The extension of chromosomal DNA is a key technique in high-resolution gene location such as extended fibre fluorescent in situ hybridization. In this paper, we propose a new micro-device designed for on-chip integration of three functions, (1) positioning of cells, (2) extending chromosomal DNA from the cells, and (3) anchoring the extended DNA fibres. The device has a flow chamber equipped with (a) multi-phase electrodes to create electroosmotic flow (EOF) of variable direction, (b) a set of micro-fabricated pocket-like structures for cell positioning, and (c) a micro-pillar array whose surface is chemically modified to anchor DNA fibres. First, unidirectional EOF is induced, by which cells are carried into the micro-pockets and positioned, one cell at each pocket. After rupturing the cells, chromosomal DNA from each cell is hydrodynamically extended by EOF. When the EOF direction is rotated through 90°, the fibres are made to contact with the pillars to be anchored. Because the velocity of the EOF is controllable, the breakage of DNA during the process can be minimized. Thus immobilized DNA fibres are suspended a few microns above the surface, allowing free access of probe molecules.

In living tissues, a cell is exposed to chemical substances delivered partially to its surface. Such a heterogeneous chemical environment potentially induces cell polarity. To evaluate this effect, we developed a microfluidic device that realizes spatially confined delivery of chemical substances at subcellular resolution. Our microfluidic device allows simple setup and stable operation for over 4 h to deliver chemicals partially to a single cell. Using the device, we showed that subcellular glucose exposure triggers an intracellular [Ca2+] change in the β-cells. In addition, the imaging of a cell expressing GFP-tagged insulin showed that continuous subcellular exposure to glucose biased the spatial distribution of insulin granules toward the site where the glucose was delivered. Our approach illustrates an experimental technique that will be applicable to many biological experiments for imaging the response to subcellular chemical exposure and will also provide new insights about the development of polarity of β-cells.

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We have developed a simple technique for detecting protein in raw blood samples using size-exclusion surface plasmon resonance (SPR) sensing.

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