质膜挠曲电效应及外毛细胞电动性机理研究

It has been experimentally confirmed that outer hair cells (OHC) in the mammalian cochlea are essential to the remarkable sensitivity of hearing. OHCs electromotility is mainly based on the changes of plasma membrane microstructures, plasma membrane surface morphology and plasma membrane curvature with electric stimulation, namely the flexoelectric effect. In this proposal, combining the prestins, the head groups and charges in plasma membrane, we will develop a coupling model including the time-dependent Ginzburg-Landau(TDGL) phase field equations and the Cahn-Hilliard (C-H) diffusion equations to describe evolution of the membrane microstructure. Based on the phase field model, the distributions of membrane charges, electric potential and polarization will be predicted with the various electrical stimulations. Further, the flexoelectric coefficient of membrane will be obtained. Considering the three lateral layers of the cells (plasma membrane, cortical lattice and subsurface cisterna), the unified governing equations of the composite structure will be established using the energy variational principle. The relationship between the spontaneous curvature, flexoelectric effect and axial equivalent piezoelectric coefficient will be explored. Combined with the cell body electrical properties, the electric potential distribution along the longitudinal axis of the cell will be determined. With the various electric boundary conditions, the deformations, dynamics, frequency-dependent power efficiency and electric-mechanical energy conversion mechanism of OHCs will be investigated. The objective of this proposal is to elucidate the mechanism of OHCs electromotility through micro to macro fields and further to provide an effective model for future research of hearing.

实验证实了耳蜗外毛细胞的电动性与耳蜗放大功能的相关性，而外毛细胞的电动性主要基于质膜微结构、质膜表面褶皱形貌和质膜曲率随外电刺激的改变，即挠曲电效应。本项目拟结合膜内动蛋白、官能基团和电荷分布建立描述质膜微结构的时间相关Ginzburg-Landau（TDGL）相场方程和Cahn-Hilliard（C-H）扩散方程。将采用耦合相场模型预测外电刺激对膜内电荷、电势和极化强度分布的影响，进一步获得质膜挠曲电系数。考虑细胞外侧三层结构（质膜、皮层网格和膜下间池），将通过能量变分原理建立复合结构的统一控制方程，探讨质膜的自发曲率、挠曲电效应与胞体轴向等效压电系数的相互关系。结合细胞体电学性能，将讨论胞体纵轴向电势分布，研究外毛细胞的变形、动力学特性和电能机械能转换机制。目的在于阐明外毛细胞电动性的微观和宏观机理，提出一套新的生物力学研究方法，为耳蜗听力的进一步研究提供有效的科学模型。

考虑挠曲电效应和应变梯度效应的单层和多层纳米压电传感器、致动器和俘能器系统，构建了微纳智能系统的的静力学和动力学多场耦合控制方程和相应的力电耦合边界条件，深入研究了机械加载、电学加载和环境振动激励对智能系统的弯曲变形、电学输出和功率输出响应的影响，阐明了挠曲电和压电效应对输出响应的作用从微米尺度逐渐过渡到纳米尺度的变化过程，揭示了物理参数、尺寸效应和外加负载等对智能结构静力学和动力学行为的作用机理和影响规律。进一步建立了描述液晶材料内分子极化取向和局部密度的耦合相场方程，并建立了考虑挠曲电效应的外毛细胞轴向振动与动态电学控制模型，研究了材料参数、环境流体粘度、机械/电学边界条件和细胞尺寸等对细胞变形和电/机械能转换的影响。阐明了外毛细胞电动性的微观和宏观机理。本项目所研究的是微纳智能系统和仿生系统中关键性问题，这些工作能促进力学与材料、生物和工程控制等学科的进一步交叉与融合，推动新型学科领域的发展，还对以挠曲电效应为新热点的微纳智能系统的发展和应用起到推动作用。