A Comparative Study of the Sintering Behavior of Pure and Iron-Substituted Hydroxyapatite

Abstract

Hydroxyapatite (HA) is a widely studied biomaterial for bone grafting and tissue engineering applications. The crystal structure of HA lends itself to a wide variety of substitutions, which allows for tailoring of material properties. Iron is of interest in ion substitution in HA due to its magnetic properties. The synthesis and characterization of iron-substituted hydroxyapatite (FeHA) have been widely studied, but there is a lack of studies on the sintering behaviors of FeHA materials compared to pure HA. Studying the sintering behavior of a substituted apatite provides information regarding how the substitution affects material characteristics such as stability and bulk mechanical properties, thereby providing insight into which applications are appropriate for the substituted material. In this study both pure HA and FeHA were synthesized, pressed into pellets, and then sintered at temperatures ranging from 900-1300°C and 600-1100°C, respectively. The study thoroughly examined the comparative sintering behaviors of the two materials using density measurements, mechanical testing, X-ray diffraction, and electron microscopy. It was found that FeHA is considerably less thermally stable than pure HA, with decomposition beginning around 1200°C for pure HA samples, while at 700°C for the FeHA. The FeHA also had a much lower mechanical strength than that of the pure HA. An in vitro cell culture study was conducted by immersing FeHA powder in cell culture media, with HA powder at equivalent doses as a control, verified that FeHA is a biocompatible material. Although the FeHA would be unsuitable for bulk applications, it is a potential material for a variety of biomedical applications including drug delivery, cancer hyperthermia, and bone tissue engineering composites.

A Comparative Study of the Sintering and Cell Behavior of Pure and Cobalt Substituted Hydroxyapatite

“…This is likely a result of an earlier onset of decomposition and formation of blowholes in CoHA than in HA. A similar result was also observed for ironsubstituted HA, which decomposed at 700°C [32]. In addition to the density and mechanical property measurements, it is clear from visual inspection that the CoHA pellets have a different sintering behavior than the pure HA.…”

A Comparative Study of the Sintering Behavior of Pure and Manganese-Substituted Hydroxyapatite

“…Sintering at 1200 °C, the HA phase has almost completely decomposed with α-TCP, β-TCP, and Mn 3 O 4 being the dominate phases. The flexural strength of β-TCP is weaker than natural bone and is often detrimental to the mechanical properties of HA when presents as an impurity [ 53 , 57 ]. The maximum observed M.O.R of MnHA of 64 MPa compares favorably with literature values.…”

"Design of Hydroxyapatite/Magnetite (Hap/Fe3O4) Based Composites Reinforced with ZnO and MgO for Biomedical Applications"

“…It is commonly used in bone grafting and tissue engineering applications due to its excellent biocompatibility and osteon-conductivity [9]. HAP, Ca 10 (PO4) 6 (OH) 2 , has a hexagonal crystal lattice structure [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28], which allows for a wide variety of substitutions by anions, cations, and functional groups, such as the F- [11], Fe 2+/3+ [4,[12][13][14][15][16], and [17]. Iron is of interest as a cation that can be substituted in HAP due to the fact it is naturally present in trace amounts in both teeth and bone [13].…”

“…Iron is of interest as a cation that can be substituted in HAP due to the fact it is naturally present in trace amounts in both teeth and bone [13]. Furthermore, its presence provides iron substituted apatite (FeHA) with possible magnetic properties that can potentially be applied to various applications, including drug delivery, medical imaging, or hyperthermia based cancer therapies, for which pure HAP is unsuitable [1,14,[18][19][20][21][22]. Magnetic therapy has been considered as a promising treatment alternative in health care, especially in the treatment of bone diseases.…”