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This report describes a microfluidic chip-based method to set up a single cell culture experiment in which high-efficiency pairing and microscopic analysis of multiple single cells can be achieved.
Cell co-culture assays have been widely used for studying cell-cell interactions between different cell types to better understand the biology of diseases including cancer. However, it is challenging to clarify the complex mechanism of intercellular interactions in highly heterogeneous cell populations using conventional co-culture systems because the heterogeneity of the cell subpopulation is obscured by the average values; the conventional co-culture systems can only be used to describe the population signal, but are incapable of tracking individual cells behavior. Furthermore, conventional single-cell experimental methods have low efficiency in cell manipulation because of the Poisson distribution. Microfabricated devices are an emerging technology for single-cell studies because they can accurately manipulate single cells at high-throughput and can reduce sample and reagent consumption. Here, we describe the concept and application of a microfluidic chip for multiple single-cell co-cultures. The chip can efficiently capture multiple types of single cells in a culture chamber (~46%) and has a sufficient culture space useful to study the cells' behavior (e.g., migration, proliferation, etc.) under cell-cell interaction at the single-cell level. Lymphatic endothelial cells and oral squamous cell carcinoma were used to perform a single-cell co-culture experiment on the microfluidic platform for live multiple single-cell interaction studies.
Efficient capture of different types of single cells and providing sufficient culture space are needed for single cell co-culture experiments of multiple types of single cells1. Limiting dilution is the most commonly used method to prepare the single cells for such experiments, due to the low cost of equipment required. However, due to the Poisson distribution limitation, the maximum single cell acquisition probability is only 37%, making the experimental operation laborious and time-consuming2. In contrast, using fluorescence activated cell sorting (FACS) can overcome the Poisson distribution limitation to high-efficiently prepare single cells3. However, FACS may not be accessible to some laboratories due to expensive instrumentation and maintenance cost. Microfabricated devices have been recently developed for single cell trapping4, single cell pairing5, and single cell culture applications. These devices are advantageous based on their ability to accurately manipulate single cells6, perform high-throughput experiments, or reduce sample and reagent consumption. However, performing single-cell co-culture experiments with multiple cell types with the current microfluidic devices is still challenging due the limitation of Poisson distribution1,7,8, or inability of the devices to capture more than two types of single cells4,5,6,9,10.
For example, Yoon et al. reported a microfluidic device for cell-cell interaction study11. This device uses the probabilistic method to pair cells in one chamber. However, it can only achieve the pairing of two different cell types due to geometric restrictions in the device structure. Another report from Lee et al. demonstrated a deterministic method to capture and pair single cells12. This device is increases pairing efficiency by the deterministic method but it is limited by the prolonged operation time required to pair cells. Specifically, the second cell capture can only be performed after the first captured cell is attached to the surface after 24 h. Zhao et al. reported a droplet-based microfluidic device to capture two types of a single cell13. We can found that the droplet-based microfluidic device is still limited to the Poisson distribution and can only be used on non-attached cells, and it is not possible to change the culture solution during the cultivation process.
Previously, we have developed a microfluidic "hydrodynamic shuttling chip" that utilizes deterministic hydrodynamic forces to capture multiple types of single-cell into the culture chamber and can subsequently perform cell co-culture experiment to analyze individual cell migration behavior under cell-cell interactions14. The hydrodynamic shuttling chip comprises an arrayed sets of units that each contains a serpentine by-pass channel, a capture-site, and a culture chamber. By using the difference in flow resistance between the serpentine by-pass channel and the culture chamber, and a specially designed operation procedure, different types of single cells can be repeatedly captured into the culture chamber. Notably, the ample space of the culture chamber can not only prevent the cell from being flushed during cell capture out but also provide sufficient space for the cells to spread, proliferate and migrate, allowing for observing of live single-cell interactions. In this article, we focus on the production of this device and detailed protocol steps.
1. Fabrication of a wafer mold by soft lithography
NOTE: Mask pattern data is available in our previous publication14.
2. PDMS device preparation for multiple single cell capture
3. Preparation of a single-cell suspension
NOTE: Cell types include human lymphatic endothelial cells (LECs), human OSCC TW2.6 cells expressing WNT5B-specific shRNA (WNT5B sh4) and vector control (pLKO-GFP) which were obtained from our previous study15. Please refer to our previous publication for detailed cultivation steps.
