1 research outputs found
Amorphous Calcium Carbonate Constructed from Nanoparticle Aggregates with Unprecedented Surface Area and Mesoporosity
Amorphous
calcium carbonate (ACC), with the highest reported specific
surface area of all current forms of calcium carbonate (over 350 m<sup>2</sup> g<sup>ā1</sup>), 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 ā¼0.86 cm<sup>3</sup> g<sup>ā1</sup> and
a pore-size distribution centered at 8ā9 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<sub>3</sub> structures. The atomic order of
porous ACC diminished at interatomic distances over 8 Ć
. 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<sup>2</sup> g<sup>ā1</sup>. This porous ACC has potential for use in various applications where
surface area is important, including adsorption, catalysis, medication,
and bone regeneration