Power-free poly(dimethylsiloxane) microfluidic devices for gold nanoparticle-based DNA analysis

An extremely simple, power-free pumping method for poly(dimethylsiloxane)(PDMS) microfluidic devices is presented. By exploiting the high gas solubility of PDMS, the energy for the pumping is pre-stored in the degassed bulk PDMS, therefore no additional structures other than channels and reservoirs are required. In a Y-shaped microchannel with cross section of 100 microm width x 25 microm height, this method has provided flow rate of 0.5-2 nL s(-1), corresponding to linear velocity of 0.2-0.8 mm s(-1), with good reproducibility. As an application of the power-free pumping, gold nanoparticle-based DNA analysis, which does not rely on the cross-linking mechanism between nanoparticles, has been implemented in a microchannel with three inlets. Target 15mer DNA has been easily and unambiguously discriminated from its single-base substituted mutant. Instead of colorimetric detection in a conventional microtube, an alternative detection technique suitable for microdevices has been discovered-observation of deposition on the PDMS surfaces. The channel layout enabled two simultaneous DNA analyses at the two interfaces between the three laminar streams.     

Novel synthesis of zerumbone-pendant derivatives and their biological activity

Zerumbone 1, having powerful latent reactivity and containing two conjugated double bonds and a double conjugated carbonyl group is the major component of the essential oil of wild ginger, Zingiber zerumbet Smith. The conjugation system plays an important role in the expression of biological activity. N-Bromosuccinimide (NBS) reaction of 1 gave high reactive intermediate 2 with an exo-methylene group, which was obtained from 1 quantitatively. Treatment of 2 with nucleophiles gave various zerumbone-pendant derivatives, including C–H, C–O, C–N, and C–C bond formation, maintaining the conjugation system through S_N2′-type reaction. Almost all zerumbone-pendant derivatives showed a good value of IC₅₀ against the suppressive effect of NO generation. Among them, amine derivative 5, binding with 2 mol of zerumbone, showed the strongest activity (IC₅₀: 0.24 μM).     

Colorimetric biosensors based on DNA-nanoparticle conjugates.

In this review, we present an overview of the technologies in colorimetric biosensors based on DNA-nanoparticle conjugates. Two types of DNA-nanoparticles aggregation assays are summarized. One of the methods relies on cross-linking of the gold nanoparticle (GNP) by hybridization. The crosslinking system was used not only to detect target DNA sequences, but also to detect metal ions or small molecules which were recognized by DNAzymes. The other method is the GNP non-crosslinking system. This approach shows high performance in the detection of single nucleotide polymorphisms. These methods do not need special equipment and open up a new possibility of point-of-care diagnoses.     

Phase calibration of sonar systems using standard targets and dual-frequency transmission pulses

The phase angle component of the complex frequency response of a sonar system operating near transducer resonance is usually distorted. Interpretation and classification of the received sonar signal benefits from the preservation of waveform fidelity over the full bandwidth. A calibration process that measures the phase response in addition to the amplitude response is thus required. This paper describes an extension to the standard-target calibration method to include phase angle, without affecting the experimental apparatus, by using dual-frequency transmission pulses and frequency-domain data processing. This approach reduces the impact of unknown range and sound speed parameters upon phase calibration accuracy, as target phase is determined from the relationship of the two frequency components instead of relying on a local phase reference. Tungsten carbide spheres of various sizes were used to simultaneously calibrate the amplitude and phase response of an active sonar system in a laboratory tank. Experimental measurements of target phase spectra are in good agreement with values predicted from a theoretical model based upon full-wave analysis, over an operating frequency of 50-125 kHz.     

