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Home  >  Journal list  >  Journal of the Ceramic Society of Japan  >  Vol.122  No.1428 (August) (2014)  >  pp.679-687

Journal of the Ceramic Society of Japan
<<Previous article Vol.122  No.1428 (August) (2014)   pp.679 - 687 Next article>>

Dissolution behavior of vaterite spherulite in solutions containing phosphate ions

Yuki SUGIURA1), Kazuo ONUMA2), Masahiro NAGAO1), Koichi MOMMA3), Yuki KIMURA4), Atsushi YAMAZAKI1)
1) Department of Environmental and Resources Engineering, School of Creative Science and Technology, Waseda University 2) National Institute of Advanced Industrial Science and Technology 3) Department of Geology and Paleontology, National Museum of Nature and Science 4) Institute of Low Temperature Science, Hokkaido University

Vaterite is a crystalline polymorph of calcium carbonate that exhibits low stability in comparison with the other crystalline polymorphs of calcium carbonate. It often assumes a spherical shape. The physical properties of vaterite are utilized in advanced biomaterials such as drug delivery systems (DDSs). The potential application of vaterite in DDSs demands a comprehensive understanding of its dissolution rate as a function of PO4 concentration. Using in situ optical studies, we analyzed the dissolution behavior of vaterite in a simulated PO4-containing biogenic environment. The varying physicality (i.e., the pseudo-physiological conditions) of vaterite were investigated using high-resolution cryogenic transmission electron microscopy and small-angle X-ray scattering. In addition, we measured the PO4/Ca ratio in each part of vaterite spherulites using field-emission scanning electron microscopy in conjunction with energy-dispersive X-ray spectroscopy and inductively coupled plasma atomic emission spectrometry.
We categorized the vaterite spherulites into three parts—the shell, mantle, and core parts—on the basis of their dissolution behavior and PO4 response. The PO4 response to the dissolution dynamics increases toward the outer part, although the adsorption rate decreases in the presence of PO4 and PO4 fluorescence materials. The composition of the shell part was nearly identical to that of ideal vaterite, whereas the inner part exhibited a high C/Ca ratio and a poorly crystalline phase referred to as vaterite-like material. The dissolution rate of each part was 0.23–1.58 nm/s (shell), 0.63–3.19 nm/s (mantle), and 1.38–5.71 nm/s (core). The vaterite and vaterite-like materials were further identified according to their composition and particle size distribution.


Keyword:
Vaterite, Calcium carbonate, Phosphate, Spherulite, Biomaterial, Drug delivery systems

Received: April 18, 2014
Accepted: May 25, 2014 , Published online: August 01, 2014

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