoluble oxidants for distance readout of reducing substances on microfluidic paper-based analytical devices (μPADs). Water-insoluble oxidants were formed and modified onto paper cellulose through the redox reaction that occurred between paper cellulose and potassium permanganate deposited on the paper channel, developing a yellowish-brown color on the channel. As aqueous solutions containing reducing substances flowed along the channel, reducing substances were consumed owing to the redox reaction that occurred between oxidants and reducing substances until the reducing substances were depleted, forming a discolored zone on the yellowish-brown channel. The redox reaction between insoluble oxidants and reducing substances on the paper cellulose could be used for distance-based detection of a wide variety of reducing substances, which is similar to the classical potassium permanganate titration that employs the redox reaction that occurred between potassium permanganate and reducing substances. We believe that this method will broaden the analytical applications of distance-based detection on μPADs. This method was applied to ascorbic acid assay and captopril assay in real samples with analytical results comparing well with the labeled values, demonstrating its great potential in real sample analysis.

Retinitis pigmentosa (RP) is an inherited retinal dystrophy causing progressive and irreversible loss of retinal photoreceptors. Here, we developed a genome-editing tool characterized by the versatility of prime editors (PEs) and unconstrained PAM requirement of a SpCas9 variant (SpRY), referred to as PESpRY. The diseased retinas of Pde6b-associated RP mouse model were transduced via a dual AAV system packaging PESpRY for the in vivo genome editing through a non-NGG PAM (GTG). The progressing cell loss was reversed once the mutation was corrected, leading to substantial rescue of photoreceptors and production of functional PDE6β. The treated mice exhibited significant responses in electroretinogram and displayed good performance in both passive and active avoidance tests. Moreover, they presented an apparent improvement in visual stimuli-driven optomotor responses and efficiently completed visually guided water-maze tasks. Together, our study provides convincing evidence for the prevention of vision loss caused by RP-associated gene mutations via unconstrained in vivo prime editing in the degenerating retinas.

We developed a comprehensive training module for the undergraduates majoring in chemical education with a simple microfluidic experiment. The students were required to read a scientific reference o...

We described a simple method for detection of Fe on a thread-based analytical device. Fe reacts with 1,10-phenanthroline to form a colored band on a cotton thread; the length was measured to quantify the contents of Fe using a ruler. This method has the advantages of easy operation, low cost, easy fabrication, and reduced sample/reagent consumption. Furthermore, this method is free of any electronic equipment such as camera and digital scanner. These features make this method suitable as a laboratory experiment in universities and colleges. This laboratory experiment is designed as one of selected experiments of the Comprehensive Chemistry Experiment course for the students majoring in chemistry, for the sixth and seventh semester. The students enjoyed fabricating the thread-based analytical device and used it to detect the contents in unknown samples. This laboratory experiment could be completed within 3 h.

With the popularization of Web 2.0 technology and people’s higher and higher requirements for user experience, traditional Web interfaces can no longer meet people’s requirements for interactive features. Web front-end development technologies are getting more and more attention, and major industries are developing Web front-ends. The demand for talents has also increased substantially. This article proposes a new teaching model for the web front-end development technology course in the teaching process, and discusses the specific teaching reform and implementation methods in the new model.

We described a method for electrophoretic separation of food dyes on a thread-based microfluidic analytical device. A cross channel thread-based microfluidic analytical device was fabricated and used to separate a mixture of food dyes. By controlling and adjusting the potentials applied onto four reservoirs, carmine and sunset yellow could be separated within 2 min. This method has the advantages of low cost, fast separation, and easy fabrication and operation, which make this very suitable for performing as a demonstration in universities. The students enjoyed this demonstration and presented some interesting and constructive questions after the demonstration, which indicated that the students were interested in the demonstration. This demonstration could also be modified to be a laboratory experiment which could be carried out within 3 h.

