Cook Alexander B, Novosedlik Sebastian, van Hest Jan C M
Bio-Organic Chemistry, Institute for Complex Molecular Systems, Eindhoven University of Technology, Helix, P.O. Box 513, 5600 MB Eindhoven, The Netherlands.
Acc Mater Res. 2023 Feb 13;4(3):287-298. doi: 10.1021/accountsmr.2c00239. eCollection 2023 Mar 24.
Cells have evolved to be self-sustaining compartmentalized systems that consist of many thousands of biomolecules and metabolites interacting in complex cycles and reaction networks. Numerous subtle intricacies of these self-assembled structures are still largely unknown. The importance of liquid-liquid phase separation (both membraneless and membrane bound) is, however, recognized as playing an important role in achieving biological function that is controlled in time and space. Reconstituting biochemical reactions has been a success of the last decades, for example, establishment of the minimal set of enzymes and nutrients able to replicate cellular activities like the transcription translation of genes to proteins. Further than this though, artificial cell research has the aim of combining synthetic materials and nonliving macromolecules into ordered assemblies with the ability to carry out more complex and ambitious cell-like functions. These activities can provide insights into fundamental cell processes in simplified and idealized systems but could also have an applied impact in synthetic biology and biotechnology in the future. To date, strategies for the bottom-up fabrication of micrometer scale life-like artificial cells have included stabilized water-in-oil droplets, giant unilamellar vesicles (GUV's), hydrogels, and complex coacervates. Water-in-oil droplets are a valuable and easy to produce model system for studying cell-like processes; however, the lack of a crowded interior can limit these artificial cells in mimicking life more closely. Similarly membrane stabilized vesicles, such as GUV's, have the additional membrane feature of cells but still lack a macromolecularly crowded cytoplasm. Hydrogel-based artificial cells have a macromolecularly dense interior (although cross-linked) that better mimics cells, in addition to mechanical properties more similar to the viscoelasticity seen in cells but could be seen as being not dynamic in nature and limiting to the diffusion of biomolecules. On the other hand, liquid-liquid phase separated complex coacervates are an ideal platform for artificial cells as they can most accurately mimic the crowded, viscous, highly charged nature of the eukaryotic cytoplasm. Other important key features that researchers in the field target include stabilizing semipermeable membranes, compartmentalization, information transfer/communication, motility, and metabolism/growth. In this Account, we will briefly cover aspects of coacervation theory and then outline key cases of synthetic coacervate materials used as artificial cells (ranging from polypeptides, modified polysaccharides, polyacrylates, and polymethacrylates, and allyl polymers), finishing with envisioned opportunities and potential applications for coacervate artificial cells moving forward.
细胞已进化为自我维持的分隔系统，由数千种生物分子和代谢物组成，它们在复杂的循环和反应网络中相互作用。这些自组装结构的许多细微复杂之处在很大程度上仍不为人知。然而，液-液相分离（包括无膜和有膜的）的重要性被认为在实现受时间和空间控制的生物学功能中发挥着重要作用。在过去几十年里，重构生化反应取得了成功，例如，建立了能够复制细胞活动（如基因转录翻译为蛋白质）的最小酶和营养物质组合。不过，除了这些，人工细胞研究的目标是将合成材料和无生命大分子组合成有序的组装体，使其具有执行更复杂、更宏大的类似细胞功能的能力。这些活动可以在简化和理想化的系统中深入了解基本的细胞过程，但未来也可能对合成生物学和生物技术产生应用影响。迄今为止，自下而上制造微米级类生命人工细胞的策略包括稳定的油包水液滴、巨型单层囊泡（GUV）、水凝胶和复合凝聚层。油包水液滴是研究类细胞过程的一个有价值且易于制备的模型系统；然而，缺乏拥挤的内部环境可能会限制这些人工细胞更紧密地模拟生命。同样，膜稳定的囊泡，如GUV，具有细胞的额外膜特征，但仍然缺乏大分子拥挤的细胞质。基于水凝胶的人工细胞具有大分子致密的内部（尽管是交联的），能更好地模拟细胞，此外其机械性能更类似于细胞中所见的粘弹性，但可能被视为本质上不具动态性，限制了生物分子的扩散。另一方面，液-液相分离的复合凝聚层是人工细胞的理想平台，因为它们能最准确地模拟真核细胞质拥挤、粘稠、高电荷的性质。该领域研究人员关注的其他重要关键特征包括稳定的半透膜、分隔、信息传递/通信、运动性以及代谢/生长。在本综述中，我们将简要介绍凝聚理论的各个方面，然后概述用作人工细胞的合成凝聚层材料的关键案例（范围从多肽、改性多糖、聚丙烯酸酯、聚甲基丙烯酸酯和烯丙基聚合物），最后展望凝聚层人工细胞未来的机遇和潜在应用。
