Annual Report of Cosmetology vol.18, 2010
Synopsis of Original Research Paper

Fabrication of microfluidic devices for the productionof monodisperse liposomes and the fusion of cells
Shoji Takeuchi
Institute of Industrial Science, The University of Tokyo

This report describes a method for preparation of monodisperse giant liposomes frompatterned lipid films using electroformation. The lipid films were patterned successfully on an
indium tin oxide (ITO) electrode by a Parylene lift-off process. We found that the coefficient ofvariation (CV) of diameters of liposomes improved from 34 % to 7.6 % by using the patterned
lipid films for liposome formation.
Giant liposomes (10 - 100 μm in diameter) are cell-sized spherical lipid membranes andcan enclose bio-functional materials (e.g DNA, proteins); they can be used as an artificial
cell or biological reactor. In our previous work, we have succeeded in enclosing different
types of nano/micro materials in giant liposomes efficiently using microfluidic channels
with electroformation method. In order to control the volume of materials enclosed in theliposomes, it is important to prepare uniform-sized liposomes. The size is also an importantfactor determining the success for cell-liposome fusions. Micro-contact printing of lipids using
PDMS stamp to achieve size control of liposomes was reported. However, in general, PDMS
tends to swell when in contact with organic solvents. Here, we have used a Parylene sheet
instead of PDMS for preparing lipid patterns in order to avoid such a swelling problem. Also,
the Parylene sheet has advantages that it can be patterned by standard photolithography andpeeled off from the substrate easily.
Two indium tin oxide (ITO) glasses were used as electrodes and separated by a silicone
spacer chamber filled with degassed water. The lipid films were patterned on the bottom ITO
glass using a Parylene sheet. When AC signal (10 Hz, 0.5-2.5 Vpp) was applied to the top
and bottom ITO electrodes, the giant liposomes were formed from the patterned lipid films.
Fluorescent images of the lipids with squares of 20 μm showed clear edges of the patterned
lipids on the ITO glass. Patterned lipids of 50 x 50 μm2 square swelled and became round after
applying electric field.
The size of the liposomes became lager as the size of patterned lipid films increased. Whenthe liposomes were produced without the patterned lipid films, the size of the liposomes werewidely distributed (CV = 34 %). In contrast, our preliminary experiment shows that the CV
became narrow to 7.6 % when the patterned lipid films were used. These results imply that
this method — electroformation of giant liposomes from lipid patterns — is useful to produce
uniform-sized giant liposomes.
Finally we fabricate a device that combines microfluidic and electrical manipulation of cells
or artificial vesicles in order to perform well controlled electrofusion. The actual device allows
immobilizing cells or vesicles by suction onto an array of microholes and aligning different
vesicles over the holes by dielectrophoresis.
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