We described a strategy to perform multistep operations on a simple laminated paper-based separation device by using electrokinetic flow to manipulate the fluids. A laminated crossed-channel paper-based separation device was fabricated by cutting a filter paper sheet followed by lamination. Multiple function units including sample loading, sample injection, and electrophoretic separation were integrated on a single paper based analytical device for the first time, by applying potential at different reservoirs for sample, sample waste, buffer, and buffer waste. As a proof-of-concept demonstration, mixed sample solution containing carmine and sunset yellow were loaded in the sampling channel, and then injected into separation channel followed by electrophoretic separation, by adjusting the potentials applied at the four terminals of sampling and separation channel. The effects of buffer pH, buffer concentration, channel width, and separation time on resolution of electrophoretic separation were studied. This strategy may be used to perform multistep operations such as reagent dilution, sample injection, mixing, reaction, and separation on a single microfluidic paper based analytical device, which is very attractive for building micro total analysis systems on microfluidic paper based analytical devices.

We described a low-cost method for rapid prototyping of a microfluidic paper-based analytical device by inkjet printing of permanent marker ink. After the evaporation of ink solvent is printed onto the paper, hydrophobic resin remains and forms hydrophobic barriers for microfluidic flow and analysis.

A demonstration is described of electrophoretic separation of carmine and sunset yellow with a paper-based device. The channel in the paper device was fabricated by hand with a wax pen. Electrophoretic separation of carmine and sunset yellow was achieved within a few minutes by applying potential on the channel using a simple and inexpensive power supply. This demonstration could not only motivate the students’ passion in learning analytical chemistry but also introduce two important analytical techniques (microfluidic paper-based analytical devices and electrophoresis) to the classroom. With further modification and improvement, this demonstration may be suitable for students to perform as a laboratory experiment in the teaching lab.

We developed a novel, low-cost and simple method for the fabrication of microfluidic paper-based analytical devices (μPADs) by silanization of filter cellulose using a paper mask having a specific pattern. The paper mask was penetrated with trimethoxyoctadecylsilane (TMOS) by immersing into TMOS-heptane solution. By heating the filter paper sandwiched between the paper mask and glass slides, TMOS was immobilized onto the filter cellulose via the reaction between cellulose OH and TMOS, while the hydrophilic area was not silanized because it was not in contact with the paper mask penetrated with TMOS. The effects of some factors including TMOS concentration, heating temperature and time on the fabrication of μPADs were studied. This method is free of any expensive equipment and metal masks, and could be performed by untrained personnel. These features are very attractive for the fabrication and applications of μPADs in developing countries or resource-limited settings. A flower-shaped μPAD was fabricated and used to determine glucose in human serum samples. The contents determined by this method agreed well with those determined by a standard method.

In a wireless communication system for the high speed railway, system design engineers must have a thorough understanding of the radio-propagation characteristics, which is the essential aspect of wireless network designing and optimization. The channel impulse response can be generated by using slippage correlation measurement. Generally, the influence of the additive white Gaussian noise and the imperfect autocorrelation function is neglected, which will reduce the accuracy of the channel impulse response and the validity of the channel model. This paper proposes on a method which can eliminate the influence of the additive white Gaussian noise and the imperfect autocorrelation function through discrete wavelet transform. This method can provide a reliable guarantee to extract more accurate channel parameters, such as power delay profile, excess delay, and amplitude gain. And the results of simulation turn out that the de-noising method is effective.

We described a facile method for distance-based detection of aluminum on a thread based on the adsorption of formed complex onto thread. Chrome azurol S (CAS) containing Cetyltrimethylammonium Bromide (CTMAB) were used as chromogenic reagent, which reacts with aluminum to form AL-CAS-CTMAB complex on a thread. The complex was adsorbed onto thread to generate a colored band. Aluminum contents could be quantified by measuring the length of colored band on the thread using a ruler, thereby eliminating the need for electronic readout devices and trained personnel. This instrument-free method has features of low cost, easy to operation, fast analysis speed, disposability and low reagents/sample consumption. Moreover, considering that the thread fiber has adsorption capability to various molecules such as metal-ligand complexes and biomolecules, we believe that this technique holds the potentials to be widely adaptable to distance-based chemical and biochemical analysis.

