What is Cell Fiber?
In this project, we used cell fiber to incorporate cells into the products. It is a technique that is to confine the cells inside a tube of calcium alginate, which was developed in Takeuchi Lab., the University of Tokyo [1]. As we wrote on the Hardware page, making it is quite easy, as you can make it in your home(of course, you should not use LMO if you are in the Member Country of the Cartagena Agreement) [2]. Because of its usefulness, we thought this technique could be a breakthrough for iGEM, and discussed how it can be used in iGEM. The summary is written on this page.
In iGEM, many projects have difficulties integrating cells into a real device, although they make brilliant synthetic cells. In many cases, cell fibers have many advantages. The most important point of cell fibers is that cells are trapped inside, while smaller molecules such as the substrates and products are transmitted through them. It is useful as a material, too. You can use it as just a fiber, or measure it in length, which is a much easier way to count cells. In addition, cell fiber is used to weave up into cloth. Moreover, it can isolate different types of cells so that they don’t compete with each other and cause one of them to become extinct. Cell fiber will extend the possibilities of iGEM projects.
Fig. 1 The structure of cell fiber
How to Make Cell Fibers
Making cell fibers is not very difficult. There are some ways to make them, and you should choose by the required property, quality, and cost. Here, we show two of them which are used in our project, both of them are cheap and easy.
Fig. 2Structure of single-layered Cell Fiber (left) and Core-Shell Cell Fiber (right).
Single-layered Cell Fiber
Single-layered cell fiber is the simplest form of cell fiber. It only has a limited function of cell fibers. Although it has limited trapping ability and it affects the culturing environment, it is a good way to try cell fibers or operate cells as fiber. All you need to make single-layered cell fiber is to suspend cells in 1.5% and eject it into a calcium chloride aqueous solution with a syringe and needle. (Maybe it is better to use a chloride-added culture medium if you use delicate cells.) You can culture cell fibers in the liquid culture medium.
Core-Shell Cell Fiber
Core-Shell cell fiber is the cell fiber we explained above. In this project, if we say cell fiber, it means this core-shell cell fiber. Making it was relatively complex with the conventional method; however, we developed a more straightforward and cheaper method. To make core-shell cell fiber, you need to make a microfluidic device with an acrylic plate. The making process is only cutting and drilling. The cost to make the device was about 3,000-yen (30 USD). The device can make concentric laminar flows: the inner flow is cell suspension, and the outer one is sodium alginate solution. Ejecting the flows to chloride solution, and the flows become core-shell cell fiber. After washing them with medium and culture in the liquid medium, the cell fiber is completed. See Hardware page for detail.
Fig. 3 Created core-shell cell fiber
Usage in Tracks
We discussed some ways to use cell fibers in some tracks. We show some of them here.
Diagnostics
You can make cells that emit a reporter encapsulated in cell fibers to create a device that is easy to use for diagnosis. For example, by creating cells that react to substances that indicate cancer, encapsulating them in cell fibers, and weaving them into sheets, diagnosis can be made by submerging the cloth or pouring a sample over it, rather than mixing it with a liquid.
Environment
By passing contaminated water through cell fibers as one of the filter materials, the water can be treated continuously. For example, by placing cells that denitrify nitrogen in cell fibers, you can pass sewage through them to reduce the nitrogen content.
Food & Nutrition
Cells in cell fibers can produce nutrients. If you make them secrete, you don’t need to homogenize them, and you don’t need to mix recombined bacteria (or their corpses) with your food. For example, by pouring a solution of raw materials into a reactor with cell fiber, a solution containing vitamin A can be obtained continuously, which can then be used for cooking.
Therapeutics
You can make cells to make what the body needs to make what the body lacks or needs to improve in the body. Cell fibers will prevent the cells from spreading throughout the body. For example, Implanting cell fibers in patients with type 1 diabetes to produce insulin in response to some stimulation.
Try to adapt it to a real project
We then talked about how to adapt cell fibers into a real project. We will show some here.
UTokyo 2021
It is our project. Yeasts are trapped in cell fibers by type. One of them emits defensin to protect injury from infection; the second detects AHL to detect infection; the last senses oxygen to monitor the condition of the injury. Each cell fiber is fixed in dressing material, which covers the wound.
YEAST-AID
Kyoto 2021
It is our partner, iGEM Kyoto’s project. They are trying to reduce flower loss. They also make defensin but not on site. However, cell fibers are useful to use in factories, too. If you incubate cells in cell fibers, the culture medium contains defensin. You do not need to disrupt cells.
FLOWEREVER
Qdai 2020
They tried to make cells that absorb phosphoric acid and store it as polyphosphoric acid. If using cell fibers, they can be used as filter media. Compared to suspending cells in polluted water directly, exchanging of cells is quite easy and can be treated continuously. In addition, the risk of efflux is lower.
Team Qdai 2020
BEAS China 2019
The project of BEAS China, 2019 is idealistic for cell fiber. They made a wonderful system for heavy metal bioremediation, including hardware devices. However, they did not show how to set cells into the device. Cell fibers can be a good solution. They can be used as a filter material in their hardware. In this case, cell fibers are very convenient because they are easy to be replaced with a new one, and they can prevent cells from outflowing.
NEZHA