Xu Dasen, Zhang Chongyu, Peng Ruining, Zhang Ru, Chen Haoyu, Li Yulong, Yang Hui
Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang, China.
School of Life Science, Northwestern Polytechnical University, Xi'an, Shaanxi, China.
Front Bioeng Biotechnol. 2025 Jun 10;13:1574853. doi: 10.3389/fbioe.2025.1574853. eCollection 2025.
Single living cells exhibit both active biological functions and material-like mechanical behaviors. While extensive research has focused on static or quasi-static loading, the purely mechanical properties under high-rate impact remain underexplored. Investigating cell responses to dynamic loading can isolate rapid deformation characteristics, potentially clarifying how life activities modulate mechanical behavior.
We developed a custom dynamic loading system to expose single adherent macrophage cells to transient compression-shear stresses in a controlled fluid environment. A Polymethyl Methacrylate chamber housed the cells, and impact pressures (156.48-3603.85 kPa) were measured in real time using a high-frequency sensor. High-speed imaging (up to 2×10 fps) captured cellular area changes, providing insight into global deformation. In total, 198 valid experiments were performed, and statistical tests confirmed that initial perimeter and area followed normal-like distributions suitable for theoretical analysis.
Cells demonstrated a two-stage expansion under shock loading. At lower pressures, cytoplasmic regions rapidly spread into the focal plane, producing significant increases in projected area. As pressure rose further, deformation rate decreased, reflecting the constraining influence of the nucleus. By analyzing the final-to-initial area ratios across various pressures and initial cell sizes, we derived an incomplete state equation akin to Tait-like or Birch-Murnaghan models, indicating an inflection point of maximum deformation rate.
These findings highlight that fast impact loading effectively minimizes confounding biological processes, revealing intrinsic mechanical responses. The proposed state equation captures cell behavior within milliseconds, offering a path to integrate dynamic results with slower, life-activity-driven adaptations, and laying groundwork for more comprehensive biomechanical models of living cells.
单个活细胞既表现出活跃的生物学功能，又具有类似材料的力学行为。虽然广泛的研究集中在静态或准静态加载上，但高速冲击下的纯力学性能仍未得到充分探索。研究细胞对动态加载的反应可以分离出快速变形特征，有可能阐明生命活动如何调节力学行为。
我们开发了一种定制的动态加载系统，以在可控的流体环境中使单个贴壁巨噬细胞暴露于瞬态压缩剪切应力。一个聚甲基丙烯酸甲酯腔室容纳细胞，并使用高频传感器实时测量冲击压力（156.48 - 3603.85 kPa）。高速成像（高达2×10帧/秒）捕捉细胞面积变化，从而深入了解整体变形情况。总共进行了198次有效实验，统计测试证实初始周长和面积遵循适合理论分析的类似正态分布。
细胞在冲击载荷下呈现出两阶段膨胀。在较低压力下，细胞质区域迅速扩展到焦平面，导致投影面积显著增加。随着压力进一步升高，变形速率降低，这反映了细胞核的约束作用。通过分析不同压力和初始细胞大小下的最终面积与初始面积之比，我们推导出了一个类似于泰特（Tait）或伯奇 - 莫纳汉（Birch - Murnaghan）模型的不完整状态方程，表明存在最大变形速率的拐点。
这些发现突出表明，快速冲击加载有效地最小化了混杂的生物学过程，揭示了内在的力学响应。所提出的状态方程在毫秒内捕捉细胞行为，为将动态结果与较慢的、生命活动驱动的适应性相结合提供了一条途径，并为更全面的活细胞生物力学模型奠定了基础。
