two photolithography-formed microchannels. Yuan et al. used a
direct-write method to form a nanofiber across the two microchannels. The two lithography formed microchannels and the nanofiber
was then used as the mold to cast the nanoelectroporation device
(Fig. 1e, f) [6]. Gao et al. developed a device to capture and apply
nanoelectroporation to an array of cells. This device was fabricated
by combine soft lithography and laser micromachining. By using a
femtosecond laser, the length of the microchannels was cut to
50 μm from the original 3000 μm (Fig. 1g) [7]. By reducing the
length of the microchannels, the cell encapsulation efficiency was
increased from 10% to 80% (Fig. 1h) [7].
In this protocol, a microfluidic platform that integrates centrifugal forced based cell trapping and nanochannel electroporation is
introduced. This platform includes a multichannel NEP biochip
and a centrifugal-force-cell-trapping encapsulation and holder. The
multichannel NEP device is fabricated through mold fabrication,
soft lithography, a DNA combing and imprinting (DCI), and sealing processes. The encapsulation and hold are fabricated through a
micromilling process. By using centrifuge force, a maximum 90%
cell trapping rate was achieved by using this platform. Each trapped
single cell was positioned on the tip of a single nanochannel for
sequential micro/nanoelectroporation. After NEP gene delivery,
these cells were able to be incubated inside this biocompatible
microenvironment for in vitro growth or moved out for further
analysis.
2 Materials and Equipment
2.1 Biochip
Fabrication
1. SU-8 photoresist, MicroChem, USA.
2. Silicon wafer.
3. Sylgard 184 poly(dimethyl siloxane) (PDMS), Dow
Corning, USA.
4. Cal thymus DNA, 75 kbp, USB Co.
5. NaCl solution, 5 wt%.
6. Glass cover slide.
7. E-Beam evaporator, Denton DV-502A, Denton Vacuum LLC.
8. 1,4-Butanediol diacrylate (1,4-BDDA), Sigma-Aldrich.
9. Irgacure 651 photoinitiator.
10. UV light, 365 nm, 30 mW.
11. Nitrogen gas.
12. Gold etchant, GE8111, Transene Company Inc., Danvers,
MA, USA.
13. Plasma surface oxygen treatment machine.
Micromachining of Polymeric Microfluidic Micro/Nanoelectroporation Device
23
direct-write method to form a nanofiber across the two microchannels. The two lithography formed microchannels and the nanofiber
was then used as the mold to cast the nanoelectroporation device
(Fig. 1e, f) [6]. Gao et al. developed a device to capture and apply
nanoelectroporation to an array of cells. This device was fabricated
by combine soft lithography and laser micromachining. By using a
femtosecond laser, the length of the microchannels was cut to
50 μm from the original 3000 μm (Fig. 1g) [7]. By reducing the
length of the microchannels, the cell encapsulation efficiency was
increased from 10% to 80% (Fig. 1h) [7].
In this protocol, a microfluidic platform that integrates centrifugal forced based cell trapping and nanochannel electroporation is
introduced. This platform includes a multichannel NEP biochip
and a centrifugal-force-cell-trapping encapsulation and holder. The
multichannel NEP device is fabricated through mold fabrication,
soft lithography, a DNA combing and imprinting (DCI), and sealing processes. The encapsulation and hold are fabricated through a
micromilling process. By using centrifuge force, a maximum 90%
cell trapping rate was achieved by using this platform. Each trapped
single cell was positioned on the tip of a single nanochannel for
sequential micro/nanoelectroporation. After NEP gene delivery,
these cells were able to be incubated inside this biocompatible
microenvironment for in vitro growth or moved out for further
analysis.
2 Materials and Equipment
2.1 Biochip
Fabrication
1. SU-8 photoresist, MicroChem, USA.
2. Silicon wafer.
3. Sylgard 184 poly(dimethyl siloxane) (PDMS), Dow
Corning, USA.
4. Cal thymus DNA, 75 kbp, USB Co.
5. NaCl solution, 5 wt%.
6. Glass cover slide.
7. E-Beam evaporator, Denton DV-502A, Denton Vacuum LLC.
8. 1,4-Butanediol diacrylate (1,4-BDDA), Sigma-Aldrich.
9. Irgacure 651 photoinitiator.
10. UV light, 365 nm, 30 mW.
11. Nitrogen gas.
12. Gold etchant, GE8111, Transene Company Inc., Danvers,
MA, USA.
13. Plasma surface oxygen treatment machine.
Micromachining of Polymeric Microfluidic Micro/Nanoelectroporation Device
23