We used a surfactant to fabricate a microfluidic paper-based analytical device (µPAD) by selective modification of hydrophobic filter paper. Hydrophobic tails of the surfactant penetrate and remain...

A simple, rapid, sensitive and high throughput method is described, based on solid-phase disk extraction (SPDE) and gas chromatography-electron capture detection, for the determination of chlorobenzens (CBs) in water samples. The proposed SPDE sample pretreatment method was initially optimized and the optimum experimental conditions were found to be as follows: 500 mL water sample (pH 2.5) extracted and enriched by an Empore 3-stn C18 (octadecyl) SPE disk at flow rate of 5 to 50 mL/min, eluted by 5 mL of acetone and 3 × 5 mL of methylene dichloride. The linearity of the method ranged from 0.02 to 0.4 µg/L for dichlorobenzene isomers, 0.0022-0.044 µg/L for trichlorobenzene isomers, 0.005-0.01 µg/L for tetrachlorobenzene isomers and 0.00025 to 0.005 µg/L for pentachlorobenzenes and hexachlorobenzenes, with correlation coefficients ranging between 0.9991 and 0.9999. The limits of detection were in the low ng/L level, ranging between 0.05 and 4 ng/L. The recoveries of spiked CBs with the external calibration method at different concentration levels in deionized/distilled water, tap water and sea water samples were 99-115, 91-106% and 96-110%, respectively, and with relative standard deviations of 4.5-7.6, 4.2-6.8 and 3.6-6.6% (n = 5), respectively. It is concluded that this method can successfully be applied for the determination of CBs in deionized/distilled water, tap water and sea water samples.

In multiuser multiple-input single-output (MISO) systems, non-linear precoder is able to achieve the theoretical sum capacity of downlink channel with perfect channel state information (CSI). However, the perfect CSI is not available at the transmitter in practical system, especially in frequency division duplex (FDD) system where the imperfect CSI is the delayed, quantized channel direction information relayed back from the receiver through a dedicated feedback channel. So the performance of conventional non-linear precoder degrades significantly. In this paper, a robust non-linear Tomlinson---Harashima precoding (THP) based on sum mean squared error (SMSE) minimization for the downlink of multiuser MISO FDD systems is proposed. The proposed precoder is robust to the channel uncertainties arising from channel delay and quantization error. Furthermore, an improved non-linear THP with channel magnitude information (CMI) consideration is introduced to compensate the instantaneous CMI shortage at the transmitter. Additionally, the computational complexity of both proposed precoders can be reduced remarkably by Cholesky factorization with symmetric permutation. Simulation results demonstrate the improvement in bit error ratio performance and illustrate the SMSE performance of the proposed algorithms compared with conventional THP with perfect CSI in the literature.

A novel three-dimensional hydrodynamic focusing microfluidic device integrated with high-throughput cell sampling and detection of intracellular contents is presented. It has a pivotal role in maintaining the reducing environment in cells. Intracellular reducing species such as vitamin C and glutathione in normal and tumor cells were labeled by a newly synthesized 2,2,6,6-tetramethyl-piperidine-1-oxyl-based fluorescent probe. Hepatocytes are adherent cells, which are prone to attaching to the channel surface. To avoid the attachment of cells on the channel surface, a single channel microchip with three sheath-flow channels located on both sides of and below the sampling channel was developed. Hydrostatic pressure generated by emptying the sample waste reservoir was used as driving force of fluid on the microchip. Owing to the difference between the liquid levels of the reservoirs, the labeled cells were three-dimensional hydrodynamically focused and transported from the sample reservoir to the sample waste reservoir. Hydrostatic pressure takes advantage of its ease of generation on a microfluidic chip without any external pressure pump, which drives three sheath-flow streams to constrain a sample flow stream into a narrow stream to avoid blockage of the sampling channel by adhered cells. The intracellular reducing levels of HepG2 cells and L02 cells were detected by home-built laser-induced fluorescence detector. The analysis throughput achieved in this microfluidic system was about 59–68 cells/min. Copyright © 2013 John Wiley & Sons, Ltd.

