Department of Pharmaceutical Technology, Graduate School of Medical and Pharmaceutical Science , University of Toyama , 2630 Sugitani , Toyama-shi , Toyama 930-0194 , Japan.
Department of Pharmaceutics , Hoshi University , 2-4-41 Ebara , Shinagawa-ku , Tokyo 142-8501 , Japan.
Langmuir. 2018 Oct 9;34(40):12093-12099. doi: 10.1021/acs.langmuir.8b02410. Epub 2018 Sep 27.
The purpose of the present study is to demonstrate the applicability of magnetic resonance imaging, especially T relaxation time mapping, for nondestructive monitoring of the dispersion state of nanoparticles (NPs) in concentrated suspensions. TiO 15-nm-diameter NPs, for use in sunscreen lotion products, were examined as a test NP. First, this study investigated whether T is sensitive to the NP concentration. In experiments with pulsed nuclear magnetic resonance on TiO NP suspensions with different organic solvents (ethanol, acetone, and decamethylcyclopentasiloxane), the T of each solvent varied in the suspensions according to the NP concentration. This study also confirmed that T mapping was effective for visualizing differences in NP concentration. Subsequently, gravitational sedimentation of the test suspensions was investigated. T mapping exhibited better detection sensitivity to sedimentation occurring in concentrated suspensions than visual observation, as it enabled the detection of changes in NP distributions that could not be visible to the naked eye. In addition, measurements of backscattered light enabled the full understanding of the dispersion stability of the TiO NPs in each solvent. Finally, the present study evaluated the centrifuge sedimentation of a commercial TiO NP suspension. T mapping clearly showed the complicated sedimentation behavior induced by the centrifugation treatment. The simulated fluid flow was consistent with the particle distribution in the centrifuged sample; thus, the sedimentation was believed to have developed in accordance with the vorticity generated by the centrifugation.
本研究旨在展示磁共振成像（尤其是 T 弛豫时间成像）在纳米颗粒（NP）在浓缩悬浮液中分散状态的无损监测中的适用性。以用于防晒霜产品的 15nm 直径 TiO2 NP 作为测试 NP。首先，本研究考察了 T 是否对 NP 浓度敏感。在使用脉冲核磁共振对具有不同有机溶剂（乙醇、丙酮和十甲基环五硅氧烷）的 TiO2 NP 悬浮液进行的实验中，根据 NP 浓度，每种溶剂的 T 在悬浮液中发生变化。本研究还证实了 T 成像对于可视化 NP 浓度差异是有效的。随后，考察了测试悬浮液的重力沉降。与肉眼观察相比，T 成像对浓缩悬浮液中发生的沉降具有更好的检测灵敏度，因为它能够检测到肉眼无法看到的 NP 分布变化。此外，背散射光的测量能够充分理解每种溶剂中 TiO2 NP 的分散稳定性。最后，本研究评估了商业 TiO2 NP 悬浮液的离心沉降。T 成像清楚地显示了离心处理引起的复杂沉降行为。模拟的流体流动与离心样品中的颗粒分布一致；因此，认为沉降是根据离心产生的涡度发展的。
