Detection of G-quartet structure in a DNA aptamer stationary phase using a fluorescent dye

The fluorescent porphyrin dye N-methylmesoporphyrin IX (NMM) was used to provide direct evidence of intramolecular G-quartet formation by an oligonucleotide immobilized at the inner surface of a fused silica capillary. The oligonucleotide is the thrombin-binding DNA aptamer, which has been used in several analytical applications, including a stationary phase for open tubular capillary electrochromatography. Spectroscopic studies of the dye in batch solutions of the aptamer and of an oligonucleotide with the same base composition, but in a different, "scrambled" sequence that does not form an intramolecular G-quartet, provided evidence of selective fluorescence enhancement of NMM by the aptamer in the intramolecular G-quartet structure. On-column experiments compared results for injections of NMM onto an aptamer-coated capillary, a capillary coated with the scrambled sequence oligonucleotide, and a bare fused silica capillary. Results show that while NMM adsorbs to both coated capillaries, the selective fluorescence enhancement provides evidence of the intramolecular G-quartet structure on the aptamer-coated capillary.     

Controlled mixing in microfluidic systems using bacterial chemotaxis

We demonstrate the use of Escherichia coli and their chemotactic characteristics to enhance mixing in a microchannel in a controlled and bi-directional manner. The presence of a chemoattractant in one arm of a three-junction microchannel results in an asymmetric increase in the effective diffusion coefficient of extremely high molecular weight TMR-Dextran (MW 2 000 000), which rises linearly with the concentration of attractant from a baseline value of 8-42 microm(2)/s at a concentration of 0.1 M. The response to a repellent is similar, with the opposite bias.     

水性聚氨酯-分散荧光黄高分子荧光染料的合成与荧光特性

用聚氧化丙烯二醇、2,4-甲苯二异氰酸酯、二羟甲基丙酸、三乙胺和分散荧光黄(DFY)合成了一种新型的水性聚氨酯-分散荧光黄(PU-DFY)高分子荧光染料.红外和紫外-可见吸收光谱显示,DFY已被化学键入聚氨酯链中.荧光光谱表明,PU-DFY和DFY都可在507nm处发出较强荧光,且很低浓度PU-DFY发出的荧光都较高浓度DFY的强.研究还发现,加入二苯胺猝灭剂的PU-DFY,荧光强度随温度的升高而增强,与一般荧光物质荧光强度的温度特性相反.     

Velocity measurement of particles flowing in a microfluidic chip using Shah convolution Fourier transform detection

A noninvasive radiative technique, based on Shah convolution Fourier transform detection, for velocity measurement of particles in fluid flows in a microfluidic chip, is presented. It boasts a simpler instrumental setup and optical alignment than existing measurement methods and a wide dynamic range of velocities measurable. A glass-PDMS microchip with a layer of patterned Cr to provide multiple detection windows which are 40 microns wide and 70 microns apart is employed. The velocities of fluorescent microspheres, which were electrokinetically driven in the channel of the microfluidic chip, were determined. The effects of increasing the number of detection windows and sampling period were investigated. This technique could have wide applications, ranging from the determination of the velocity of particles in pressure-driven flow to the measurement of electrophoretic mobilities of single biological cells.     

Electrochemical impedance measurement of prostate cancer cells using carbon nanotube array electrodes in a microfluidic channel

Highly aligned multi-wall carbon nanotubes were synthesized in the shape of towers and embedded into fluidic channels as electrodes for impedance measurement of LNCaP human prostate cancer cells. Tower electrodes up to 8 mm high were grown and easily peeled off a silicon substrate. The nanotube electrodes were then successfully soldered onto patterned printed circuit boards and cast into epoxy under pressure. After polishing the top of the tower electrodes, RF plasma was used to enhance the electrocatalytic effect by removing excess epoxy and activating the open end of the nanotubes. Electrodeposition of Au particles on the plasma-treated tower electrodes was done at a controlled density. Finally, the nanotube electrodes were embedded into a polydimethylsiloxane (PDMS) channel and electrochemical impedance spectroscopy was carried out with different conditions. Preliminary electrochemical impedance spectroscopy results using deionized water, buffer solution, and LNCaP prostate cancer cells showed that nanotube electrodes can distinguish the different solutions and could be used in future cell-based biosensor development.     

Temperature field of a plate with internal temperature-dependent heat source

The problem of asymmetric heating of a plate is considered in a medium with variable temperature in the presence of an internal heat source, the power of which is dependent on temperature and time.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 41, No. 5, pp. 901–905, November, 1981.     

