The effects of immobilized carboxylic-functional groups on the dynamics of phase transformation from amorphous to octacalcium phosphate

Yuki Sugiura, Kazuo Onuma, Masahiro Nagao, Atsushi Yamazaki

    Research output: Contribution to journalArticle

    8 Citations (Scopus)

    Abstract

    The influence of carboxylic-functional-groups (-COOH) on the phase transformation from amorphous calcium phosphate (ACP) to octacalcium phosphate (OCP) was investigated. 11-Mercaptoundecanoic acid, a carboxylic thiol, was immobilized on gold nanoparticles via covalent bond formation. Time-resolved static light scattering measurements indicated that a structural-reconstruction-type phase transformation occurred with or without the presence of-COOH on the nanoparticles. When it dispersed in calcium phosphate solutions, these nanoparticles inhibited the phase transformation dynamics and also changed the reaction path, forming HPO<inf>4</inf>-OH-layer-deficient OCP at pH 6.5 an intermediate phase, which did not show the typical OCP X-ray diffraction (XRD) peak at 2θ = 4.7°. This phase was not observed in the reference solution containing gold nanoparticles without bound-COOH. The HPO<inf>4</inf>-OH-layer-deficient OCP transformed to conventional OCP gradually, as revealed by XRD, nuclear magnetic resonance, and Raman analyses. Thus, the immobilized-COOH appeared to behave as a negative catalyst, resulting in the formation of the intermediate phase. Such a mechanism partially clarifies complex biomineralization processes, for example teeth enamel and dentin formation, in vivo.

    Original languageEnglish
    Pages (from-to)1624-1632
    Number of pages9
    JournalAmerican Mineralogist
    Volume100
    Issue number7
    DOIs
    Publication statusPublished - 2015 Jul 1

    Keywords

    • Biomineralization
    • calcium phosphate
    • early tooth formation
    • intermediate phase
    • phase transformation

    ASJC Scopus subject areas

    • Geochemistry and Petrology
    • Geophysics

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