Department of Biomedical Engineering, University of Michigan, Ann Arbor, USA; Biointerfaces Institute, University of Michigan, Ann Arbor, USA.
Biomaterials. 2013 Dec;34(37):9623-31. doi: 10.1016/j.biomaterials.2013.08.046. Epub 2013 Sep 10.
This work describes the use of aqueous two-phase systems to print cell-containing contractile collagen microdroplets. The fully aqueous conditions enable convenient formation of sub-microliter 'microgels' that are much smaller than otherwise possible to fabricate while maintaining high cell viability. The produced microgels contract over several days, mimicking the behavior of macroscale contraction assays, which have been valued as an important biological readout for over three decades. Use of microgels not only reduces reagent consumption and increases throughput of the assay, but also improves transport of molecules into and out of the collagen matrix, thereby enabling efficient and more precise studies of timed stimulation profiles. Utility of the technology is demonstrated by analyzing the effects of TGF-β1 on gel contraction, and we demonstrate that brief 'burst' stimulation profiles in microgels prompt contraction of the matrix, a feature not observed in the conventional macroscale assay. The fully aqueous process also enables the integration of contractile collagen microgels within existing cell culture systems, and we demonstrate proof-of-principle experiments in which a contractile collagen droplet is fabricated in situ on an existing epithelial monolayer. The simplicity, versatility and ability to robustly produce collagen microgels should allow effective translation of this microengineering technology into a variety of research environments.
这项工作描述了使用双水相系统打印含有细胞的收缩性胶原蛋白微滴。完全的水性条件有利于方便地形成亚微米级的“微凝胶”，其尺寸远小于其他方法制造的微凝胶，同时保持高细胞活力。生成的微凝胶在数天内收缩，模拟了宏观尺度收缩测定的行为，这种方法作为一种重要的生物学读出物已经有三十多年的历史。微凝胶的使用不仅减少了试剂的消耗，提高了测定的通量，而且改善了分子进出胶原蛋白基质的传输，从而能够对定时刺激谱进行高效且更精确的研究。该技术的实用性通过分析 TGF-β1 对凝胶收缩的影响得到了证明，我们证明了微凝胶中短暂的“爆发”刺激模式会促使基质收缩，这是在传统的宏观测定中没有观察到的特征。完全的水性过程还能够使收缩性胶原蛋白微凝胶集成到现有的细胞培养系统中，我们演示了初步的实验，其中在现有的上皮细胞单层上原位制造收缩性胶原蛋白液滴。该微工程技术的简单性、多功能性和能够稳健地生产胶原蛋白微凝胶，应该能够使其有效地转化为各种研究环境。
