Manipulation of Mg²⁺–Ca²⁺ Switch on the Development of Bone Mimetic Hydroxyapatite

Abstract

Ionic substitution can affect essential physicochemical properties leading to a specific biological behavior upon implantation. Therefore, it has been proposed as a tool to increase the biological efficiency of calcium phosphate based materials. In the following study, we have evaluated the contribution of an important cation in nature, Mg, into the structure of previously studied biocompatible and biodegradable hydroxyapatite (HA) nanorods and its subsequent effect on its chemical, morphology, and bone mimetic articulation. Mg-substituted HA samples were synthesized by an aqueous wet-chemical precipitation method, followed by an hydrothermal treatment involving a Mg precursor that partially replace Ca ions into HA crystal lattice; Mg concentrations were modulated to obtain a nominal composition similar to that exists in calcified tissues. Hydrothermally synthesized Mg-substituted HA nanoparticles were characterized by X-ray powder diffraction, FT-NIR and EDX spectroscopies, field emission scanning and high resolution transmission electron microscopies (FE-SEM, H-TEM). Molecular modeling combining ab initio methods and power diffraction data were also performed. Results showed that Mg-substitution promoted the formation of calcium deficient HA (cdHA) where Mg replacement is energetically favored at Ca(1) position in a limited and specific amount directing the additional Mg toward the surface of the crystal. The control of Mg incorporation into HA nanorods gave rise to a tailored crystallinity degree, cell parameters, morphology, surface hydration, solubility, and degradation properties in a dose-replacement dependent manner. The obtained materials show qualities that conjugated together to drive an optimal in vitro cellular viability, spreading, and proliferation confirming their biocompatibility. In addition, an improved adhesion of osteoblast was evidenced after Mg-Ca substitution.

Effect of the crystal size on the infrared and Raman spectra of bio hydroxyapatite of human, bovine, and porcine bones

“…The raw samples exhibited broad peaks, and after calcination, their width decreases. Figure shows that raw samples are constituted by ordered crystals; consequently, their peak widths are the result of elastic and inelastic diffraction contributions and are not due to a low crystalline quality (order) as have been previously pointed out . It is clear that if the raw crystals are nanometric and ordered, these have to influence the vibrational states of the IR and Raman spectra.…”

“…Figure 1 shows that raw samples are constituted by ordered crystals; consequently, their peak widths are the result of elastic and inelastic diffraction contributions and are not due to a low crystalline quality (order) as have been previously pointed out. [18,25,26] It is clear that if the raw crystals are nanometric and ordered, these have to influence the vibrational states of the IR and Raman spectra. Figure 4a-d shows the IR bands located between 400 to 4,000 cm −1 for raw and calcinated samples and Sigma-Aldrich.…”

<p>Advanced Mg, Zn, Sr, Si Multi-Substituted Hydroxyapatites for Bone Regeneration</p>

“…A reduction of both the crystallite size and degree of crystallinity after Ca substitution by Mg was also reported. 42 Consequently, almost the same reduction in the crystallinity degree of pure HAP was observed for all multisubstituted HAPs, rather independent of the increasing amount of Sr in HAPc lattice. Therefore, it clearly appears that the Sr amount has a minor impact on the crystallinity of triple-substituted HAPc, in this range of concentration.…”

“…17 The effect of Mg, as a substituting element in HAP-Mg, on HAP characteristics is a subject of numerous different studies. 16,17,[37][38][39][40][41][42][43] Clearly, Mg is involved in skeletal metabolism and bone growth by increasing osteoblast cell activity and avoiding osteopenia and bone fragility, and thus playing an essential role in bone remodeling. 16,17,37 It was also suggested that Mg deficiency is linked to osteoporosis.…”

In vitro degradation behavior of as-cast Mg-3Zn-1Ca-0.5 Sr alloy

“…Although the potential difference of corrosion micro-galvanic α-Mg/Mg 17 Sr 2 is less than that of α-Mg/Ca 2 Mg 6 Zn 3 , α-Mg is etched as an anode in two pairs of micro-galvanic, so the role of α-Mg/Mg 17 Sr 2 and α-Mg/Ca 2 Mg 6 Zn 3 in the corrosion process is similar. The α-Mg corrosion near the second phase was faster, resulting in an increase in the concentration of Mg and Ca ions nearby and the formation of bulk HA with a smaller volume [26]. Part of the HA is formed by wrapping H 2 and becomes a chimney-like structure.…”