Sezanova Kostadinka, Gergulova Rumiana, Shestakova Pavletta, Rabadjieva Diana
Institute of General and Inorganic Chemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., bl. 11, 1113 Sofia, Bulgaria.
Institute of Organic Chemistry with Centre of Phytochemistry, Bulgarian Academy of Sciences, Acad. G. Bonchev Str., bl. 9, 1113 Sofia, Bulgaria.
Biomimetics (Basel). 2024 Jul 25;9(8):455. doi: 10.3390/biomimetics9080455.
Simulated body fluid (SBF) and artificial saliva (AS) are used in biomedical and dental research to mimic the physiological conditions of the human body. In this study, the biomimetic precipitation of double-doped amorphous calcium phosphate in SBF and AS are compared by thermodynamic modelling of chemical equilibrium in the SBF/AS-CaCl-MgCl-ZnCl-KHPO-HO and SBF/AS-CaCl-MgCl-ZnCl-KHPO-Glycine/Valine-HO systems. The saturation indices (SIs) of possible precipitate solid phases at pH 6.5, close to pH of AS, pH 7.5, close to pH of SBF, and pH 8.5, chosen by us based on our previous experimental data, were calculated. The results show possible precipitation of the same salts with almost equal SIs in the two biomimetic environments at the studied pHs. A decrease in the saturation indices of magnesium and zinc phosphates in the presence of glycine is a prerequisite for reducing their concentrations in the precipitates. Experimental studies confirmed the thermodynamic predictions. Only X-ray amorphous calcium phosphate with incorporated Mg (5.86-8.85 mol%) and Zn (0.71-2.84 mol%) was obtained in the experimental studies, irrespective of biomimetic media and synthesis route. Solid-state nuclear magnetic resonance (NMR) analysis showed that the synthesis route affects the degree of structural disorder of the precipitates. The lowest concentration of dopant ions was obtained in the presence of glycine. Further, the behaviour of the selected amorphous phase in artificial saliva was studied. The dynamic of Ca, Mg, and Zn ions between the solid and liquid phases was monitored. Both direct excitation P NMR spectra and H-P CP-MAS spectra proved the increase in the nanocrystalline hydroxyapatite phase upon increasing the incubation time in AS, which is more pronounced in samples with lower additives. The effect of the initial concentration of doped ions on the solid phase transformation was assessed by solid-state NMR.
模拟体液（SBF）和人工唾液（AS）在生物医学和牙科研究中用于模拟人体的生理条件。在本研究中，通过对SBF/AS-CaCl₂-MgCl₂-ZnCl₂-KH₂PO₄-H₂O和SBF/AS-CaCl₂-MgCl₂-ZnCl₂-KH₂PO₄-甘氨酸/缬氨酸-H₂O系统中化学平衡的热力学建模，比较了SBF和AS中双掺杂无定形磷酸钙的仿生沉淀。根据我们之前的实验数据，计算了在pH 6.5（接近AS的pH值）、pH 7.5（接近SBF的pH值）和pH 8.5下可能沉淀固相的饱和指数（SIs）。结果表明，在研究的pH值下，两种仿生环境中几乎具有相同饱和指数的相同盐可能会沉淀。甘氨酸存在下磷酸镁和磷酸锌饱和指数的降低是降低其在沉淀物中浓度的前提条件。实验研究证实了热力学预测。无论仿生介质和合成路线如何，实验研究中仅获得了掺入Mg（5.86 - 8.85 mol%）和Zn（0.71 - 2.84 mol%）的X射线无定形磷酸钙。固态核磁共振（NMR）分析表明，合成路线会影响沉淀物的结构无序程度。在甘氨酸存在下获得了最低浓度的掺杂离子。此外，还研究了所选无定形相在人工唾液中的行为。监测了Ca、Mg和Zn离子在固液相之间的动态。直接激发³¹P NMR光谱和¹H-³¹P CP-MAS光谱均证明，随着在AS中孵育时间的增加，纳米晶羟基磷灰石相增加，在添加剂较少的样品中更为明显。通过固态NMR评估了掺杂离子初始浓度对固相转变的影响。
