Department of Biomedical Engineering, Tufts University, Medford, MA 02155, USA.
Department of Biomedical Engineering, Tufts University, Medford, MA 02155, USA.
Acta Biomater. 2019 Sep 1;95:3-31. doi: 10.1016/j.actbio.2018.11.040. Epub 2018 Nov 24.
Unlike unicellular organisms and plant cells surrounded with a cell wall, naked plasma membranes of mammalian cells make them more susceptible to environmental stresses encountered during in vitro biofabrication and in vivo cell therapy applications. Recent advances in micro- and nanoencapsulation of single mammalian cells provide an effective strategy to isolate cells from their surroundings and protect them against harsh environmental conditions. Microemulsification and droplet-based microfluidics have enabled researchers to encapsulate single cells within a variety of microscale hydrogel materials with a range of biochemical and mechanical properties and functionalities including enhanced cell-matrix interactions or on-demand degradation. In addition to microcapsules, nanocoatings of various organic and inorganic substances on mammalian cells have allowed for the formation of protective shells. A wide range of synthetic and natural polymers, minerals and supramolecular metal-organic complexes have been deposited as nanolayers on the cells via electrostatic interactions, receptor-ligand binding, non-specific interactions, and in situ polymerization/crosslinking. Here, current strategies in encapsulation of single mammalian cells along with challenges and advances are reviewed. Protection of encapsulated stem cells, fibroblasts, red and white blood cells and cancer cells against harsh in vitro and in vivo conditions including anoikis, UV radiation, physical forces, proteolytic enzymes and immune clearance are discussed. STATEMENT OF SIGNIFICANCE: The mechanical fragility of the plasma membrane and susceptibility to extracellular biochemical factors due to the lack of a physical barrier like a tough cell wall or exoskeleton make mammalian cells extra sensitive to harsh environmental conditions. This sensitively, in turn, limits the ex vivo storage, handling and manipulation of mammalian cells, as well as their in vivo applications. Environmental stresses such as exposure to UV, reactive chemicals and mechanical stress during biofabrication processes like 3D bioprinting can often compromise cell viability and function. Micro- and nanoencapsulation of single mammalian cells in protective shells have emerged as promising approaches to isolate cells from their surroundings and enhance resistance against perturbations in conditions during regenerative medicine and tissue engineering applications. In this review, the current state of art of single cell encapsulation strategies and the challenges associated with these technologies are discussed in detail. This is followed by the review of the protection provided by cell armor against a range of harsh in vitro and in vivo conditions.
与具有细胞壁的单细胞生物和植物细胞不同，哺乳动物细胞的裸露质膜使它们在体外生物制造和体内细胞治疗应用中更容易受到环境压力的影响。最近在单细胞的微纳封装方面的进展为将细胞与其周围环境隔离并保护它们免受恶劣环境条件的影响提供了一种有效的策略。微乳液法和基于液滴的微流控技术使研究人员能够将单个细胞封装在各种具有不同生化和机械特性和功能的微尺度水凝胶材料中，包括增强细胞-基质相互作用或按需降解。除了微胶囊之外，各种有机和无机物质在哺乳动物细胞上的纳米涂层也允许形成保护性外壳。通过静电相互作用、受体-配体结合、非特异性相互作用和原位聚合/交联，广泛的合成和天然聚合物、矿物质和超分子金属有机配合物已作为纳米层沉积在细胞上。在这里，我们回顾了单细胞哺乳动物细胞的封装策略以及所面临的挑战和进展。讨论了对恶劣的体外和体内条件（包括失巢凋亡、UV 辐射、物理力、蛋白水解酶和免疫清除）的保护，这些条件包括对封装的干细胞、成纤维细胞、红白细胞和癌细胞的保护。意义陈述：由于缺乏物理屏障（如坚韧的细胞壁或外骨骼），质膜的机械脆弱性以及对细胞外生化因子的敏感性，使哺乳动物细胞对恶劣的环境条件格外敏感。这种敏感性反过来又限制了哺乳动物细胞的体外储存、处理和操作，以及它们的体内应用。生物制造过程（如 3D 生物打印）中暴露于 UV、反应性化学物质和机械应力等环境压力常常会损害细胞活力和功能。单细胞哺乳动物细胞在保护性外壳中的微纳封装已成为一种有前途的方法，可以将细胞与其周围环境隔离，并增强其在再生医学和组织工程应用中对条件变化的抵抗力。在这篇综述中，详细讨论了单细胞封装策略的当前技术状态以及与这些技术相关的挑战。接下来，我们回顾了细胞装甲提供的针对一系列恶劣的体外和体内条件的保护。
