Egami Kiichi, Higashi Kenjirou, Yamamoto Keiji, Moribe Kunikazu
Graduate School of Pharmaceutical Sciences, Chiba University, 1-8-1 Inohana, Chuo-ku, Chiba 260-8675, Japan.
Mol Pharm. 2015 Aug 3;12(8):2972-80. doi: 10.1021/acs.molpharmaceut.5b00236. Epub 2015 Jul 7.
The crystallization behavior of a pharmaceutical drug in nanoparticles was directly evaluated by atomic force microscopy (AFM) force curve measurements in aqueous solution. A ternary spray-dried sample (SPD) was prepared by spray drying the organic solvent containing probucol (PBC), hypromellose (HPMC), and sodium dodecyl sulfate (SDS). The amorphization of PBC in the ternary SPD was confirmed by powder X-ray diffraction (PXRD) and solid-state 13C NMR measurements. A nanosuspension containing quite small particles of 25 nm in size was successfully prepared immediately after dispersion of the ternary SPD into water. Furthermore, solution-state 1H NMR measurements revealed that a portion of HPMC coexisted with PBC as a mixed state in the freshly prepared nanosuspension particles. After storing the nanosuspension at 25 °C, a gradual increase in the size of the nanoparticles was observed, and the particle size changed to 93.9 nm after 7 days. AFM enabled the direct observation of the morphology and agglomeration behavior of the nanoparticles in water. Moreover, AFM force-distance curves were changed from (I) to (IV), depending on the storage period, as follows: (I) complete indentation within an applied force of 1 nN, (II) complete indentation with an applied force of 1-5 nN, (III) partial indentation with an applied force of 5 nN, and (IV) nearly no indentation with an applied force of 5 nN. This stiffness increase of the nanoparticles was attributed to gradual changes in the molecular state of PBC from the amorphous to the crystal state. Solid-state 13C NMR measurements of the freeze-dried samples demonstrated the presence of metastable PBC Form II crystals in the stored nanosuspension, strongly supporting the AFM results.
通过水溶液中的原子力显微镜（AFM）力曲线测量直接评估了药物在纳米颗粒中的结晶行为。通过喷雾干燥含有普罗布考（PBC）、羟丙甲纤维素（HPMC）和十二烷基硫酸钠（SDS）的有机溶剂制备了三元喷雾干燥样品（SPD）。通过粉末X射线衍射（PXRD）和固态13C NMR测量证实了三元SPD中PBC的非晶化。将三元SPD分散到水中后，立即成功制备出了含有尺寸为25 nm的非常小颗粒的纳米悬浮液。此外，溶液态1H NMR测量表明，在新制备的纳米悬浮颗粒中，一部分HPMC与PBC以混合状态共存。将纳米悬浮液在25℃下储存后，观察到纳米颗粒尺寸逐渐增加，7天后粒径变为93.9 nm。AFM能够直接观察水中纳米颗粒的形态和团聚行为。此外，AFM力-距离曲线根据储存时间从（I）变为（IV），如下：（I）在1 nN的作用力下完全压入，（II）在1 - 5 nN的作用力下完全压入，（III）在5 nN的作用力下部分压入，（IV）在5 nN的作用力下几乎没有压入。纳米颗粒这种硬度的增加归因于PBC分子状态从非晶态到晶态的逐渐变化。对冻干样品的固态13C NMR测量表明，在储存的纳米悬浮液中存在亚稳的PBC晶型II晶体，有力地支持了AFM结果。
