膜タンパク質が機能する半導体基板上の人工細胞

半導体基板に形成した微小井戸を脂質二分子膜でシールすることで,膜タンパク質が機能する場,すなわち人工細胞を形成する. 膜タンパク質が機能するのに必要なものだけを用いて,化学的に制御された人工細胞環境を構築する. いろいろなタンパク質やその他生体分子が複雑に連携して機能している細胞を,単純化・明確化した系として膜タンパク質本来の機能を計測する. 半導体微細加工技術によりアレイ化することで,高集積化,ハイスループット化が期待できる. 膜タンパク質の機能計測を通して,生体内の情報伝達メカニズムの解明を目指す. 同時に,疾病の早期診断や創薬におけるハイスループットスクリーニング等,健康・医療応用にも貢献する基礎技術の確立を目指す.


Artificial Cell

The Ca2+ ion indicator fluo-4 was confined in the microwells. Then, to analyze the Ca2+ ion transport through the ion channels, a difference was established between the Ca2+ ion concentrations of the microwells and the outer solution by adding CaCl2 to the outer solution until its concentration reached 1 mM. When α-hemolysin was added to the outer solution, it diffused to the suspended lipid bilayer and formed the ion channels. The Ca2+ ions were transported from the outer solution to inside the microwells through the ion channels and the fluorescence intensity of fluo-4 in the microwells increased. The microwell volume was very small (1~100 femtoliters), so a highly sensitive monitor could be realized.

Ref: Biosensors and Bioelectronics 31, 445 (2012).



Artificial Cell

The localization of liquid-ordered (Lo) and liquid-crystalline (Lα) phase domains on a silicon substrate with a microwell array is investigated. Although the phase separation of the Lo and Lα phases on both a giant unilamellar vesicle (GUV) and a supported membrane remains stable for a long time, the lateral diffusion of lipids across each domain boundary occurs quickly. Since the phase separation and domain arrangement are governed by the stiffness and lateral tension of the lipid membrane, the phase separation is rearranged on a micropatterned substrate. Similar phase separation of the Lo and Lα phases is observed at a lipid membrane suspended over a microwell. However, the Lα phase is preferred at a suspended membrane, and saturated lipids and cholesterol are excluded towards the supporting membrane on the periphery. Since the Lo domain area is reduced by anisotropic diffusion through the boundary between the suspended and supported membranes, a very slow reduction rate with a linear functional relation is observed. Finally, a localized Lα phase domain is observed at a membrane suspended over a microwell, which is surrounded by an Lo phase supported membrane.

Ref: Langmuir 33, 13277 (2017).



Previous research topics

半導体ナノ構造の形成制御と構造解析

Si/Ge系を中心として半導体表面における,ナノ構造の形成メカニズムに関する研究を行ってきた. 100 keV程度のH+やHe+イオンをプローブとした中速イオン散乱法(MEIS)や,走査トンネル顕微鏡(STM),原子間力顕微鏡(AFM)等の表面敏感な計測手法を用いて,シリコンとゲルマニウムの相互拡散や表面超構造形成による歪の緩和とナノ構造形成について調べてきた. Si(113)表面上のGe薄膜成長においては,その異方性のため特徴的な表面超構造を形成する事を明らかにした. また,歪の異方的な緩和とGeナノワイヤ形成について,そのメカニズムを明らかにした.


Ge nanowire

We have investigated the strain state in Ge nanowires on Si(113) substrate using MEIS. We found that nanowires have negligibly relaxed compressive strain along their length, but the strain across them is almost totally relaxed. Anisotropic strain relaxation plays a role in determining the width of the nanowires.

Ref: Physical Review B 67, 035319 (2003).



Surface reconstructed structure

Based on STM observations of the epitaxial growth of Ge on Si(113) and first-principles total energy and band calculations, we proposed new reconstruction model for the Ge/Si(113)-2x2 surface. We believe that such unique surface reconstruction resulting in anisotropic surface strain can play a crucial role in deciding the nature of growth on these high-index surfaces.

Ref: Physical Review Letters 88, 266101 (2002).



ウエアラブル電極による生体信号の常時モニタリング

導電性ポリマーと糸や布などの繊維を複合化することで,生体親和性が高くフレキシブルな生体電極が実現できる. このような生体にやさしい電極は,体表面で心電図や脳波のような生体信号を取得する電極に適している. この電極を配置したシャツは,着るだけで心電図等の生体情報を,患者さんに負担を与える事無く常時モニタリングするツールとして期待される.