4. Multiple single-cell capture and triple single-cell culture
The device has a three-layer structure as shown by the cross-section photograph of a cut PDMS device (Figure 1A). The first layer contains a capture-site (6.0 µm in width and 4.6 µm in height) that connects the culture chamber and the by-pass channel. The difference in flow resistance between the culture chamber and the by-pass channel causes the cells to flow into the capture position and fill the entrance of the small path. After ...
The intercellular interactions of various cells in the tumor microenvironment play an important role in the progression of the tumor17. In order to understand the mechanism of cell-cell interactions, co-culture systems are used as a common analytical method. However, multiple cell types and the heterogeneity of the cells themselves have led to experimental complexity and analytical difficulties.
The hydrodynamic shuttling chip allows multiple single-cell loading in the ...
The authors declare that they have no competing financial interests.
This work was supported by a grant from the Ministry of Science and Technology (105-2628-E-400-001-MY2), and the Ph.D. Program in Tissue Engineering and Regenerative Medicine, National Chung Hsing University and National Health Research Institutes.
Name | Company | Catalog Number | Comments |
3M Advanced Polyolefin Diagnostic Microfluidic Medical Tape | 3M Company | 9795R | |
Antibiotics | Biowest | L0014-100 | Glutamine-Penicillin-Streptomycin |
AutoCAD software | Autodesk | AutoCAD LT 2011 | Part No. 057C1-74A111-1001 |
CellTracke Blue CMAC Dye | Invitrogen | C2110 | |
CellTracker Green CMFDA Dye | Invitrogen | C7025 | |
Conventional oven | YEONG-SHIN company | ovp45 | |
Desiccator | Bel-Art Products | F42020-0000 | Space saver vacuum desiccator 190 mm white base |
DiIC12(3) cell membrane dye | BD Biosciences | 354218 | Used as a cell tracker |
DMEM-F12 medium | Gibco | 11320-082 | |
Endothelial Cell Growth Medium MV 2 | PromoCell | C-22022 | |
Fetal bovine serum Hyclone | Thermo | SH30071.03HI | |
Hamilton 700 series Glass syringe ( 0.1 ml ) | Hamilton | 80630 | 100 µL, Model 710 RN SYR, Small Removable NDL, 22s ga, 2 in, point style 2 |
Harris Uni-Core puncher | Ted Pella Inc. | 15075 | with 1.5mm inner-diameter |
Harris Uni-Core puncher | Ted Pella Inc. | 15071 | with 0.5mm inner-diameter |
Hotplate | YOTEC company | YS-300S | |
Msak aligner | Deya Optronic CO. | A1K-5-MDA | |
Oxygen plasma | NORDSON MARCH | AP-300 | |
Plasma cleaner | Nordson | AP-300 | Bench-Top Plasma Treatment System |
Polydimethylsiloxane (PDMS) kit | Dow corning | Sylgard 184 | |
Poly-tetrafluoroethene (PTFE) | Ever Sharp Technology, Inc. | TFT-23T | inner diameter, 0.51 mm; outer diameter, 0.82 mm |
Removable tape | 3M Company | Scotch Removable Tape 811 | |
Silicon wafer | Eltech corperation | SPE0039 | |
Spin coater | Synrex Co., Ltd. | SC-HMI 2" ~ 6" | |
Stereomicroscope | Leica Microsystems | Leica E24 | |
SU-8 10 negative photoresist | MicroChem | Y131259 | |
SU-8 2 negative photoresist | MicroChem | Y131240 | |
SU-8 2050 negative photoresist | MicroChem | Y111072 | |
SU-8 developer | Grand Chemical Companies | GP5002-000000-72GC | Propylene glycol monomethyl ether acetate |
Syringe pump | Harvard Apparatus | 703007 | |
Trichlorosilane | Gelest, Inc | SIT8174.0 | Tridecafluoro-1,1,2,2-tetrahydrooctyl. Hazardous. Corrosive to the respiratory tract, reacts violently with water. |
Trypsin Neutralizer Solution | Gibco | R-002-100 |
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