The deformation and recovery behaviors of multilayer microcapsules were investigated after being forced to flow through a microchannel. The microchannel device with a constriction (5.7 μm in depth) in the middle was designed, and the multilayer microcapsules with different size and layer thickness (and thereby different mechanical strength) were used. Deformation in the microchannel was observed for all the capsules with a size larger than the constriction height, and its extent was mainly governed by the difference between capsule size and constriction height. The squeezed microcapsules could recover their original spherical shape when the deformation extent was smaller than 16%, whereas permanent physical deformation took place when the deformation extent was larger than 34%. The capsules filled with polyelectrolytes could greatly enhance their shape recovery ability due to the higher osmotic pressure in the capsule interior and could well maintain the preloaded low-molecular-weight dyes regardless of the squeezing.

A new, simple, sensitive and selective method for the simultaneous determination of trace iron and aluminum by catalytic spectrophotometry was presented, based on the catalytic effects of iron and aluminum on the discoloring reaction of xylene cyanol FF proceeded by hydrogen peroxide and potassium periodate in weak nitric acid medium. No catalytic effect was obtained in the presence of hydrogen peroxide or potassium periodate only. With the conditional rate constants determined in reaction systems catalyzed by Al or Fe only, the concentrations of Fe and Al in the samples can be calculated. The method was applied to the simultaneous determination of trace Fe and Al in tap water, lake water, river water and tea leaves without separation and preconcentration.

We described a strategy to perform multistep operations on a simple laminated paper-based separation device by using electrokinetic flow to manipulate the fluids. A laminated crossed-channel paper-based separation device was fabricated by cutting a filter paper sheet followed by lamination. Multiple function units including sample loading, sample injection, and electrophoretic separation were integrated on a single paper based analytical device for the first time, by applying potential at different reservoirs for sample, sample waste, buffer, and buffer waste. As a proof-of-concept demonstration, mixed sample solution containing carmine and sunset yellow were loaded in the sampling channel, and then injected into separation channel followed by electrophoretic separation, by adjusting the potentials applied at the four terminals of sampling and separation channel. The effects of buffer pH, buffer concentration, channel width, and separation time on resolution of electrophoretic separation were studied. This strategy may be used to perform multistep operations such as reagent dilution, sample injection, mixing, reaction, and separation on a single microfluidic paper based analytical device, which is very attractive for building micro total analysis systems on microfluidic paper based analytical devices.

We describe a simple and cost-effective strategy for rapid fabrication of microfluidic paper-based analytical devices and valves by inkjet printing. NaOH aqueous solution was printed onto a hydrophobic filter paper, which was previously obtained by soaking in a trimethoxyoctadecylsilane-heptane solution, allowing selective wet etching of hydrophobic cellulose to create hydrophilic-hydrophobic contrast with a relatively good resolution. Hexadecyltrimethylammonium bromide (CTMAB)-ethanol solution was printed onto hydrophobic paper to fabricate temperature-controlled valves. At low temperature, CTMAB deposited on the paper is insoluble in aqueous fluid, thus the paper remains hydrophobic. At high temperature, CTMAB becomes soluble so the CTMAB-deposited channel becomes hydrophilic, allowing the wicking of aqueous solution through the valve. We believe that this strategy will be very attractive for the development of simple micro analytical devices for point-of-care applications, including diagnostic testing, food safety control, and environmental monitoring.

A method was developed for the fabrication of microfluidic paper-based analytical devices (μPAD). This method was based on the silanisation of cellulose in filter paper using alkyltrimethoxysilane coupled with UV radiation. The filter paper sheet was hydrophobised by immersion in an octadecyltrimethoxysilane/heptane (OTMS/heptane) solution (0.25 vol. %) containing 5 vol. % of ethyl acetate (EtOAc). The hydrophobic-hydrophilic contrast was generated on the filter paper after the hydrophobised paper sheet was exposed to UV light with a metal mask creating the desired pattern on the sheet. The exposed area was oxidised to create a hydrophilic area, while the hydrophobic area was protected by the metal mask. The optimal conditions for the fabrication of μPAD were studied; these included ethyl acetate concentration (CEtOAc), immersion time, octadecyltrimethoxysilane concentration (COTMS) and exposure time. This method is cost-effective and simple. In addition, different functional groups could be further grafted for various assay purposes. To demonstrate the feasibility of the μPAD in analytical applications, a flower-shaped μPAD with eight channels and eight detection units was fabricated and used to determine the nitrite content in pickled vegetables. The nitrite content (124 µg g−1) in the sample determined by this method compared favourably with that measured using a standard method (137 µg g−1).

