Department of Materials Science and Engineering, University of Alabama at Birmingham, AL 35294, USA.
Acta Biomater. 2010 Aug;6(8):3234-41. doi: 10.1016/j.actbio.2010.02.031. Epub 2010 Feb 25.
Owing to its resemblance to the major inorganic constituent of bone and tooth, hydroxyapatite is recognized as one of the most biocompatible materials and is widely used in systems for bone replacement and regeneration. In this study the pulsed laser deposition technique was chosen to produce hydroxyapatite with different crystallographic orientations in order to investigate some of the material properties, including its in vitro dissolution behavior, as well as mechanical properties. The crystallographic orientations of hydroxyapatite coatings can be carefully controlled, mainly by varying the energy density of the KrF excimer laser (248 nm) used for deposition. Nanoindentation results showed that highly c-axis oriented hydroxyapatite coatings have higher hardness and Young's modulus values compared with the values of randomly oriented coatings. After 24h immersion in simulated physiological solution the overall surface morphology of the highly oriented coatings was dramatically altered. The porosity was drastically increased and sub-micron pores were formed throughout the coatings, whereas the average size of the grains in the coatings was not significantly changed. The composition of the textured hydroxyapatite coatings remained essentially unchanged. Their c-axis texture, on the other hand, was rather enhanced with an increase in immersion time. The c-axis oriented hydroxyapatite surfaces are likely to promote preferentially oriented growth through a cyclic process of dissolution and reprecipitation, followed by homoepitaxial growth. The remarkable morphological and microstructural changes after dissolution suggest a capability of highly textured hydroxyapatite as a tissue engineering scaffold with an interconnecting porous network that may be beneficial for cellular activity.
由于其类似于骨和牙的主要无机成分，羟基磷灰石被认为是最具生物相容性的材料之一，并广泛应用于骨替代和再生系统。在这项研究中，选择脉冲激光沉积技术来制备具有不同结晶取向的羟基磷灰石，以研究一些材料性能，包括其体外溶解行为以及机械性能。羟基磷灰石涂层的结晶取向可以通过改变用于沉积的 KrF 准分子激光（248nm）的能量密度来进行精细控制。纳米压痕结果表明，高度 c 轴取向的羟基磷灰石涂层具有比随机取向涂层更高的硬度和杨氏模量值。在模拟生理溶液中浸泡 24 小时后，高度取向涂层的整体表面形貌发生了显著变化。孔隙率急剧增加，亚微米级的孔在整个涂层中形成，而涂层中晶粒的平均尺寸没有明显变化。织构化羟基磷灰石涂层的组成基本保持不变。另一方面，其 c 轴织构随着浸泡时间的增加而得到增强。c 轴取向的羟基磷灰石表面可能通过溶解和再沉淀的循环过程促进优先取向生长，然后进行同质外延生长。溶解后显著的形态和微观结构变化表明，高度织构化的羟基磷灰石具有作为组织工程支架的能力，具有相互连接的多孔网络，这可能有利于细胞活性。
