A Systematic Study of the Effect of pH on the Initialization of Ca-deficient Hydroxyapatite to β-TCP Nanoparticles

Abstract

The formation of β-tricalcium phosphate (β-TCP) nanoparticles via a wet precipitation technique was studied in a systematical way, taking reaction pH and sintering temperature parameters into account. A full transformation of Ca-deficient hydroxyapatite (CDHA) to β-TCP at 750 °C in under 3 h from Ca++ and PO43− precursor solutions prepared under a pH of 5.5 was observed. For pH values higher than 6.5, CDHA can only partially transform into β-TCP and only at temperatures higher than 750 °C confirmed using X-Ray diffraction and Raman spectroscopy. The morphologies of the particles were also examined by Transmission electron microscopy. The lower temperatures and the shorter sintering time allow for a fine needle-like morphology, but with a high crystallinity, likely eliminating the possibility of excessive grain growth that is otherwise expected to occur under high-temperature treatment with long process times. We show that sintering of nanostructured, high crystallinity β-TCP at relatively low temperatures is possible via adjustment of the precursor solution parameters. Such an outcome is important for the use of β-TCP with a fine morphology imitating that of the skeletal tissues, enhancing the osteointegration of a base, load-bearing alloy to the host tissue. MTT analysis was used to test the effect of the obtained β-TCP particles on the viability of MG-63 human osteoblast-like cells.

Calcium-Rich 13X Zeolite as a Filler with Remineralizing Potential for Dental Composites

“…New peaks are marked in Figure with a * at ∼26° and between 32 and 35°. These peaks are characteristic for the hydroxyapatite crystallographic structure. − Peaks are not sharp, which indicates that nanohydroxyapatite was obtained on the surface . The appearance of new peaks does not result in the disappearance of those peaks that occur in the initial sample.…”

Determination of the Activation Energies of Phase Transition for Calcium Orthophosphates Based on Powder X‐Ray Diffraction Data

“…where K is a constant equal to 0.24, used for different hydroxyapatite in powder diffraction, and Bhkl is the width (hkl) of the reflex at its half-height 16 .…”

“…where K is a constant equal to 0.24, used for different hydroxyapatite in powder diffraction, and B hkl is the width (hkl) of the reflex at its halfheight. [22] The solubility of calcium phosphate precipitates was calculated by using the formula for the solubility product, as 10 (6𝛼 3 S) 6 (S + C OH ) 2 (7) where S is the solubility (mol/l), 𝛼 i and 𝛽 i are the proportions of anions and cations of the precipitate. Similarly, K 1 , K 2 , and K 3 are acid dissociation constants, K 1 * and K 2 * are stability constants of the cation hydroxy complexes.…”

Synthesis and in Vitro Toxicity Assessment of Different Nano-Calcium Phosphate Nanoparticles

“…Among CaPs, HA is the most stable and less soluble phase, therefore, low biodegradability of HA within the body might limit some of the applications. When compared to HA, β-TCP shows better biodegradability, thus it can be absorbed better and take over by newly generated hard tissues [10]. Since BCP contains a stable apatite phase (HA) and a more soluble/biodegradable phase (β-TCP) together, it is promising for many medical applications.…”

“…In chemical reactions, both BCP and β-TCP can be reconstructed from a non-stoichiometric apatite during heat treatment at above 700°C [11]. The crystal structure of nonstoichiometric apatite is similar to HA whereas, it is chemically and compositionally similar to β-TCP [10]. In vitro studies have revealed that BCP and β-TCP are biocompatible in many cell lines, such as the dog GRAPHICAL ABSTRACT periodontal ligament cells [12], human bone marrow stromal cells (hBMSCs) [13], human osteoblast-like cells (SaOS-2) [14], osteoblasts (SaOs-2 and MC3T3-E1 cells) [15], MC3T3-E1 osteoblast-like cells [16] and human lymphocyte cells [17].…”