Long Term Evolution (LTE) system used in High-Speed Railway (HSR) has gained the increasing attention therefore the measurements and analysis of the broadband wireless channel for the HSR communication is urgently needed. This paper focuses on the special fading characteristics of viaduct and hilly terrain scenarios based on the extensive and practical multiple input multiple output (MIMO) measurements which is conducted on Harbin-Dalian passenger dedicated railway line at 2.6 GHz with a bandwidth of 40 MHz. Here, we provide the power delay profiles as the first analytical results. Large-scale fading parameters such as path loss and shadow fading are given and discussed. As for small-scale fading, two similar but not identical K-factor models in different scenario are presented for comparison. Through the analysis on the two typical scenarios, this paper provides great guiding significance for promoting evaluation, simulation and design of the wireless communication system based on Long Term Evolution Railway (LTE-R).

An experiment was developed to demonstrate a microfluidic device in the analytical chemistry (instrumental analysis) laboratory. Students made the paper-based microfluidic device with a wax pen and a piece of filter paper and used it to determine the total quantity of amino acids in a green tea leaf extract. The device is low cost, easy-to-make, and easy-to-use. The student results compared favorably with those from standard method.

We presented a distance-based detection method for visual quantification of mercury ions on a microfluidic paper-based analytical device (μPAD). Dithizone in NaOH solution was used as chromogenic reagent and deposited onto paper channel delimited by hydrophobic wax barrier. Reactions happened between mercury ions and dithizone to form an insoluble colored complex, producing colored precipitate on the paper channel. The length of colored precipitate could be readily measured using the printed ruler along each device. The length of precipitate increase linearly with the mercury concentrations, mercury in sample solution could be quantified by measuring the length of the colored precipitate. Being free of any electronic instruments, this method has the advantages of portability, ease of use, low cost and disposability. This presented method was used to detect mercury ions in a synthetic sample, demonstrating its potential in on-site and real time analysis.

A simple and automated method for determination of ascorbic acid (AA) in complex samples by flow injection chemiluminescence (FI-CL) was presented. It is based on the inhibitory effect of ascorbic acid on the chemiluminescence reaction between luminol and hydrogen peroxide in the flow system. A home-made micro column of cation exchange resin was adapted to the FI manifold to achieve on-line removal of interference. This method was used to determine the AA content in urine samples with a detection limit of 6.03 ×10 -9 mol/L AA and recovery of 93.1-111.0%. This proposed method allows high - throughput determination of AA in urine samples without chromatographic separation, demonstrating that the FI-CL method has significant potential in determination of species in complex samples by adapting a micro column filled with various functionalized materials to the FI manifold. e-mail: cailf@zju.edu.cn INTRODUCTION Ascorbic acid, usually found in citrus fruits and vegetables, is mainly used as a cure for various diseases including scurvy, drug poisoning, liver disease and allergic reactions. Consequently, determination of ascorbic acid in foods, pharmaceuticals, and biological samples is crucial. A variety of methods have been employed for the determination of ascorbic acid in simple samples including foods, Vitamin C tablets and injections, among which iodometric method

For multiuser multiple-input multiple-output (MU-MIMO) systems with limited feedback in the downlink scenario, an end-to-end robust Tomlinson-Harashima Precoding (THP) transceiver design that incorporates receiver combining and transmit precoder is proposed based on sum mean squared error (SMSE) minimization. The channel state information (CSI) available at the transmitter for precoding is the quantized channel direction information (CDI) relayed back from each receiver using feedback bits in such system. The proposed transceiver design method is robust to the channel uncertainties arising from the quantization error and the lack of channel magnitude information (CMI). As an aside, the authors analyse the SMSE performance of the proposed algorithm. Our simulation results show that the new THP scheme outperforms the conventional precoding in limited feedback systems with respect to Bit Error Ratio (BER).

