School of Energy and Power Engineering, Xi'an Jiaotong University, Xi'an 710049, PR China; Bioinspired Engineering and Biomechanics Center (BEBC), Xi'an Jiaotong University, Xi'an 710049, PR China.
Bioinspired Engineering and Biomechanics Center (BEBC), Xi'an Jiaotong University, Xi'an 710049, PR China; State Key Laboratory of Mechanical Structure Strength and Vibration, School of Aerospace, Xi'an Jiaotong University, Xi'an 710049, PR China.
J Mech Behav Biomed Mater. 2018 Jun;82:383-393. doi: 10.1016/j.jmbbm.2018.03.026. Epub 2018 Mar 22.
Cell aggregates represent the main format of cells existing in vivo and have been widely used as tissue and disease models in vitro. Nevertheless, the preservation of cell aggregates while maintaining their functionalities for off-the-shelf applications is still challenging. Among various preservation methods, droplet-based vitrification exhibits superior advantages for the cryopreservation of cell aggregates; however, the physical mechanisms underlying droplet-based vitrification of cell aggregate using this method remain elusive. To address this issue, we proposed a voronoi model to construct two-dimensional geometric morphologies of cell aggregates and established a coupled physical model to describe the diffusion, heat transfer and crystallization processes during vitrification. Based on these models, we performed a numerical study on the variation and distribution of cryoprotectant (CPA) concentration, temperature and crystallization in cell aggregates during droplet-based vitrification. The results show that although cell membrane is not an obvious barrier in heat transfer, it affects the diffusion of CPA remarkably as a biologic film and thus the following crystallization in cell aggregates. The effective protection of CPA during vitrification occurs during the initial stage of CPA diffusion, thus a longer CPA loading time does not necessarily lead to significant decrease in crystallization, but rather may induce more toxicity to cells.
细胞聚集体代表了体内存在的细胞的主要形式，已被广泛用作体外组织和疾病模型。然而，在保持细胞聚集体的功能的同时，将其保存以供即用仍然具有挑战性。在各种保存方法中，基于液滴的玻璃化在细胞聚集体的冷冻保存方面表现出优异的优势；然而，使用这种方法进行基于液滴的细胞聚集体玻璃化的物理机制仍然难以捉摸。为了解决这个问题，我们提出了 Voronoi 模型来构建细胞聚集体的二维几何形态，并建立了一个耦合物理模型来描述玻璃化过程中的扩散、传热和结晶过程。基于这些模型，我们对基于液滴的玻璃化过程中细胞聚集体中细胞保护剂 (CPA) 浓度、温度和结晶的变化和分布进行了数值研究。结果表明，尽管细胞膜在传热中不是一个明显的障碍，但作为生物膜，它会显著影响 CPA 的扩散，从而影响细胞聚集体中的后续结晶。玻璃化过程中，CPA 的有效保护发生在 CPA 扩散的初始阶段，因此较长的 CPA 加载时间不一定会导致结晶显著减少，反而可能会对细胞产生更大的毒性。
