Isolating the Effects of Mg2+, Mn2+ and Sr2+ Ions on Osteoblast Behavior from those Caused by Hydroxyapatite Transformation

Ionic trace elements such as Mg2+, Mn2+ and Sr2+ are very difficult to stabilize in the hydroxyapatite lattice, and they can induce phase transformations when subjected to thermal treatments. The effects of the ions themselves are often confused with the effects of the newly formed phases. Therefore, the objective of this work was to evaluate the effects of the ions isolated from the effects caused by the inherent phase transformations observed in these systems. WDXRF, XRD, FTIR and biological assays using mouse preosteoblastic cells (MC3T3-E1) showed the Mg2+ ions can stimulate cell differentiation even when segregated from the HA structure in the form of MgO. However, the presence of MgO considerably retards cell proliferation. At the same time, Mn2+ ions are able to increase cell proliferation and induce the production of high levels of ALP, regardless of whether they are inserted into the HA structure or segregated in the form of Mn3O4. Finally, the presence of Sr2+ in the HA lattice does not appear to directly affect cell behavior, since both the proliferation and production of ALP are comparable to those observed in the nondoped HA sample.

诸如Mg²+、Mn²+与Sr²+在内的离子型微量元素，在羟基磷灰石（hydroxyapatite, HA）晶格中极难稳定存在，且在经受热处理时会诱导物相转变；这类离子自身的作用常与新生成物相带来的效应相混淆，因此本研究的目标在于剥离该类体系中固有物相转变所引发的效应，以单独评估离子本身的作用。通过波长色散X射线荧光光谱法（Wavelength Dispersive X-ray Fluorescence Spectrometry, WDXRF）、X射线衍射法（X-ray Diffraction, XRD）、傅里叶变换红外光谱法（Fourier Transform Infrared Spectroscopy, FTIR），以及以小鼠前成骨细胞（MC3T3-E1）开展的生物学实验，研究结果显示：即便Mg²+以氧化镁（MgO）的形式脱离HA晶格结构，仍可刺激细胞分化，但氧化镁的存在会显著抑制细胞增殖；与此同时，无论Mn²+是嵌入HA晶格，还是以四氧化三锰（Mn3O4）的形式游离存在，均能够促进细胞增殖，并诱导高水平碱性磷酸酶（Alkaline Phosphatase, ALP）的生成；最终研究表明，Sr²+在HA晶格中的存在似乎不会直接影响细胞行为，因为细胞增殖与ALP生成水平均与未掺杂HA样品中的观测结果相当。