Uskoković Vuk
Advanced Materials and Nanobiotechnology Laboratory, Department of Bioengineering, University of Illinois, Chicago, IL 60607-7052, USA.
RSC Adv. 2015;5:36614-36633. doi: 10.1039/C4RA17180B.
Mysteries surrounding the most important mineral for the vertebrate biology, hydroxyapatite, are many. Perhaps the Greek root of its name, απαταo, meaning 'to deceive' and given to its mineral form by the early gem collectors who confused it with more precious stones, is still applicable today, though in a different connotation, descriptive of a number of physicochemical peculiarities exhibited by it. Comparable to water as the epitome of peculiarities in the realm of liquids, hydroxyapatite can serve as a paradigm for peculiarities in the world of solids. Ten of the peculiar properties of hydroxyapatite are sketched in this review piece, ranging from (i) the crystal lattice flexibility to (ii) notorious surface layer instability to (iii) finite piezoelectricity, pyroelectricity and conductivity to protons to (iv) accelerated growth and improved osteoconductivity in the electromagnetic fields to (v) high nucleation rate at low supersaturations and low crystal growth rate at high supersaturations to (vi) higher bioactivity and resorbability of biological apatite compared to the synthetic ones, and beyond. An attempt has been made to explain this array of curious characteristics by referring to a particular element of the crystal structure of hydroxyapatite: the hydroxyl ion channel extending in the direction of the c-axis, through a crystallographic column created by the overlapping calcium ion triangles.
围绕脊椎动物生物学中最重要的矿物质——羟基磷灰石的谜团众多。也许它名字的希腊语词根απαταo，意为“欺骗”，是早期宝石收藏家赋予其矿物形态的，他们将其与更珍贵的宝石混淆，如今这个词根或许仍适用，只是含义不同，用来描述它所展现出的一些物理化学特性。与水作为液体领域特性的典范类似，羟基磷灰石可作为固体世界特性的范例。本文综述了羟基磷灰石的十种特性，从（i）晶格柔韧性到（ii）臭名昭著的表面层不稳定性，从（iii）有限的压电性、热电性和质子导电性到（iv）在电磁场中加速生长和改善骨传导性，从（v）低过饱和度下的高成核率和高过饱和度下的低晶体生长速率到（vi）生物磷灰石相比合成磷灰石具有更高的生物活性和可吸收性等等。本文试图通过提及羟基磷灰石晶体结构的一个特定元素来解释这一系列奇特特性：沿c轴方向延伸的羟基离子通道，它穿过由重叠的钙离子三角形形成的晶体学柱。
