Electro cell fusion has significant potential as a biotechnology tool with applications ranging from antibody production
to cellular reprogramming. However due to low fusion efficiency of the conventional electro fusion methodology the
true potential of the technique has not been reached. In this paper, we report a new method which takes cell fusion
efficiency two orders magnitude higher than the conventional electro fusion method. The new method, based on one-toone
pairing, fusion and selection of fused cells was developed using a microfabricated device. The device was composed
of two microfluidic channels, a micro slit array and a petri dish integrated with electrodes. The electrodes positioned in
each channel were used to generate electric field lines concentrating in the micro slits. Cells were introduced into
channels and brought in to contact through the micro slit array using dielectrophoresis. The cells in contact were fused by
applying a DC pulse to electrodes. As the electric field lines were concentrated at the micro slits the membrane potential
was induced only at the vicinity of the micro slits, namely only at the cell-cell contact point. This mechanism assured the
minimum damage to cells in the fusion as well as the ability to control the strength and location of induced membrane
potential. We introduced mouse embryonic stem cells and mouse embryonic fibroblasts to the microfluidic channels and
demonstrated high-yield fusion (> 80%). Post-fusion study showed the method can generate viable hybrids of stem cells
and embryonic fibroblasts. Multinucleated hybrid cells adhering on the chip surface were routinely obtained by using
this method and on-chip culturing.
This paper presents a novel method for manipulating single chromosomal DNA, which is intended for the use in highresolution
genomic studies. Such operations as translocation, winding and unwinding of single DNA fiber are achieved
using optically-driven micro-fabricated structures, including micro-hooks and micro-bobbins for picking-up and winding
DNA, with a typical dimension of several μm. The geometry of the laser-manipulated micro-structures is designed in
such a way that a spontaneous orientation occurs with its major axis parallel to the laser beam and accepts a DNA fiber.
While monitoring under a fluorescence microscope, yeast chromosomal DNA is first extended to the full length by
electroosmotic flow. Then the micro-hooks are dispensed in the solution, and a DNA fiber is picked up with the microhook
which is driven by a focused laser beam, to separate the targeted DNA from the others. The winding is achieved
with a pair of micro-bobbins. The laser is split into two, the first beam being fixed, and the second movable circularly
around the first. When the bobbins are made into contact with DNA and revolving motion started, the fiber is wound and
suspended between them. The unwinding can be achieved just by reversing the revolving motion.
In this report, we describe a noninvasive methodology for manipulating single Mb-size whole-genome DNA molecules. Cells were subjected to osmotic shock and the genome DNA released from the burst cells was transferred to a region of higher salt concentration between cover slips using optical tweezers. The transferred genome DNA exhibits a conformational transition from a compact state into an elongated state, accompanied by the change in its environment. Here, the applicability of optical tweezers to the on-site manipulation of giant genomic DNA is suggested. Next, to control the field environment more precisely, a flow chamber was made and similar investigations were carried out. In the flow chamber, the higher-order structure of individual chromosomal DNA molecules from a fission yeast that were folded by polyamine was changed to a partially unfolded form by transporting into a higher salt condition using optical tweezers. These promising methodologies demonstrated here may make it possible to recover an intact single whole-genome DNA from a cell and carry out further sequential investigations under a microscope.