Abstract：
Inspired by the unique functionalities of biomolecular membraneless organelles (MLOs) formed via liquid-liquid phase separation (LLPS) of intrinsically disordered proteins (IDPs) and nucleic acids, a great deal of effort has been devoted to devising phase-separated artificial subcellular dynamic compartments. These endeavors aim to unravel the molecular mechanism underlying the formation and intracellular delivery of susceptible macromolecular therapeutics. We report herein pyroglutamic acid (PGA)-based well-defined homopolymers featuring stimuli-tunable reversible self-coacervation ability. The polymer exhibits an upper critical solution temperature (UCST) transition in aqueous solutions and has the propensity to undergo cooling-induced LLPS, producing micrometer-sized liquid droplets. This phase separation phenomenon could be modulated by various factors, including polymer concentration, chain length, solution pH, and types and concentrations of different additives. These micrometer droplets are thermally reversible and encapsulate a wide variety of cargoes, including small hydrophobic fluorescent molecules, hydrophilic anticancer drugs, and fluorophore-labeled macromolecular proteins (bovine serum albumin and lysozyme). The payloads were released by exploiting the thermo/pH-mediated disassembly behavior of the coacervates, preserving the bioactivity of the sensitive therapeutics. This environmentally responsive, simple yet versatile artificial MLO model system will provide insights into the biomolecular nonionic condensates and pave the way for the de novo design of dynamic biomolecule depots.
摘要：
受通过固有无序蛋白质（IDPs）和核酸的液-液相分离（LLPS）形成的生物分子无膜细胞器（MLO）的独特功能的启发，在设计相分离的人工亚细胞动态区室方面投入了大量的努力。这些努力旨在揭示易感大分子治疗剂的形成和细胞内递送的潜在分子机制。我们在此报告了基于焦谷氨酸（PGA）的定义明确的均聚物，其特征在于刺激可调的可逆自凝聚能力。聚合物在水溶液中表现出最高临界溶液温度（UCST）转变，并且具有经历冷却诱导的LLPS的倾向，产生微米大小的液滴。这种相分离现象可以由各种因素调节，包括聚合物浓度，链长,溶液pH值,以及不同添加剂的类型和浓度。这些微米液滴是热可逆的，并封装了各种各样的货物，包括小的疏水荧光分子，亲水性抗癌药物，和荧光团标记的大分子蛋白（牛血清白蛋白和溶菌酶）。通过利用凝聚层的热/pH介导的分解行为来释放有效载荷，保持敏感治疗剂的生物活性。这种环保反应，简单而通用的人工MLO模型系统将提供对生物分子非离子缩合物的见解，并为动态生物分子库的从头设计铺平道路。