A method was developed for the rapid separation of catecholamines by nonaqueous microchip electrophoresis with LIF detection, A homemade pump-free negative pressure sampling device was used for rapid bias-free sampling in nonaqueous microchip electrophoresis, the injection time was 0.5 s and the electrophoresis separation conditions were optimized. Under the optimized conditions, the samples were separated completely in less than 1 min. The average migration times of the epinephrine, dopamine, and norepinephrine were 34.26, 43.81, and 50.07 s, with a relative standard deviation of 1.05, 1.26 and 0.89% (n = 7), respectively. The linearity of the method ranged from 0.0125 to 2.0 mg/L for epinephrine and 0.025∼4.0 mg/L for dopamine, and norepinephrine, with correlation coefficients ranging between 0.9978 and 0.9986. The detection limits of epinephrine, dopamine, and norepinephrine were 2.5, 5.0 and 5.0 μg/L, respectively. The recoveries of epinephrine, dopamine, and norepinephrine in spiked urine samples were between 86 and 103%, with relative standard deviations of 4.5∼6.8% (n = 5). The proposed nonaqueous microchip electrophoresis with laser induced fluorescence detection system combined with a pump-free negative pressure sampling device was a simple, inexpensive, energy efficient, miniaturized system that can be successfully applied for the determination of catecholamines in urine samples. This article is protected by copyright. All rights reserved.

A novel microfluidic device integrated with continuous introduction of individual cells and detection of intracellular reducing species by laser induced fluorescence (LIF) detector is reported. A single channel with one sheath-flow channel located on each side of the sampling channel was designed. The intracellular reducing species were derivatized by a newly synthesized 2,2,6,6-tetramethyl-piperidine-1-oxyl (TEMPO)-based fluorescent probe. The labeled cells were hydrodynamically focused by sheath-flow streams and sequentially introduced into the sampling channel under hydrostatic pressure generated by adjusting liquid levels in the reservoirs. Intracellular reducing level in intact living L02 cells was detected by LIF without cytolysis. Upon stimulation with 100 µmol L-1 hydrogen peroxide for 30 min, the intracellular reducing level decreased in response to oxidative stress. A throughput of 41-44 cells min-1 was obtained. Um novo dispositivo microfluídico integrado com introdução contínua de células individuais e detecção de espécies redutoras intracelulares por detector de fluorescência induzida por laser (LIF) é relatado. Um canal central de amostragem foi desenhado sendo flanqueado por dois outros canais auxiliares. As espécies intracelulares redutoras foram derivadas por uma sonda fluorescente baseada na recém-sintetizada 2,2,6,6-tetrametil-piperidina-1-oxilo (TEMPO). As células marcadas foram hidrodinamicamente focadas pelas correntes da bainha de fluxo e sequencialmente introduzidas no canal de amostragem sob pressão hidrostática gerada por ajuste dos níveis de líquido nos reservatórios. O nível de redução intracelular em células vivas intactas L02 foi detectada por LIF sem citólise. Após estimulação com 100 mmol L-1 de peróxido de hidrogênio, durante 30 minutos, o nível de redução intracelular diminuiu em resposta ao estresse oxidativo. Foi obtida uma taxa de transferência de 41-44 células min-1.

In this paper, we implement a prototype of smart-home system based on the IPv6 over Low power Wireless Personal Area Networks, 6LoWPAN. The seamless connection is built between the wireless sensor networks (WSNs) and the Internet, which makes users visit the smart-home system through other IP-based networks. We also implement a routing protocol based on AODV-jr and embed it into 6LoWPAN. Imote2 platforms are used to verify our system. Meanwhile, this system provides a user-friendly interface to monitor and control the whole system by using web service technology. Furthermore, the system can be deployed easily and experimental results show that the design of our smart-home system can be served timely and reliably.