Poly(lactic acid)-poly(ethylene oxide) (PLA-PEG) nanoparticles: NMR studies of the central solidlike PLA core and the liquid PEG corona
Poly(lactic acid)-poly(ethylene oxide) (PLA-PEG) nanoparticles: NMR studies of the central solidlike PLA core and the liquid PEG corona
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DOI：
10.1021/la011393y
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发表时间：
2002-04-30
期刊：
影响因子：
3.9
通讯作者：
Gellert, PR
中科院分区：
文献类型：
--
作者：
Heald, CR;Stolnik, S;Gellert, PR
用核磁共振法研究了聚乳酸-聚环氧乙烷（PLA-PEG）二嵌段共聚物在d（6）-丙酮和D_2O中的结构。使用改进的界面聚合物沉积-溶剂蒸发技术获得PLA-PEG共聚物的纳米颗粒（Fessi，H.; Devissaguet，J. P.; Puisieux，F.;蒂斯角法国专利2608988，1986）。在D2 O中，PLA嵌段形成中央疏水性核心，而PEG嵌段形成亲水性冠层。在D2O中，通常看不到纳米颗粒的疏水核，而观察到PEG冠。只有在两个区域之间的界面处的PLA甲基质子被观察到，并且这些被视为双二重态结构。对于具有低分子量PLA嵌段长度的纳米颗粒，观察到额外的甲基多重峰信号，表明PLA甲基处于多于一种化学环境中。这对于具有高分子量PLA嵌段长度的纳米颗粒没有观察到，表明在芯界面区域中的结构更均匀。随着温度的升高，后者的核心变得更像液体。PEG冠层的定量校准研究表明，可以看到大部分PEG层，这表明它处于液相中并且在纳米颗粒的表面上。C-13固态NMR光谱研究表明，在PLA-PEG界面处存在中心固体状核和更移动的界面区域，而从T1研究获得的纳米颗粒的弛豫速率表明PEG冠是比界面甲基质子更移动的环境。
NMR studies on a series of poly(lactic acid) - poly(ethylene oxide) (PLA-PEG) diblock copolymers have been carried out in d(6)-acetone and in D2O. Nanoparticles of the PLA-PEG copolymers were obtained using a modified interfacial polymer deposition-solvent evaporation technique (Fessi, H.; Devissaguet, J. P.; Puisieux, F.; Thies, C. French Patent 2 608 988, 1986). In D2O, the PLA block forms a central hydrophobic core, while the PEG block forms an hydrophilic corona layer. In D2O, the hydrophobic core of the nanoparticle is generally not seen, while the PEG corona is observed. Only the PLA methyl protons at the interface between the two regions are observed, and these are seen as a double doublet structure. For nanoparticles with a low molecular weight PLA block length, an additional methyl multiplet signal is seen suggesting that PLA methyl groups are in more than one chemical environment. This is not seen for nanoparticles with a high molecular weight PLA block length indicating more uniform structure in the core interfacial region. As temperature is increased, the core of the latter becomes more liquidlike. Quantitative calibration studies of the PEG corona layer show that most of the PEG layer is seen indicating that it is in the liquid phase and on the surface of the nanoparticle. C-13 solid-state NMR spectroscopy studies indicate the presence of a central solidlike core and a more mobile interfacial region at the PLA-PEG interface, while the relaxation rate of the nanoparticle obtained from T, studies indicates that the PEG corona is a much more mobile environment than the interfacial methyl protons.