Cacace David N, Rowland Andrew T, Stapleton Joshua J, Dewey Daniel C, Keating Christine D
Department of Chemistry, and ‡Materials Research Institute, The Pennsylvania State University , University Park, Pennsylvania 16802, United States.
Langmuir. 2015 Oct 20;31(41):11329-38. doi: 10.1021/acs.langmuir.5b02754. Epub 2015 Oct 8.
Mineral deposition within living cells relies on control over the distribution and availability of precursors as well as the location and rates of nucleation and growth. This control is provided in large part by biomolecular chelators, which bind precursors and regulate their availability, and compartmentalization within specialized mineralizing vesicles. Biomimetic mineralization in self-assembled lipid vesicles is an attractive means of studying the mineralization process, but has proven challenging due to vesicle heterogeneity in lamellarity, contents, and size across a population, difficulties encapsulating high and uniform precursor concentrations, and the need to transport reagents across an intact lipid bilayer membrane. Here, we report the use of liposome-stabilized all-aqueous emulsion droplets as simple artificial mineralizing vesicles (AMVs). These biomimetic microreactors allow the entry of precursors while retaining a protein catalyst by equilibrium partitioning between internal and external polymer-rich phases. Small molecule chelators with intermediate binding affinity were employed to control Ca(2+) availability during CaCO3 mineralization, providing protection against liposome aggregation while allowing CaCO3 formation. Mineral deposition was limited to the AMV interior, due to localized production of CO3(2-) by compartmentalized urease. Particle formation was uniform across the entire population of AMVs, with multiple submicrometer amorphous CaCO3 particles produced in each one. The all-aqueous emulsion-based approach to biomimetic giant mineral deposition vesicles introduced here should be adaptable for enzyme-catalyzed synthesis of a wide variety of materials, by varying the metal ion, enzyme, and/or chelator.
活细胞内的矿物质沉积依赖于对前体的分布和可用性以及成核和生长的位置和速率的控制。这种控制在很大程度上由生物分子螯合剂提供，它们结合前体并调节其可用性，以及在专门的矿化囊泡内进行区室化。自组装脂质囊泡中的仿生矿化是研究矿化过程的一种有吸引力的方法，但由于群体中囊泡在层状结构、内容物和大小方面的异质性、封装高且均匀的前体浓度的困难以及将试剂运输穿过完整脂质双层膜的需要，已证明具有挑战性。在这里，我们报告了使用脂质体稳定的全水乳液液滴作为简单的人工矿化囊泡（AMV）。这些仿生微反应器允许前体进入，同时通过内部和外部富含聚合物的相之间的平衡分配保留蛋白质催化剂。在碳酸钙矿化过程中，使用具有中等结合亲和力的小分子螯合剂来控制Ca(2+)的可用性，在允许碳酸钙形成的同时提供防止脂质体聚集的保护。由于通过区室化脲酶局部产生CO3(2-)，矿物质沉积仅限于AMV内部。在整个AMV群体中颗粒形成是均匀的，每个AMV中产生多个亚微米级的无定形碳酸钙颗粒。这里介绍的基于全水乳液的仿生巨型矿化囊泡方法应该可以通过改变金属离子、酶和/或螯合剂来适用于多种材料的酶催化合成。
