We demonstrate the accommodation of log-scale concentration gradients of inhibitors on a single microfluidic chip with a semi-direct dilution capability of reagents for the determination of the half-inhibitory concentration or IC50. The chip provides a unique tool for hosting a wide-range of concentration gradient for studies that require an equal distribution of measuring points on a logarithmic scale. Using Matrix metalloproteinase IX and three of its inhibitors, marimastat, batimastat and CP471474, we evaluated the IC50 of each inhibitor with a single experiment. The present work could be applied to the systematic study of biochemical binding and inhibition processes particularly in the field of mechanistic enzymology and the pharmaceutical industry.

In this study, the blood cell clogging phenomenon occurring in blood separators based on capillary action is carefully investigated and how to minimize the reduction in plasma separation speed caused by clogging is discussed. Four different blood separators are fabricated on optically transparent glass substrates to clearly observe the blood plasma separation and the blood cell clogging in the microfluidic devices. Each separation experiment is captured by a high-speed video camera. The captured images are analyzed using a theoretical model proposed in this study to quantify the effect of the microstructure on the degree of blood cell clogging. Finally, design guidelines for the microstructure of the micro blood separator are discussed based on the analysis.

A late-flowering transgenic radish has been produced by the expression of an antisense GIGANTEA (GI) gene fragment using a floral-dip method. Twenty-five plants were dipped into a suspension of Agrobacterium carrying a 2.5 kb antisense GI gene fragment from Arabidopsis, along with the gusA and bar reporter genes, all under the control of a CaMV 35S promoter. From a total of 1462 seeds harvested from these floral-dipped plants, 16 Basta-resistant T1 plants were found to have GUS activity (transformation efficiency of 1.1%). Southern analysis confirmed the integration of one or two copies of the gusA gene in these herbicide-resistant plants. Expression of the GI gene in T1 plants was much reduced compared to both wildtype plants and plants transformed with pCAMBIA3301 (positive control). In the progenies of eleven T1 plants analysed (T2 generation), all lines showed a significant delay in both bolting and flowering times compared to wildtype and positive control plants, and that, the level of GI transcript was inversely proportional to the time of bolting and flowering. At a maximum, bolting and flowering times were delayed by 17 and 18 days respectively, compared to wildtype plants (in positive control plants, the delay was 23 and 26 days, respectively). Ten of the 11 lines exhibited a significant reduction in plant height compared to wildtype and positive control plants. This study provides evidence that down-regulation of the GI gene by co-suppression could delay bolting in a cold-sensitive long-day (LD) plant. Production of late-flowering germplasms of radish may allow this important crop to be cultivated over an extended period and also provide further food to the famine countries of S/E Asia.

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This paper describes a novel technology-an electric field isolator (EFI)-that can be used for achieving isolated and electrophoretic manipulation of charged biomolecules inside a selected microscopic location. The EFI is a ground ring-shaped electrode (RE) surrounding a centre electrode (CE), which is comprised of a functional unit. When the CE is powered, the ground RE can inhibit the electric field from spreading to the neighbouring functional units. Therefore, the electrophoretic movement of the charged molecules in an electric field, which is based on the principle similar to that of electrophoresis, can be isolated inside a selected location. The ground RE causing this phenomenon is referred to as the EFI. In this paper, we clearly show the functionality of the EFI with mathematical and experimental studies.