Institute of Macromolecular Chemistry, AS CR , Heyrovsky Sq. 2, Prague, Prague 6, 162 06, Czech Republic.
Biomacromolecules. 2013 Nov 11;14(11):4061-70. doi: 10.1021/bm401186z. Epub 2013 Oct 25.
We report kinetic studies of therapeutically highly potent polymer-drug conjugates consisting of amphiphilic N-(2-hydroxypropyl) methacrylamide (HPMA)-based copolymers bearing the anticancer drug doxorubicin (Dox). Highly hydrophobic cholesterol moieties as well as the drug were attached to the polymer backbone by a pH-sensitive hydrazone bond. Moreover, the structure of the spacer between the polymer carrier and the cholesterol moiety differed in order to influence the release rate of the hydrophobic moiety, and thus the disintegration of the high-molecular-weight micellar nanoparticle structure. We performed time-dependent SAXS/SANS measurements after changing pH from a typical blood value (pH 7.2) to that of tumor cells (pH 5.0) to characterize the drug release and changes in particle size and shape. Nanoparticles composed of the conjugates containing Dox were generally larger than the drug-free ones. For most conjugates, nanoparticle growth or decay was observed in the time range of several hours. It was established that the growth/decay rate and the steady-state size of nanoparticles depend on the spacer structure. From analytical fitting, we conclude that the most probable structure of the nanoparticles was a core-shell or a core with attached Gaussian chains. We concluded that the spacer structure determined the fate of a cholesterol derivative after the pH jump. Fitting results for 5α-cholestan-3-onecholestan-3-one and cholesteryl-4-oxopentanoate (Lev-chol) implied that cholesterol moieties continuously escape from the core of the nanoparticle core and concentrate in the hydrophilic shell. In contrast, cholest-4-en-3-one spacer prevent cholesterol escaping. Dox moiety release was only observed after a change in pH. Such findings justify the model proposed in our previous paper. Lastly, the cholesteryl 4-(2-oxopropyl)benzoate (Opb-Chol) was a different case where after the release of hydrophobic Opb-Chol moieties, the core becomes more compact. The physicochemical mechanisms responsible for the scenarios of the different spacers are discussed.
我们报告了由亲水性 N-(2-羟丙基)甲基丙烯酰胺（HPMA）基共聚物组成的治疗上非常有效的聚合物-药物缀合物的动力学研究，这些共聚物带有抗癌药物阿霉素（Dox）。高度疏水性胆固醇部分以及药物通过 pH 敏感的腙键连接到聚合物主链上。此外，为了影响疏水性部分的释放速率，从而影响高分子量胶束纳米颗粒结构的崩解，聚合物载体和胆固醇部分之间的间隔物的结构也有所不同。我们在将 pH 从典型的血液值（pH7.2）改变为肿瘤细胞的 pH 值（pH5.0）后进行了时变 SAXS/SANS 测量，以表征药物释放以及颗粒尺寸和形状的变化。含有 Dox 的缀合物组成的纳米颗粒通常比无药物的纳米颗粒大。对于大多数缀合物，在数小时的时间范围内观察到纳米颗粒的生长或衰减。结果表明，纳米颗粒的生长/衰减速率和稳态尺寸取决于间隔物结构。通过分析拟合，我们得出结论，纳米颗粒最可能的结构是核壳或带有附着高斯链的核。我们得出结论，间隔物结构决定了胆固醇衍生物在 pH 跃变后的命运。对于 5α-胆甾烷-3-酮、胆甾烷-3-酮和胆甾基-4-氧戊酸酯（Lev-chol）的拟合结果表明，胆固醇部分不断从纳米颗粒核的核心中逸出，并集中在亲水性壳中。相比之下，胆甾-4-烯-3-酮间隔物阻止胆固醇逸出。只有在 pH 发生变化后才观察到 Dox 部分的释放。这些发现证明了我们之前论文中提出的模型是合理的。最后，胆甾基 4-（2-氧代丙基）苯甲酸酯（Opb-Chol）是一个不同的情况，在疏水性 Opb-Chol 部分释放后，核心变得更加紧凑。讨论了负责不同间隔物情况的物理化学机制。
