Convergence R&D Laboratory, LG Electronics, Seoul 137-130, Korea.
IEEE Trans Biomed Eng. 2013 Feb;60(2):569-75. doi: 10.1109/TBME.2012.2230444. Epub 2012 Nov 29.
The viscoelastic properties of the zona pellucida (ZP), which is the extracellular coat surrounding an oocyte/embryo, are evaluated in this study. Previous studies demonstrate that ZP mechanical properties change during oocyte maturation, fertilization, and early embryo development, but linear pure elastic models currently being used do not satisfy the time-dependent mechanical behavior of the ZP. In this paper, nonlinear viscoelastic characterization was performed using the Hunt-Crossley model and the newly developed vision-based nanoforce estimation method. The results show that viscoelasticity is a physical property of the ZP that exhibits hysteresis. The stiffness and viscosity parameters simultaneously increase following fertilization, causing the stiffness and viscosity of the embryo ZP (ten samples) to be 2.57-fold and 4.44-fold greater, respectively, than that of the oocyte ZP (eleven samples). This behavior well describes the noncovalently cross-linked filamentous structure of the ZP, supporting zona hardening during fertilization as a mechanically relevant event.
本研究评估了卵母细胞/胚胎周围的细胞外囊——透明带的黏弹性特性。先前的研究表明，透明带的机械性能在卵母细胞成熟、受精和早期胚胎发育过程中发生变化，但目前使用的线性纯弹性模型不能满足透明带的时变力学行为。本文使用亨特-克罗斯利模型和新开发的基于视觉的纳米力估计方法进行了非线性黏弹性表征。结果表明，黏弹性是透明带的一种物理特性，表现出滞后现象。受精后，黏弹性和刚性参数同时增加，导致胚胎透明带（十个样本）的刚性和黏性分别比卵母细胞透明带（十一个样本）大 2.57 倍和 4.44 倍。这种行为很好地描述了透明带中无共价交联的丝状结构，支持受精过程中透明带变硬是一个与力学相关的事件。
