We made cell fibers and a fluid device for making them in order to apply the synthetic yeasts into the bandage of our project. Cell fiber is the tubular hardware of which the yeast cells are embedded in its central part. This hardware is placed inside of a bandage pad and retains body fluids as a wound dressing. Cell fiber makes it possible to selectively pass through the relatively small molecules needed for wound detection and antibacterial activity, while preventing the yeast penetration. As we could not use the machines in the laboratory which can make cell fibers precisely due to the COVID-19 pandemic, we developed a fluid device that enables us to make cell fibers at home.
In this page, we will focus on the structure of cell fibers and the way to make them. We think cell fibers are so useful that it can be a breakthrough for iGEM projects. For detailed information on how we can apply cell fibers to various tracks of iGEM projects, see the Excellence in Another area page.
Although cells can be applied in many fields to build a better world
By developing a fluid device, we created the cell fiver using only pin vise and acrylic plates. This approach helped us to create them more inexpensively than using a 3D printer described in the previous research on homemade fluid devices.
Cell fibers have a two-layered structure called core shell. The core of cells are covered with a shell made of calcium alginate gel. This tubular structure enables us to treat the cells as a fiber.
We developed a fluid device which helped us to make cell fibers at home. Injecting the materials for the core and shell of cell fiber (Fig. 2 B), the fiber is formed inside of this device.
The fluid device shapes a laminar flow with the cell suspension on the inside and the sodium alginate solution on the outside. When this flow is poured into a calcium chloride solution, an insoluble gel of calcium alginate is formed on the outside, sealing the cells inside.
- acrylic plate (about 2cm square)
- pin vise (0.3, 0.5, 1.2mm)
Make a hole in the side of a 2 cm square acrylic plate with a thickness of about 3mm as shown in Fig 3. First, drill a 0.5 mm hole without penetration, and then drill a 0.3 mm hole through the middle of the hole. Next, drill a 1.2 mm hole from the side, overlapping the 0.5 mm hole.
First, we inserted a syringe with a 0.3-mm-diameter needle into the 0.3-mm hole (inhaled the cell suspension) and a syringe with a 1.2-mm-diameter needle into the 1.2-mm hole (inhaled the sodium alginate solution). At this time, the tip of the 0.3 mm needle was deeper than the lateral hole (Fig. 4). Then we dipped the 0.5-mm hole in the 50mM calcium chloride aqueous solution and pushed the syringe to eject the cell suspension and 1.5% sodium alginate solution. At that time, we adjusted the pushing force so that laminar flow is created and the thickness of the extruded fiber remains constant. After having maked cell fibers, we washed cell fibers with YPD culture medium. After that, the cell fibers were cultured as normal yeasts.
Using the microfluidic device described above, we succeeded in making cell fibers, which our synthetic yeast cells are packed inside the calcium alginate gel (Fig. 6). These fibers are long enough to be used in the bandage. Observing the cell fiber with a stereomicroscope, yeast cells introduced with pCyc-mCherry[BBa_K3804014] plasmids were correctly aligned in the central part of the gel.
With these results, we believe that we can pack the yeasts safely inside of the bandage using cell fibers.
As a next step, we are planning to improve its making process so that we can stabilize the fiber creation. On the first try of our experiment, it was difficult to see the laminar flow without using a loupe, and we observed some places in the fiber with a microscope where yeast didn’t enter the center of the fiber and leaked.
One of the factors of the failures seems to be that the holes were not straight. This might be a limitation of manual work, but if we can mechanize the process, including the constant pressure of the syringe, we can stably make better cell fibers.