Physical Chemistry, Lund University, P.O. Box 124, SE-22100 Lund, Sweden.
Langmuir. 2012 Jul 24;28(29):10688-96. doi: 10.1021/la301579g. Epub 2012 Jul 11.
Controlling the interfacial behavior and properties of lipid liquid crystalline nanoparticles (LCNPs) at surfaces is essential for their application for preparing functional surface coatings as well as understanding some aspects of their properties as drug delivery vehicles. Here we have studied a LCNP system formed by mixing soy phosphatidylcholine (SPC), forming liquid crystalline lamellar structures in excess water, and glycerol dioleate (GDO), forming reversed structures, dispersed into nanoparticle with the surfactant polysorbate 80 (P80) as stabilizer. LCNP particle properties were controlled by using different ratios of the lipid building blocks as well as different concentrations of the surfactant P80. The LCNP size, internal structure, morphology, and charge were characterized by dynamic light scattering (DLS), synchrotron small-ange X-ray scattering (SAXS), cryo-transmission electron microscopy (cryo-TEM), and zeta potential measurements, respectively. With increasing SPC to GDO ratio in the interval from 35:65 to 60:40, the bulk lipid phase structure goes from reversed cubic micellar phase with Fd3m space group to reversed hexagonal phase. Adding P80 results in a successive shift toward more disorganized lamellar type of structures. This is also seen from cryo-TEM images for the LCNPs, where higher P80 ratios results in more extended lamellar layers surrounding the inner, more dense, lipid-rich particle core with nonlamellar structure. When put in contact with a solid silica surface, the LCNPs adsorb to form multilayer structures with a surface excess and thickness values that increase strongly with the content of P80 and decreases with increasing SPC:GDO ratio. This is reflected in both the adsorption rate and steady-state values, indicating that the driving force for adsorption is largely governed by attractive interactions between poly(ethylene oxide) (PEO) units of the P80 stabilizer and the silica surface. On cationic surface, i.e., silica modified with 3-aminopropltriethoxysilane (APTES), the slightly negatively charged LCNPs give rise to a very significant adsorption, which is relatively independent of LCNP composition. Finally, the dynamic thickness measurements indicate that direct adsorption of intact particles occurred on the cationic surface, while a slow buildup of the layer thickness with time is seen for the weakly interacting systems.
控制脂质液晶纳米颗粒（LCNP）在表面的界面行为和性质对于它们在制备功能性表面涂层中的应用以及理解作为药物输送载体的某些性质至关重要。在这里，我们研究了由混合大豆卵磷脂（SPC）形成的 LCNP 系统，在过量水中形成液晶层状结构，以及甘油二油酸酯（GDO），形成反向结构，分散到纳米颗粒中，表面活性剂聚山梨酯 80（P80）作为稳定剂。通过使用不同比例的脂质构建块以及不同浓度的表面活性剂 P80 来控制 LCNP 颗粒的性质。通过动态光散射（DLS）、同步小角 X 射线散射（SAXS）、冷冻传输电子显微镜（cryo-TEM）和 zeta 电位测量分别对 LCNP 粒径、内部结构、形态和电荷进行了表征。随着 SPC 与 GDO 比例从 35:65 增加到 60:40，大块脂质相结构从具有 Fd3m 空间群的反向立方胶束相转变为反向六方相。添加 P80 导致结构向更加无序的层状类型连续转变。这也可以从 LCNP 的 cryo-TEM 图像中看出，其中较高的 P80 比例导致围绕内部更密集、富含脂质的颗粒核心的更扩展的层状层具有非层状结构。当与固体二氧化硅表面接触时，LCNP 吸附形成具有表面过剩和厚度值的多层结构，该值随着 P80 和 SPC:GDO 比例的增加而强烈增加。这反映在吸附速率和稳态值上，表明吸附的驱动力主要由 P80 稳定剂的聚（环氧乙烷）（PEO）单元与二氧化硅表面之间的吸引力控制。在阳离子表面上，即经过 3-氨丙基三乙氧基硅烷（APTES）修饰的二氧化硅，带轻微负电荷的 LCNP 引起非常显著的吸附，该吸附相对独立于 LCNP 组成。最后，动态厚度测量表明，完整颗粒直接在阳离子表面上吸附，而对于弱相互作用体系，随着时间的推移，层厚度的缓慢增加。