Recent developments and patents on biological sensing using nanoparticles in microfluidic systems

Microfluidic systems provide a total solution of biological and chemical analysis from the sample application to the display of the analysis results. A lot of developments on the point-of-care diagnostic applications have been reported and the commercial possibility is shown. To achieve sensitive and specific biological sensing, nanoparticles may provide a promising tool because they have similar length scale with the biomolecules. The nano-sensing technology suggests a molecular level detection of the biomolecules to pursue higher performance. In this review, recent developments and patents on the biological sensing using nanoparticles in microfluidic systems are discussed. An updated, systematic and rapid reference in the field of nano-biological sensing is provided.     

Analysis of temperature-dependent magnetization in Sm-Fe-Ccompounds using a two-sublattice model

The temperature dependence of magnetization in Sm₃Fe ₂₀C_x (x =0.3, 0.6, 0.8) and Sm₂Fe_16.5C_1.0 intermetallic compounds with rhombohedral structure has been analyzed using molecular field theory. On the basis of a two-sublattice model, the molecular field coefficients are calculated using a numerical fitting method. The Curie temperature and the Fe-Fe, Sm-Fe, Sm-Sm magnetic interaction energies for the compounds are determined from these coefficients. The results show that the increase of the Curie temperature (T_c) with the increase of carbon content x is attributed mainly to the enhancement of the Fe-Fe exchange interaction energy caused by carbon atoms added     

Temperature and velocity measurement fields of fluids using a schlieren system

This paper proposes a combined method for two-dimensional temperature and velocity measurements in liquid and gas flow using a schlieren system. Temperature measurements are made by relating the intensity level of each pixel in a schlieren image to the corresponding knife-edge position measured at the exit focal plane of the schlieren system. The same schlieren images were also used to measure the velocity of the fluid flow. The measurement is made by using particle image velocimetry (PIV). The PIV software used in this work analyzes motion between consecutive schlieren frames to obtain velocity fields. The proposed technique was applied to measure the temperature and velocity fields in the natural convection of water provoked by a heated rectangular plate.     

Hydrogel-based microreactors as a functional component of microfluidic systems

A simple two-step method for fabricating poly(ethylene glycol) (PEG) hydrogel-based microreactors and microsensors within microfluidic channels is described. The intrachannel micropatches contain either a dye, which can report the pH of a solution within a fluidic channel, or enzymes that are able to selectively catalyze specific reactions. Analytes present within the microfluidic channel are able to diffuse into the micropatches, encounter the enzymes, and undergo conversion to products, and then the products interact with the coencapsulated dye to signal the presence of the original substrate. The micropatches are prepared by photopolymerizing the PEG precursor within the channel of a microfluidic system consisting of a poly(dimethylsiloxane) mold and a glass plate. Exposure takes place through a slit mask oriented perpendicular to the channel, so the size of the resulting micropatch is defined by the channel dimensions and the width of the slit mask. Following polymerization, the mold is removed, leaving behind the micropatch(es) atop the glass substrate. The final microfluidic device is assembled by irreversibly binding the hydrogel-patterned glass slide to a second PDMS mold that contains a larger channel. Multiple micropatches containing the same or different enzymes can be fabricated within a single channel. The viability of this approach is demonstrated by sensing glucose using micropatches copolymerized with glucose oxidase, horseradish peroxidase, and a pH-sensitive dye.     

Improved amplified spontaneous emission by doping of green fluorescent dye C545T in red fluorescent dye DCJTB:PS polymer films

Amplified spontaneous emission (ASE) characteristics of a red fluorescent dye, 4-(dicy-anomethylene)-2-t-butyl-6(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB), and a green fluorescent dye, (10-(2-benzothiazolyl)-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H,11H-[1] benzopyrano [6,7,8-ij]quinolizin-11-one) (C545T) codoped polystyrene (PS) as the active medium were studied. It was found that the performance of ASE is greatly improved due to the introduction of C545T. By optimizing the concentrations of C545T and DCJTB in PS, an ASE threshold of 0.016 mJ pulse(-1), net gain of 52.71 cm(-1), and loss of 11.7 cm(-1) were obtained. The efficient F?rster energy transfer from C545T to DCJTB was used to explain the improvement of the ASE performance in the coguest system.     

