Bos Inge, Timmerman Marga, Sprakel Joris
Physical Chemistry and Soft Matter, Wageningen University & Research, Stippeneng 4, 6708 WE Wageningen, The Netherlands.
Macromolecules. 2021 Jan 12;54(1):398-411. doi: 10.1021/acs.macromol.0c02387. Epub 2020 Dec 24.
Complex coacervate core micelles (C3Ms) are nanoscopic structures formed by charge interactions between oppositely charged macroions and used to encapsulate a wide variety of charged (bio)molecules. In most cases, C3Ms are in a dynamic equilibrium with their surroundings. Understanding the dynamics of molecular exchange reactions is essential as this determines the rate at which their cargo is exposed to the environment. Here, we study the molecular exchange in C3Ms by making use of Förster resonance energy transfer (FRET) and derive an analytical model to relate the experimentally observed increase in FRET efficiency to the underlying macromolecular exchange rates. We show that equilibrated C3Ms have a broad distribution of exchange rates. The overall exchange rate can be strongly increased by increasing the salt concentration. In contrast, changing the unlabeled homopolymer length does not affect the exchange of the labeled homopolymers and an increase in the micelle concentration only affects the FRET increase rate at low micelle concentrations. Together, these results suggest that the exchange of these equilibrated C3Ms occurs mainly by expulsion and insertion, where the rate-limiting step is the breaking of ionic bonds to expel the chains from the core. These are important insights to further improve the encapsulation efficiency of C3Ms.
复合凝聚核心胶束（C3M）是由带相反电荷的大离子之间的电荷相互作用形成的纳米结构，用于封装多种带电（生物）分子。在大多数情况下，C3M与其周围环境处于动态平衡。了解分子交换反应的动力学至关重要，因为这决定了其负载物暴露于环境的速率。在这里，我们利用Förster共振能量转移（FRET）研究C3M中的分子交换，并推导了一个分析模型，将实验观察到的FRET效率增加与潜在的大分子交换速率联系起来。我们表明，平衡的C3M具有广泛的交换速率分布。通过增加盐浓度可以显著提高整体交换速率。相比之下，改变未标记的均聚物长度不会影响标记均聚物的交换，并且胶束浓度的增加仅在低胶束浓度下影响FRET增加速率。总之，这些结果表明，这些平衡的C3M的交换主要通过排出和插入发生，其中限速步骤是打破离子键以将链从核心排出。这些是进一步提高C3M封装效率的重要见解。
