研究最前線 No.61

上田 正人 教授


Titanium Oxide Research



Fabrication of Cell Sheets and Development of a Regeneration Technique for Coral Reefs

Pursuing potentials in multiple areas such as regenerative medicine and the global environment


上田 正人 教授

Faculty of Chemistry, Materials, and Bioengineering

Professor Masato Ueda


Earth, society, and economy? The Laboratory of Environmental Materials researches on environmentally friendly materials. Masato Ueda, a professor of the Faculty of Chemistry, Materials, and Bioengineering, has carried out researches on the applications of titanium oxide in various areas. With his experience, he is currently looking for the possible applications of titanium oxide in several areas, such as the development of cell culture vessels and the regeneration of coral reefs.








Application of Chemical Properties That Respond to Ultraviolet Rays

I heard you are focusing on titanium oxide. What type of research is it?

As a photocatalyst, titanium oxide is generally used for both sterilization and deodorization, as well as a material for solar cells. In contrast, I try to use the characteristic properties in the developments of cell culture vessels and regeneration techniques for coral reefs.

First, please explain the development of the cell culture vessels.

Recently, the usage of cell sheets in regenerative medicine has become a popular research topic. They are thin films cultured from human cells, which are attached to affected areas to regenerate organs. To advance this medical treatment, there is a requirement to develop techniques to both fabricate cell sheets and to successfully detach the cultured cells from the vessels without any damage. The state-of-the-art method is to seed cells on a polymer-coated dish, which are then cultured into a sheet. By simply decreasing the temperature, it is possible to detach cell sheet from the culture vessel without damaging the cell-to-cell bonds. With the advent of this technique, the cell sheet engineering has advanced to the clinical stage. Recently, I came up with an idea of developing a new method utilizing the characteristic properties of titanium oxides respond to ultraviolet rays.
 Since cells are living organisms, they can become damaged or cancerous when exposed to ultraviolet rays. On the other hand, titanium oxide is known to absorb ultraviolet rays. Therefore, I fabricated various structures that could protect cells from the ultraviolet element. Consequently, the cell culture vessel converged to a simple structure with a titanium oxide thin film on a glass substrate.
 When the cell culture vessel is illuminated from the backside, the titanium oxide film absorbs the ultraviolet rays. The photo-response at the exposed area on the surface prevents cell adhesion, whereas cells show excellent adhesion at the unexposed region. By adjusting the film thickness, the cells could be perfectly protected from UV rays. Furthermore, if cells are additionally seeded to the vessel, they preferentially adhere to the blank region. Thus, it would be possible to have several types of cells coexisting on a sheet. What one can do with this is to draw with light using cells as the materials.

What do you mean by "draw with light"?

We try to control the adhered position of cells in the same manner as pictures displayed on a tablet. The present titanium oxide film might respond to the blue light with a relatively short wavelength which is emitted by the tablet devices.
 For example, drawing images with light allows blood vessels to be easily embedded in the skin cell sheet. One can only draw cell sheet one layer at a time. However, if the sheets are prepared on multiple tablets, and then are stacked together; it can fabricate 3D structures such as organs. One has to stack up several cell sheets but it is not just a pie-in-the-sky theory. This is a 3D printer based on a new principle.

  • 日本でもここでしか測定できないと、鉄鋼メーカーなどからの委託も多い、環境材料研究室の電気抵抗率測定装置

    An ultra-precision measurement system of electrical resistivity in the Laboratory of Environmental Materials. Many measurement requests from steel manufacturers and others due to its unrivaled performance

  • 上田 正人 教授

The cells don't adhere to the light-exposed areas, whereas preferentially adhere to the shaded ones.








Implanting to Corals?

Can you tell us about your research on encouraging techniques for coral reefs regeneration?

This study is a collaborative project with Professor Tomoyuki Takahashi of the Faculty of Societal Safety Sciences and Professor Hiroaki Tsuruta of the Faculty of Environmental and Urban Engineering. Professor Takahashi launched the project on encouraging coral reef restoration.
 A Ti electrode is placed on the mortar scaffold on which the coral will be adhered to. The piezoelectric device, which generates electricity by fluctuation in tidal current, was developed by Professor Takahashi, is connected to the Ti electrode. The coral fragment is then put on it. Now we currently observe the recovery process at Kushimoto in Wakayama and Yoronjima in Kagoshima. Note that Ti is the most environmentally friendly metal with excellent biocompatibility.
 In the present study, the Ti electrode is coated with titanium oxide. Some organisms called polyps exist on the surface of corals. Polyps have osteoblasts that form the skeletons. Humans have also osteoblasts for bone, whose mechanism is similar to that of the polyps in the corals. Titanium oxide has a high affinity for living organisms. When the surfaces of implants such as artificial joints are coated with titanium oxide, bones form more quickly, and they naturally bond to living bones. Since corals exhibit a formation mechanism of skeleton similar to that of human living bone, corals may adhere very well to titanium oxide. This was my belief, which motivated this research. As expected, coral cells and titanium oxide are extremely compatible. Computerized tomography (CT) scans revealed that the coral skeleton is firmly attached to Ti.

So, you do the undersea work yourself?

I got a diving certification just because of this project. Volunteer divers often help us, but we basically install the samples and related foundations ourselves. As an example, we did physical works in the sea such as hammering of piles. Some of samples were washed away by strong tide under inclement weather. In addition, some of corals cannot sufficiently grow due to an unfavorable environment. However, we patiently install and observe samples and continue to perform trial and error.

What is the future of this research?

The traditional mainstream method of coral reef regeneration is the fragment transplantation where a coral is broken into fragments and then planted. I hope our method will enable more efficient regeneration of coral reefs. We have succeeded in isolating polyps from the fragments of corals, and now we can easily obtain hundreds of polyps by a single operation. I think this is a great achievement. Once these polyps are seeded on titanium oxide, they adhere on it in about half a day; thus, continuous mass production of corals would be possible.

  • 人工股関節の模型

    An artifi cial hip joint

Living bones and skeletons of corals exhibit very similar formation mechanism. Titanium oxide promotes the bone formation on the surface. When a coral fragment is attached to a titanium rod coated with titanium oxide, a soft tissue called polyp covers it quickly.




New Possibilities Through a Different Point of View

What is the true pleasure in your research?

I think it is the discovery of novel areas of application of titanium oxide by having different points of view. When I started to the research on corals, I never thought of using titanium oxide.
 When I was a student, I majored in metallic materials. Up to now, however, I have been involved in a wide range of research, including regenerative medicine, aerospace materials, photocatalysts, and solar cells. I was forcibly involved in certain research projects, but the breadth of knowledge acquired spurred me to my current research. For example, my experience in improving quantum efficiency of solar cells has been useful in the research on the development of cell culture vessel that enables 2D patterning of cells. I am an active American football player in the X League now. Even this experience has been useful in my research work. I hope to continue exploring environmentally friendly materials without being constrained by research trends and preconceptions.


At Professor Ueda's private laboratory. There is his gym equipment.