Power-free sequential injection for microchip immunoassay toward point-of-care testing

This paper presents a simple fluid handling technique for microchip immunoassay. Necessary solutions were sequentially injected into a microchannel by air-evacuated poly(dimethylsiloxane), and were passively regulated by capillary force at the inlet opening. For heterogeneous immunoassay, microchips are potentially useful for reduction of sample consumption and assay time. However, most of the previously reported microchips have limitations in their use because of the needs for external power sources for fluid handling. In this paper, an on-chip heterogeneous immunofluorescence assay without such an external power source is demonstrated. The microchip consisting of poly(dimethylsiloxane) (PDMS) and glass has a simple structure, and therefore is suitable for single-use applications. Necessary solutions were sequentially injected into a microchannel in an autonomous fashion with the power-free pumping technique, which exploits the high solubility and the rapid diffusion of air in PDMS. For deionized water, this method yielded flow rates of 3-5 nL s-1 with reproducibility of 4-10%. The inlet opening of the microchannel functioned as a passive valve to hold the solution when the flow was finished. Rabbit immunoglobulin G (rIgG) and human C-reactive protein (CRP) were detected using the microchannel walls as reaction sites. With the sample consumption of 1 microL and the assay time of approximately 20 min including the antibody immobilization step, the sandwich immunoassay methods for rIgG and CRP exhibited the limits of detection of 0.21 nM (0.21 fmol) and 0.42 nM (0.42 fmol), respectively.     

High-bandwidth hybrid quantum repeater

We present a physical- and link-level design for the creation of entangled pairs to be used in quantum repeater applications where one can control the noise level of the initially distributed pairs. The system can tune dynamically, trading initial fidelity for success probability, from high fidelity pairs (F=0.98 or above) to moderate fidelity pairs. The same physical resources that create the long-distance entanglement are used to implement the local gates required for entanglement purification and swapping, creating a homogeneous repeater architecture. Optimizing the noise properties of the initially distributed pairs significantly improves the rate of generating long-distance Bell pairs. Finally, we discuss the performance trade-off between spatial and temporal resources.     

Hands on: thermal bonding of nano- and microfluidic chips

Microchimica Acta - Fused silica microchips have several attractive features; they are stable, transparent and allow fabrication with immense precision, also of nanochannels, which make them good...     

Combining microchip and cell technology for creation of novel biodevices

Microchip technology has matured over the years into an important field in which novel technologies are being constantly invented, and down-sizing and incorporation of already existing methodologies into the microscale is increasing assay performance and bearing the promise of future total integration for simple, widespread use. One rapidly growing sub-discipline of the microchip research field is focused around the integration of microchip technology and cell biology. In this review, we recapitulate progress here at the Kitamori laboratory in direct relation to cell and microchip technologies, and show some examples of successful integration of the two, going from controlled patterning of cells, on-chip cell culture stimulation, and cardiovascular systems on a chip, to bio-microdevices integrating cardiovascular cells and microtechnology to create novel biodevices such as biocompatible, miniature pumps.     

Separation of 2-aminobenzoic acid-derivatized glycosaminoglycans and asparagine-linked glycans by capillary electrophoresis.

A capillary electrophoresis method was developed for the analysis of oligosaccharides combined with derivatization with 2-aminobenzoic acid. Glycosaminoglycan delta-disaccharides were effectively resolved on a fused-silica capillary tube using 150 mM borate, pH 8.5, as a running electrolyte solution. This analytical method was applied to the identification of glycosaminoglycan in combination with enzymatic digestion. The separation of N-glycans or glucose-oligomers was performed with a phosphate buffer containing polyethylene glycol or borate as an electrolyte solution. This method is expected to be useful in the determination of oligosaccharide structures in a glycoprotein.     

Preparation of tripyrrane analogues from resorcinol and 2-methylresorcinol for applications in the synthesis of new benziporphyrin systems

Acid catalyzed condensation of resorcinol or 2-methylresorcinol with 2 equiv. of an acetoxymethylpyrrole gave bis(pyrrolylmethyl)benzene derivatives in moderate yields; these afforded a series of novel aromatic benziporphyrins using the MacDonald "3 + 1" methodology.