Division of Nanotechnology and Functional Materials, Department of Engineering Sciences , Uppsala University , SE-751 21 Uppsala , Sweden.
Department of Materials and Environmental Chemistry , Stockholm University , SE-106 91 Stockholm , Sweden.
ACS Appl Mater Interfaces. 2018 Jun 27;10(25):21556-21564. doi: 10.1021/acsami.8b03939. Epub 2018 Jun 13.
Amorphous calcium carbonate (ACC), with the highest reported specific surface area of all current forms of calcium carbonate (over 350 m g), was synthesized using a surfactant-free, one-pot method. Electron microscopy, helium pycnometry, and nitrogen sorption analysis revealed that this highly mesoporous ACC, with a pore volume of ∼0.86 cm g and a pore-size distribution centered at 8-9 nm, is constructed from aggregated ACC nanoparticles with an estimated average diameter of 7.3 nm. The porous ACC remained amorphous and retained its high porosity for over 3 weeks under semi-air-tight storage conditions. Powder X-ray diffraction, large-angle X-ray scattering, infrared spectroscopy, and electron diffraction exposed that the porous ACC did not resemble any of the known CaCO structures. The atomic order of porous ACC diminished at interatomic distances over 8 Å. Porous ACC was evaluated as a potential drug carrier of poorly soluble substances in vitro. Itraconazole and celecoxib remained stable in their amorphous forms within the pores of the material. Drug release rates were significantly enhanced for both drugs (up to 65 times the dissolution rates for the crystalline forms), and supersaturation release of celecoxib was also demonstrated. Citric acid was used to enhance the stability of the ACC nanoparticles within the aggregates, which increased the surface area of the material to over 600 m g. This porous ACC has potential for use in various applications where surface area is important, including adsorption, catalysis, medication, and bone regeneration.
无定形碳酸钙（ACC）具有所有当前碳酸钙形式中最高的比表面积（超过 350 m²/g），它是使用无表面活性剂的一锅法合成的。电子显微镜、氦比重瓶和氮气吸附分析表明，这种高度中孔的 ACC，具有约 0.86 cm³/g 的孔体积和集中在 8-9 nm 的孔径分布，是由聚集体的 ACC 纳米粒子构建而成，其估计平均直径为 7.3nm。多孔 ACC 在半密封储存条件下保持无定形且保留其高孔隙率超过 3 周。粉末 X 射线衍射、大角度 X 射线散射、红外光谱和电子衍射表明，多孔 ACC 与任何已知的 CaCO 结构都不相似。多孔 ACC 的原子有序性在超过 8Å 的原子间距离处减弱。多孔 ACC 被评估为体外难溶性物质的潜在药物载体。伊曲康唑和塞来昔布在材料的孔内保持无定形形式稳定。两种药物的释放速率都显著提高（高达结晶形式的溶解速率的 65 倍），并证明了塞来昔布的超饱和释放。柠檬酸被用于增强团聚体中 ACC 纳米粒子的稳定性，这将材料的表面积提高到超过 600 m²/g。这种多孔 ACC 在各种需要表面积的应用中具有潜在用途，包括吸附、催化、药物和骨再生。