Mapping spatiotemporal molecular distributions using a microfluidic array

The spatial and temporal distributions of an extensive number of diffusible molecules drive a variety of complex functions. These molecular distributions often possess length scales on the order of a millimeter or less; therefore, microfluidic devices have become a powerful tool to study the effects of these molecular distributions in both chemical and biological systems. Although there exist a number of studies utilizing microdevices for the creation of molecular gradients, there are few, if any, studies focusing on the measurement of spatial and temporal distributions of molecular species created within the study system itself. Here we present a microfluidic device capable of sampling multiple chemical messengers in a spatiotemporally resolved manner. This device operates through spatial segregation of nanoliter-sized volumes of liquid from a primary sample reservoir into a series of analysis microchannels, where fluid pumping is accomplished via a system of passive microfluidic pumps. Subsequent chemical analysis within each microchannel, achieved via optical or bioanalytical methods, yields quantitative data on the spatial and temporal information for any analytes of interest existing within the sample reservoir. These techniques provide a simple, cost-effective route to measure the spatiotemporal distributions of molecular analytes, where the system can be tailored to study both chemical and biological systems.     

Method for microfluidic whole-chip temperature measurement using thin-film poly(dimethylsiloxane)/rhodamine B

A novel method is presented for on-chip temperature measurements using a poly(dimethylsiloxane) (PDMS) thin film dissolved with Rhodamine B dye. This thin film is sandwiched between two glass substrates (one of which is 150 microm thick) and bonded to a microchannel molded in a PDMS substrate. Whole-chip (liquid and substrate) temperature measurements can be obtained via fluorescent intensity visualization. For verification purposes, the thin film was tested with a tapered microchannel subjected to Joule heating, with resulting axial temperature gradients comparing well with numerical simulations. Errors induced by the definite film thickness are discussed and accounted for during experimental and analytical analysis. Alternative validation using the traditional in-channel Rhodamine B injection method was also attempted. The thin film has several advantages over traditional methods. First, false intensity readings due to adsorption and absorption of Rhodamine B into PDMS channels are eliminated. Second, whole-chip temperature measurements are possible. Third, separation of working liquid from Rhodamine B dye prevents possible electrophoresis effects.     

荧光标记壳聚糖的反应动力学研究

壳聚糖的荧光标记是研究壳聚糖在体内的分布、降解和吸收的重要方法之一.荧光素异硫氰酸酯(FITC)是一种常用的荧光染料.本文考察了FITC与壳聚糖氨基反应时,溶液pH值、FITC溶剂以及温度对反应动力学的影响,以期建立一种快速、稳定的制备荧光标记壳聚糖的方法.结果表明随着pH值增大,反应加快,但＞7.7时,则对反应无影响;甲醇作为FITC的溶剂时反应速度大于PBS;随着反应温度的升高,反应速度也随之加快.     

Promising fluorescent dye for solar energy conversion based on a perylene perinone

We describe the synthesis of a dye based on a perylene perinone and evaluate its potential as the functional material for use in the luminescent solar concentrator (LSC). The dye extends the absorption wavelength of LSCs using the perylene-based dye Lumogen Red 305 by more than ~50 nm, translating into the collection of potentially 25% more photons at a reasonable fluorescent quantum yield and photostability. When the new perinone is used in a two-waveguide LSC in conjunction with Red 305, the integrated edge emission of the total LSC system may be increased more than 24% when compared to the Red 305 dye alone.     

Temperature and heat spectrum measurement using mathematical statistic apparatus

A nonconventional method of temperature measurement is observed, where no information about heated surface emissivity is required. Main principles of simultaneous spectrum and temperature measurement via ratio pyrometry are described. Measurement device optical scheme and results of blackbody and colored body simulators’ radiation temperature measurements are given. Comparison of emissivity of colored body simulators and optical transmission coefficient of glasses used for simulation is conducted.     

Temperature measurement in a reduced-pressure subsonic oxygen jet

An induction plasmotron has been used to produce a stream of oxygen plasma, whose temperature distributions in the axial and radial directions have been measured at low pressure.Translated from Inzhenerno-fizicheskii Zhurnal, No. 2, pp. 318–321, February, 1991.     

Lensfree sensing on a microfluidic chip using plasmonic nanoapertures

We demonstrate lensfree on-chip sensing within a microfluidic channel using plasmonic nanoapertures that are illuminated by a partially coherent quasimonochromatic source. In this approach, lensfree diffraction patterns of metallic nanoapertures located at the bottom of a microfluidic channel are recorded using an optoelectronic sensor-array. These lensfree diffraction patterns can then be rapidly processed, using phase recovery techniques, to back propagate the optical fields to an arbitrary depth, creating digitally focused complex transmission patterns. Cross correlation of these patterns enables lensfree on-chip sensing of the local refractive index surrounding the near-field of the plasmonic nanoapertures. Based on this principle, we experimentally demonstrate lensfree sensing of refractive index changes as small as ～2×10(-3). This on-chip sensing approach could be quite useful for development of label-free microarray technologies by multiplexing thousands of plasmonic structures on the same microfluidic chip, which can significantly increase the throughput of sensing.