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Automatic Single-Cell Transfer Module
production of mammalian embryos. In addition to these vital concepts, cell
fusion and nuclear transplantation (Skelley, Kirak, and Suh 2009; Yia et al.
2006) are important topics. Our project “Automated Nuclear Transplantation
Using Micro Robotics” is a novel approach to finding a solution to overcome
difficulties in the nuclear transplantation process. In this project, several
cell manipulation tasks such as positioning, cutting, sorting, filtering, and
fusion are performed by different interconnected modules using a so-called
desktop bioplant (Arai et al. 2007). This desktop bioplant, which includes
microchannels and microwells on a chip with appropriate sensors and
actuators, is increasingly in demand for nuclear transplantation operations
in biotechnology.
Microfluidic methodologies, however, have suffered from limited means to
manipulate fluids and cells. In conventional methods, the single-cell transfer and control from a container to a polydimethylsiloxane (PDMS) microfluidic chip is carried out by the aid of a micropipette suction and manual
on-chip stream manipulation by a pump. Biological cells must be picked
up from the container one by one under the view of a microscope and supplied to the microfluidic chip, where single-cell operations are performed.
For each single cell, an operator should repeat the same method until the
desired number of cells is collected. Although this process is relatively easy
for large cells (i.e., oocyte ~100 μm), it is infeasible for small cells (i.e., fibroblast ~15 μm). A skilled operator is required for such time-consuming applications. Moreover, if the pump speed does not synchronize with the manual
cell supply process, bubble formation can be observed in the flow stream,
which is harmful to living cells. Once the desired number of cells is delivered into the microchannel, they need to be brought into the operation area
one by one. In addition, the distance between consecutive cells cannot be
maintained in the microchannel by manual methods. The principle behind
our proposed solution is to accomplish all of these functions (cell suction,
transportation, on-chip position control, observation, and cell supply) automatically with one integrated system. For example, in the case of the cell
fusion step of mammalian cloning, a microfluidic chip requires simultaneous control of the cells involved. In this process, two cells (a donor cell and
an oocyte) are brought into very close contact and aligned via alternating
current (AC), after which a direct current (DC) is applied for a brief period
to complete the fusion (MacDonald, Spalding, and Dholakia 2003; Walker,
Zeringu, and Beebe 2004). Precise cell supply and transportation are essential when performing such an operation. This has significant advantages for
some microfluidic cell applications such as on-chip micro-injection (Andrea
and Klavs 2008), on-chip single-cell polymerase chain reaction (PCR; Toriello
et al. 2008), and cell encapsulation with microfluidic droplets (He, Edgar, and
Jeffries 2005). Moreover, due to the importance of the information gathered
by individual cells, several analytical techniques for chemical analysis of single cells have been proposed by different groups. These techniques include
capillary electrophoresis (Huang et al. 2008; Wu, Wheeler, and Zare 2004)
Automatic Single-Cell Transfer Module
production of mammalian embryos. In addition to these vital concepts, cell
fusion and nuclear transplantation (Skelley, Kirak, and Suh 2009; Yia et al.
2006) are important topics. Our project “Automated Nuclear Transplantation
Using Micro Robotics” is a novel approach to finding a solution to overcome
difficulties in the nuclear transplantation process. In this project, several
cell manipulation tasks such as positioning, cutting, sorting, filtering, and
fusion are performed by different interconnected modules using a so-called
desktop bioplant (Arai et al. 2007). This desktop bioplant, which includes
microchannels and microwells on a chip with appropriate sensors and
actuators, is increasingly in demand for nuclear transplantation operations
in biotechnology.
Microfluidic methodologies, however, have suffered from limited means to
manipulate fluids and cells. In conventional methods, the single-cell transfer and control from a container to a polydimethylsiloxane (PDMS) microfluidic chip is carried out by the aid of a micropipette suction and manual
on-chip stream manipulation by a pump. Biological cells must be picked
up from the container one by one under the view of a microscope and supplied to the microfluidic chip, where single-cell operations are performed.
For each single cell, an operator should repeat the same method until the
desired number of cells is collected. Although this process is relatively easy
for large cells (i.e., oocyte ~100 μm), it is infeasible for small cells (i.e., fibroblast ~15 μm). A skilled operator is required for such time-consuming applications. Moreover, if the pump speed does not synchronize with the manual
cell supply process, bubble formation can be observed in the flow stream,
which is harmful to living cells. Once the desired number of cells is delivered into the microchannel, they need to be brought into the operation area
one by one. In addition, the distance between consecutive cells cannot be
maintained in the microchannel by manual methods. The principle behind
our proposed solution is to accomplish all of these functions (cell suction,
transportation, on-chip position control, observation, and cell supply) automatically with one integrated system. For example, in the case of the cell
fusion step of mammalian cloning, a microfluidic chip requires simultaneous control of the cells involved. In this process, two cells (a donor cell and
an oocyte) are brought into very close contact and aligned via alternating
current (AC), after which a direct current (DC) is applied for a brief period
to complete the fusion (MacDonald, Spalding, and Dholakia 2003; Walker,
Zeringu, and Beebe 2004). Precise cell supply and transportation are essential when performing such an operation. This has significant advantages for
some microfluidic cell applications such as on-chip micro-injection (Andrea
and Klavs 2008), on-chip single-cell polymerase chain reaction (PCR; Toriello
et al. 2008), and cell encapsulation with microfluidic droplets (He, Edgar, and
Jeffries 2005). Moreover, due to the importance of the information gathered
by individual cells, several analytical techniques for chemical analysis of single cells have been proposed by different groups. These techniques include
capillary electrophoresis (Huang et al. 2008; Wu, Wheeler, and Zare 2004)