Department of Chemistry, Faculty of Science, Mahidol University, Bangkok, Thailand.
Nanotechnology. 2010 Mar 26;21(12):125102. doi: 10.1088/0957-4484/21/12/125102. Epub 2010 Feb 25.
Lipid nanoparticles are a promising alternative to existing carriers in chemical or drug delivery systems. A key challenge is to determine how chemicals are incorporated and distributed inside nanoparticles, which assists in controlling chemical retention and release characteristics. This study reports the chemical and structural investigation of gamma-oryzanol loading inside a model lipid nanoparticle drug delivery system composed of cetyl palmitate as solid lipid and Miglyol 812 as liquid lipid. The lipid nanoparticles were prepared by high pressure homogenization at varying liquid lipid content, in comparison with the gamma-oryzanol free systems. The size of the lipid nanoparticles, as measured by the photon correlation spectroscopy, was found to decrease with increased liquid lipid content from 200 to 160 nm. High-resolution proton nuclear magnetic resonance ((1)H-NMR) measurements of the medium chain triglyceride of the liquid lipid has confirmed successful incorporation of the liquid lipid in the lipid nanoparticles. Differential scanning calorimetric and powder x-ray diffraction measurements provide complementary results to the (1)H-NMR, whereby the crystallinity of the lipid nanoparticles diminishes with an increase in the liquid lipid content. For the distribution of gamma-oryzanol inside the lipid nanoparticles, the (1)H-NMR revealed that the chemical shifts of the liquid lipid in gamma-oryzanol loaded systems were found at rather higher field than those in gamma-oryzanol free systems, suggesting incorporation of gamma-oryzanol in the liquid lipid. In addition, the phase-separated structure was observed by atomic force microscopy for lipid nanoparticles with 0% liquid lipid, but not for lipid nanoparticles with 5 and 10% liquid lipid. Raman spectroscopic and mapping measurements further revealed preferential incorporation of gamma-oryzanol in the liquid part rather than the solid part of in the lipid nanoparticles. Simple models representing the distribution of gamma-oryzanol and lipids (solid and liquid) inside the lipid nanoparticle systems are proposed.
脂质纳米粒是化学或药物传递系统中现有载体的一种很有前途的替代品。一个关键的挑战是确定化学物质是如何被包含和分布在纳米粒子内的，这有助于控制化学物质的保留和释放特性。本研究报告了在由十六烷酸肉豆蔻酯作为固体脂质和 Miglyol 812 作为液体脂质组成的模型脂质纳米粒药物传递系统中，γ-谷维素负载的化学和结构研究。通过高压匀质法在不同的液体脂质含量下制备了脂质纳米粒，与不含γ-谷维素的系统进行了比较。通过光子相关光谱法测量，发现脂质纳米粒的粒径随液体脂质含量的增加而从 200nm 减小到 160nm。对液体脂质的中链甘油三酯的高分辨率质子核磁共振((1)H-NMR)测量证实了液体脂质成功地被包裹在脂质纳米粒中。差示扫描量热法和粉末 X 射线衍射测量结果与((1)H-NMR 互补，其中脂质纳米粒的结晶度随液体脂质含量的增加而降低。对于γ-谷维素在脂质纳米粒内的分布，(1)H-NMR 显示，在负载γ-谷维素的系统中，液体脂质的化学位移比在不含γ-谷维素的系统中发现的更高，表明γ-谷维素被包裹在液体脂质中。此外，原子力显微镜观察到，对于液体脂质含量为 0%的脂质纳米粒，观察到相分离结构，但对于液体脂质含量为 5%和 10%的脂质纳米粒则没有观察到。拉曼光谱和映射测量进一步揭示了γ-谷维素在脂质纳米粒的液体部分而非固体部分的优先掺入。提出了简单的模型，代表了脂质纳米粒系统中γ-谷维素和脂质（固体和液体）的分布。
