Feedback microrheology in living cells

2018 Fiscal Year Final Research Report

• Project/Area Number: 15H03710
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Biological physics/Chemical physics/Soft matter physics
• Research Institution: Kyushu University
• Principal Investigator: Mizuno Daisuke 九州大学, 理学研究院, 准教授 (30452741)
• Project Period (FY): 2015-04-01 – 2018-03-31
• Keywords: 細胞力学 / マイクロレオロジー / 非平衡統計 / 揺動散逸定理 / 非平衡力学

Outline of Final Research Achievements

Living cells are composed of active materials, in which forces are generated by energy derived from metabolism. Understanding the out-of-equilibrium mechanics is challenging because constituent materials are heterogeneous and their physical properties are strongly affected by the internally generated forces. Here, we have analyzed dynamics inside eukaryotic cells with simultaneous active and passive microrheology using laser interferometry and optical trapping technology. We developed a method to track microscopic probes stably in cells in the presence of vigorous cytoplasmic fluctuations, by employing smooth 3D feedback of a piezoactuated sample stage. We present a theory that adapts the fluctuation-dissipation theorem to out-of-equilibrium systems that are subjected to positional feedback. We discuss the interplay between material properties and non-thermal force fluctuations in the living cells that we quantify through the violations of the FDT.

Free Research Field

ソフトマター・生物物理

Academic Significance and Societal Importance of the Research Achievements

生体中のソフトマタ―は、熱的な揺らぎよりもはるかに大きな力の生成と散逸によって非平衡状態に駆動されている。細胞や生体組織の様々な機能は、生体ソフトマターが力学的に駆動されることでその性質を多彩に変化させる中で発現している。今回、生体ソフトマターの複合体が織りなす非線形・非平衡系の動力学を究明するための有効な手段として、非平衡度と力学特性を同時観測できるActive/Passive MR法を開発した。多重フィードバックにより生体系に特有の巨大な揺らぎに追随し、系に余計な力学的擾乱を与えずにMR観測を行うことで、生き物の非平衡力学挙動の動作原理の一端を知る知見を得ることが出来た。