TY - JOUR A1 - Hayakawa, S. A1 - Kanaya, T. A1 - Tsuru, K. A1 - Shirosaki, Y. A1 - Osaka, A. A1 - Fujii, E. A1 - Kawabata, K. A1 - Gasqueres, G. A1 - Bonhomme, C. A1 - Babonneau, F. A1 - Jäger, Christian A1 - Kleebe, H.-J. T1 - Heterogeneous structure and in vitro degradation behavior of wet-chemically derived nanocrystalline silicon-containing hydroxyapatite particles JF - Acta biomaterialia N2 - Nanocrystalline hydroxyapatite (HAp) and silicon-containing hydroxyapatite (SiHAp) particles were synthesized by a wet-chemical procedure and their heterogeneous structures involving a disordered phase were analyzed in detail by X-ray diffractometry (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) spectroscopy and solid-state magic-angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy. The effects of heterogeneous structure on in vitro biodegradability and the biologically active Ca(II)- and Si(IV)-releasing property of SiHAp particles were discussed. The 29Si NMR analysis revealed that the Si(IV) was incorporated in the HAp lattice in the form of Q0 (SiO4-4 or HSiO3-4) species, accompanied by the formation of condensed silicate units outside the HAp lattice structure, where the fraction and amount of Q0 species in the HAp lattice depends on the Si content. The 31P and 1H NMR results agreed well with the XRD, TEM and FTIR results. NMR quantitative analysis results were explained by using a core–shell model assuming a simplified hexagonal shape of HAp covered with a disordered layer, where Si(IV) in Q0 was incorporated in the HAp lattice and a disordered phase consisted of hydrated calcium phosphates involving polymeric silicate species and carbonate anions. With the increase in the Si content in the HAp lattice, the in vitro degradation rate of the SiHAps increased, while their crystallite size stayed nearly unchanged. The biologically active Ca(II)- and Si(IV)-releasing ability of the SiHAps was remarkably enhanced at the initial stage of reactions by an increase in the amount of Si(IV) incorporated in the HAp lattice but also by an increase of the amount of polymeric silicate species incorporated in the disordered phase. KW - Silicate KW - Calcium phosphate KW - Hydroxyapatite KW - Degradation KW - Apatite formation PY - 2013 DO - https://doi.org/10.1016/j.actbio.2012.08.024 SN - 1742-7061 VL - 9 IS - 1 SP - 4856 EP - 4867 PB - Elsevier Ltd. CY - Amsterdam AN - OPUS4-27319 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Barheine, Sabrina A1 - Hayakawa, S. A1 - Jäger, Christian A1 - Shirosaki, Y. A1 - Osaka, A. T1 - Effect of disordered structure of boron-containing calcium phosphates on their in vitro biodegradability JF - Journal of the American ceramic society N2 - This study proposes a new guideline for designing biodegradable apatite ceramics. Boron-containing hydroxyapatite (BHAp) particles were prepared by a high-temperature solid-state reaction processing method and were characterized in terms of their chemical composition, apatite lattice defects and in vitro biodegradability. Solid-state nuclear magnetic resonance analysis showed that boron-incorporation into hydroxyapatite (HAp) derived by thermo-chemical reactions between borate and calcium phosphate phases led to disordered phases (BCaP) of a CaO–P2O5–B2O3–OH system covering the crystalline HAp core. X-ray diffraction analysis indicated that the BCaP phase must consist mainly of a crystalline oxyboroapatite (OBAp) phase. An in vitro biodegradability test showed that BHAp degraded quicker than HAp or ß-tricalcium phosphate. The biodegradability of BHAp particles can be controlled by boron incorporation into a HAp lattice leading to the formation of a disordered OBAp phase. KW - Boron KW - Hydroxyapatite KW - Calcium phosphate KW - NMR KW - Biodegradability KW - Disorder KW - Oxyboboapatite PY - 2011 DO - https://doi.org/10.1111/j.1551-2916.2011.04400.x SN - 0002-7820 SN - 1551-2916 VL - 94 IS - 8 SP - 2656 EP - 2662 PB - Blackwell Publishing CY - Malden AN - OPUS4-26244 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -