A high‐throughput dielectrophoresis‐based cell electrofusion microfluidic device

Abstract

A high-throughput cell electrofusion microfluidic chip has been designed, fabricated on a silicon-on-insulator wafer and tested for in vitro cell fusion under a low applied voltage. The developed chip consists of six individual straight microchannels with a 40-μm thickness conductive highly doped Si layer as the microchannel wall. In each microchannel, there are 75 pairs of counter protruding microelectrodes, between which the cell electrofusion is performed. The entire highly doped Si layer is covered by a 2-μm thickness aluminum film to maintain a consistent electric field between different protruding microelectrode pairs. A 150-nm thickness SiO₂ film is subsequently deposited on the top face of each protruding microelectrode for better biocompatibility. Owing to the short distance between two counter protruding microelectrodes, a high electric field can be generated for cell electrofusion with a low voltage imposed across the electrodes. Both mammalian cells and plant protoplasts were used to test the cell electrofusion. About 42-68% cells were aligned to form cell-cell pairs by the dielectrophoretic force. After cell alignment, cell pairs were fused to form hybrid cells under the control of cell electroporation and electrofusion signals. The averaged fusion efficiency in the paired cells is above 40% (the highest was about 60%), which is much higher than the traditional polyethylene glycol method (<5%) and traditional electrofusion methods (∼12%). An individual cell electrofusion process could be completed within 10 min, indicating a capability of high throughput.

A cell electrofusion microfluidic device integrated with 3D thin-film microelectrode arrays

“…1(a)) is the strongest, 11 cells are always aligned along this line, 29 as schematically shown in Fig. 1(a).…”

“…The obtained results are repeatable, and the averaged fusion efficiency of total cells loaded into the device was 43.1% 6 5.8%, which is much higher than that of the traditional polyethylene glycol method (less than 5%), 31 the traditional electrofusion methods ($ 12%), 32 and most existing microfluidic devices ($ 21%-30%). 11,29 This new device only uses electric field to achieve cell pairing and fusion without the need of extra hydrodynamic force during the cell pairing and/or the postfusion steps. The experimental procedure is simple and efficient.…”

“…The electrofusion efficiency of all cells loaded into the device is about 43.1% 6 5.8%, which is much higher than that ($ 21%-30%) obtained from the device with 3D protruding microelectrode arrays. 11,29 Although cell pearl chains with more than two cells are possible to occur, as shown in Fig. 7, multiple cell fusion could be avoided in this device.…”

“…The following parameters were used in the 3D simulations: the conductivity of the cell suspension buffer is 1.2 Â 10 À4 S/m (Eppendorf Co. Ltd.), the conductivities of the Au film, quartz glass, and Durimide 7510 are 4.56 Â 10 7 S/m, 1 Â 10 À12 S/m, and 1 Â 10 À14 S/m, respectively. 29 The Ti film is neglected because its thickness is only 5 nm, and its conductivity is very close to that of Au. The electrostatics is governed by the Laplace equation in the three-dimensional space.…”

“…The efficiency of forming cell-cell twins (70.7% 6 4.5%) obtained from the new device is much higher than that ($ 46%) using the 3D protruding microelectrode array. 29 …”