Hydrothermal synthesis and characterization of hydroxyapatite and fluorhydroxyapatite nano-size powders

Abstract

Pure hydroxyapatite (HAp) and fluoride-containing apatite powders (FHAp) were synthesized using a hydrothermal method. The powders were assessed by x-ray diffraction (XRD), Fourier transform infrared (FTIR), scanning electron microscope (SEM) and F-selective electrode. X-ray diffraction results revealed the formation of single phase apatite structure for all the compositions synthesized in this work. However, the addition of a fluoride ion led to a systematic shift in the (3 0 0) peak of the XRD pattern as well as modifications in the FTIR spectra. It was found that the efficiency of fluoride ion incorporation decreased with the increase in the fluoride ion content. Fluorine incorporation efficiency was around 60% for most of the FHAp samples prepared in the current study. Smaller and less agglomerated particles were obtained by fluorine substitution. The bioactivity of the powder samples with different fluoride contents was compared by performing cell proliferation, alkaline phosphatase (ALP) and Alizarin red staining assays. Human osteoblast cells were used to assess the cellular responses to the powder samples in this study. Results demonstrated a strong dependence of different cell activities on the level of fluoridation.

Effects of fluoridation of porcine hydroxyapatite on osteoblastic activity of human MG63 cells

“…Furthermore, with the increasing degree of fluoridation, the intensity of the OH characteristic band at 3573 cm −1 became weaker, while the other band at 3544 cm −1 attributed to hydrogen interacting with fluorine became stronger [25, 26]. Similarly, another major change in the FTIR spectra of FPHA was that the absorption band attributed to OH around 634 cm −1 disappeared, and was replaced by another band around 742 cm −1 attributed to OH interacting with fluorine [26, 27], which was further evidence for fluoride incorporation (figure 2(c)).…”

“…The results of FTIR in the present study further confirmed that fluoride substituted for hydroxyl groups in the apatite crystal structure. Also, the fluoride substituted for hydroxyls causes the shift of the reflection in the XRD pattern [25, 27]. Previous studies on the dissolution behavior of synthetic FHA were mainly based on deionized water [16, 18, 26], physiological saline solution [17, 25] and simulated body fluid [28], which could not simulate the in vivo environment of implant biomaterial appropriately.…”

Calcium orthophosphates (CaPO 4 ): Occurrence and properties

“…Such compounds are called fluorhydroxyapatites (FHA) (Nikcevic et al 2004;Montazeri et al 2010;Zhu et al 2012) or hydroxyfluorapatites (HFA) (Rodríguez-Lorenzo et al 2003;Azami et al 2012) and described with a chemical formula Ca 10 (PO 4 ) 6 (-OH) 2-x F x , where 0 \ x \ 2. If the F/OH ratio is either uncertain or not important, the chemical formula of FHA and HFA is often written as Ca 10 (PO 4 ) 6 (F,OH) 2 .…”

The role of TiO2, ZrO2, BaO and SiO2 on the mechanical properties and crystallization behavior of fluorapatite–mullite glass–ceramics

“…Fluorapatite is a bioactive compound with an apatite-like structure, in which OH groups have been substituted by fluorine ones. Furthermore, its crystalline structure is more stable than hydroxyapatite, which is an important issue where bioactivity receives attention based on crystalline stability [1][2][3]. Similarity between hardness of fluorapatite-based glass-ceramics and tooth enamel is another advantage that makes them new candidates for substitution of hydroxyapatite in restorative dentistry [1][2][3].…”

“…Following the precipitation of apatite in these droplets, changing the composition of the residual glass phase leads to the precipitation of mullite [4,5,8]. In these specimens fluorapatite is responsible to link to the tooth enamel and bone [3] and mullite induces adequate mechanical properties [10]. The latter phase plays a key role in biocompatible glass-ceramics since they are mostly planned to use in the stress bearing areas [2].…”