Multi-L-arginyl-poly-L-aspartate (MAPA), also known as cyanophycin, containing a backbone of polyaspartate with arginine and lysine as side chains, was prepared with recombinant Escherichia coli. The insoluble part (iMAPA) was conjugated with polyethylene glycol (PEG) at two different levels, high (iMAPA(PEG)h) and low (iMAPA(PEG)l). Both levels of conjugation exhibited UCST (upper critical solution temperature)-type responses in the pH range of 3–10 at a concentration of 2 mg/mL. The cloud-point temperature of each conjugate also showed a positive correlation with concentration in PBS, falling between 20 to 58 °C at a concentration from 0.1 to 3 mg/mL. Hysteresis was observed to follow approximate paths under the same condition during repeated heating and cooling. Notably, the reversible formation of core–shell vesicles appeared at room temperature in PBS with a size of around 25 to 60 nm, as measured by DLS and observed under TEM. The reversibility was further employed to encapsulate doxorubicin (Dox) at different weight ratios of Dox to iMAPA(PEG)h. An encapsulation efficiency could reach as high as 70% with an equivalent loading capacity of 1.5 mg Dox/mg iMAPA(PEG)h. The Dox-loaded vesicles stayed stable at 4 °C for up to 4 weeks, with a minimal leakage below 2% and a slightly dilated morphology. Temperature-triggered release of Dox from the vesicles could be achieved by a step change of 5 °C successively from 37 to 62 °C in an effort to induce an initial 10% release at 37 °C gradually to complete release at 62 °C.

中文翻译：

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多元1-精氨酰基-聚-1-天冬氨酸与聚乙二醇共轭制备的UCST反应可逆自组装纳米囊泡

用重组大肠杆菌制备了含有聚天冬氨酸骨架和精氨酸和赖氨酸作为侧链的多-L-精氨酸-聚-L-天冬氨酸（MAPA），也称为蓝霉素。。不溶部分（iMAPA）以高（iMAPA（PEG）h）和低（iMAPA（PEG）l）两种不同水平与聚乙二醇（PEG）缀合。在2-10 mg / mL的pH范围内，两种水平的结合都表现出UCST（临界溶液温度上限）类型的响应。每种缀合物的浊点温度也与PBS中的浓度呈正相关，在0.1至3 mg / mL的浓度范围内介于20至58°C之间。在相同的条件下，反复进行加热和冷却时，磁滞遵循近似路径。值得注意的是，室温下在PBS中可逆形成核-壳囊泡的形成，其大小约为25至60 nm（通过DLS测量并在TEM下观察到）。可逆性还用于以不同的Dox与iMAPA（PEG）h重量比封装阿霉素（Dox）。当等效负载量为1.5 mg Dox / mg iMAPA（PEG）h时，封装效率可高达70％。载有Dox的囊泡在4°C保持稳定长达4周，最小渗漏低于2％，形态略微扩张。通过从37°C到62°C连续5°C的逐步变化，可以实现Dox从囊泡的温度触发释放，以尝试在37°C时逐渐引起最初的10％释放，直至在62°C时完全释放。低于2％的渗漏最小，形态略有扩张。通过从37°C到62°C连续5°C的逐步变化，可以实现Dox从囊泡的温度触发释放，以尝试在37°C时逐渐引起最初的10％释放，直至在62°C时完全释放。低于2％的渗漏最小，形态略微扩张。通过从37°C到62°C连续5°C的逐步变化，可以实现Dox从囊泡的温度触发释放，以尝试在37°C时逐渐引起最初的10％释放，直至在62°C时完全释放。