Dainton Building, Department of Chemistry, The University of Sheffield , Brook Hill, Sheffield, South Yorkshire S3 7HF, United Kingdom.
J Am Chem Soc. 2017 Jun 7;139(22):7616-7623. doi: 10.1021/jacs.7b02642. Epub 2017 May 23.
Dynamic covalent chemistry is exploited to drive morphological order-order transitions to achieve the controlled release of a model payload (e.g., silica nanoparticles) encapsulated within block copolymer vesicles. More specifically, poly(glycerol monomethacrylate)-poly(2-hydroxypropyl methacrylate) (PGMA-PHPMA) diblock copolymer vesicles were prepared via aqueous polymerization-induced self-assembly in either the presence or absence of silica nanoparticles. Addition of 3-aminophenylboronic acid (APBA) to such vesicles results in specific binding of this reagent to some of the pendent cis-diol groups on the hydrophilic PGMA chains to form phenylboronate ester bonds in mildly alkaline aqueous solution (pH ∼ 10). This leads to a subtle increase in the effective volume fraction of this stabilizer block, which in turn causes a reduction in the packing parameter and hence induces a vesicle-to-worm (or vesicle-to-sphere) morphological transition. The evolution in copolymer morphology (and the associated sol-gel transitions) was monitored using dynamic light scattering, transmission electron microscopy, oscillatory rheology, and small-angle X-ray scattering. In contrast to the literature, in situ release of encapsulated silica nanoparticles is achieved via vesicle dissociation at room temperature; moreover, the rate of release can be fine-tuned by varying the solution pH and/or the APBA concentration. Furthermore, this strategy also works (i) for relatively thick-walled vesicles that do not normally exhibit stimulus-responsive behavior and (ii) in the presence of added salt. This novel molecular recognition strategy to trigger morphological transitions via dynamic covalent chemistry offers considerable scope for the design of new stimulus-responsive copolymer vesicles (and hydrogels) for targeted delivery and controlled release of cargoes. In particular, the conditions used in this new approach are relevant to liquid laundry formulations, whereby enzymes require protection to prevent their deactivation by bleach.
动态共价化学被利用来驱动形态有序-无序转变，以实现模型负载（例如，硅纳米粒子）的控制释放，这些负载被包裹在嵌段共聚物囊泡内。更具体地说，通过在水溶液中聚合诱导自组装，制备了聚（甘油单甲基丙烯酸酯）-聚（2-羟丙基甲基丙烯酸酯）（PGMA-PHPMA）两亲性嵌段共聚物囊泡，无论是否存在硅纳米粒子。将 3-氨基苯硼酸（APBA）添加到这些囊泡中，会导致该试剂特异性地与亲水性 PGMA 链上的一些顺式二醇基团结合，在温和碱性水溶液（pH∼10）中形成苯硼酸酯键。这会导致该稳定剂嵌段的有效体积分数略有增加，这反过来又会降低堆积参数，从而诱导囊泡到蠕虫（或囊泡到球体）形态转变。使用动态光散射、透射电子显微镜、振荡流变学和小角 X 射线散射监测共聚物形态的演变（以及相关的溶胶-凝胶转变）。与文献相比，通过室温下囊泡的解离实现了包裹的硅纳米粒子的原位释放；此外，通过改变溶液 pH 值和/或 APBA 浓度可以精细调节释放速率。此外，这种策略还适用于（i）通常不表现出刺激响应行为的相对厚壁囊泡，以及（ii）在添加盐的情况下。通过动态共价化学触发形态转变的这种新型分子识别策略为设计新的刺激响应共聚物囊泡（和水凝胶）提供了广阔的空间，用于靶向输送和负载物的控制释放。特别是，这种新方法中使用的条件与液体洗衣配方相关，其中酶需要保护以防止其被漂白剂失活。
