A generalizable approach for improving the stability of polylactide-based (PLA-based) micelles for encapsulating nanoparticles (NPs) is demonstrated, using stereocomplexation between a pair of poly (ethylene glycol)-b-poly(d-lactide)/poly(ethylene glycol)-b-poly(l-lactide) block copolymer blends. Three different superparamagnetic ferrite-based NPs with distinct nanostructures are first prepared by the high-temperature pyrolysis method, including spherical MnFe₂O₄, cubic MnFe₂O₄, and core–shell MnFe₂O₄@Fe₃O₄. The diameters of these NPs are approximately 7–10 nm as revealed by transmission electron microscopy. These hydrophobic NPs can be encapsulated within self-assembled, stereocomplexed PLA (sc-PLA) micelles. All sc-PLA micelle systems loaded with three different NPs exhibit enhanced stability at elevated temperatures (20–60 °C) and with extended storage time (∼96 h) compared with analogous samples without stereocomplex formation, confirmed by dynamic light scattering measurements. The magnetic NP-loaded micelles with mean diameters of approximately 150 nm show both biocompatibility and superparamagnetic property. Under a 1.5 T magnetic field, cubic MnFe₂O₄ (c-MnFe₂O₄)-loaded micelles exhibit an excellent negative contrast enhancement of MR signals (373 mM^–1·s^–1), while core–shell MnFe₂O₄@Fe₃O₄-loaded micelles show a slightly lower signal for MR imaging (275 mM^–1·s^–1). These results suggest the potential of using sc-PLA-based polymer micelles as universal carriers for magnetic resonance imaging contrast agents with improved stability for different applications such as cancer diagnosis.

中文翻译：

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分子立体复杂化，以增强包裹在胶束中的纳米粒子的磁共振成像稳定性。

使用一对聚（乙二醇）-b-聚（d-丙交酯）/聚（乙烯）之间的立体络合物，证明了一种用于封装纳米颗粒（NPs）的基于聚丙交酯（基于PLA）的胶束稳定性的通用方法。二醇）-b-聚（1-丙交酯）嵌段共聚物的混合物。首先通过高温热解方法制备了三种不同的具有不同纳米结构的超顺磁性铁氧体纳米颗粒，包括球形MnFe ₂ O ₄，立方MnFe ₂ O ₄和核壳型MnFe ₂ O ₄ @Fe ₃ O _4。。透射电子显微镜显示这些NP的直径约为7-10 nm。可以将这些疏水性NP封装在自组装的立体复合PLA（sc-PLA）胶束中。与没有立体复合物形成的类似样品相比，所有装有三种不同NP的sc-PLA胶束系统在高温（20–60°C）和延长的存储时间（〜96 h）下均表现出增强的稳定性，这通过动态光散射测量得到了证实。平均直径约为150 nm的磁性NP胶束显示出生物相容性和超顺磁性。在1.5 T磁场下，立方MnFe ₂ O ₄（c-MnFe ₂ O ₄）胶束表现出出色的MR信号负对比度增强（373 mM ^–1 ·s ^–1），而核壳MnFe ₂ O ₄ @Fe ₃ O ₄胶束表现出稍低的MR成像信号（275 mM ^–1 ·s ^–1）。这些结果表明，使用基于sc-PLA的聚合物胶束作为磁共振造影剂的通用载体具有提高稳定性的潜力，可用于不同的应用程序，例如癌症诊断。