The Mutual Incorporation of Mg2+ and CO32− into Hydroxyapatite: A DFT Study

Abstract

Hydroxyapatite (HA) with a stoichiometry composition of Ca10(PO4)6(OH)2 is widely applied for various biomedical issues, first of all for bone defect substitution, as a catalyst, and as an adsorbent for soil and water purification. The incorporation of foreign ions changes the acid–base relation, microstructure, porosity, and other properties of the HA materials. Here, we report the results of calculations of the density functional theory and analyze the possibility of two foreign ions, CO32− and Mg2+, to be co-localized in the HA structure. The Na+ was taken into account for charge balance preservation. The analysis revealed the favorable incorporation of CO32− and Mg2+ as a complex when they interact with each other. The energy gain over the sole ion incorporation was pronounced when CO32− occupied the A position and Mg2+ was in the Ca(2) position and amounted to -0.31 eV. In the most energy-favorable complex, the distance between Mg2+ and the O atom of carbonate ion decreased compared to Mg…O distances to the surrounding phosphate or hydroxide ions, and amounted to 1.98 Å. The theoretical calculations agree well with the experimental data reported earlier. Understating the structure–properties relationship in HA materials varying in terms of composition, stoichiometry, and morphology paves the way to rational designs of efficient bio-based catalytic systems.

Peculiarities of charge compensation in lithium-doped hydroxyapatite

“…The O–H bond where the H atom is located between the oxygen atoms of the shortening O⋯O pair becomes as long as 0.992 Å (compared to 0.979 Å in unperturbed anion channel of pure HA), but the O–H linkage of the inclined to Li + hydroxyl group becomes as short as 0.977 Å. These features of the geometry adjustment are strikingly different from those in the presence of other cations, where the oxygen atom of hydroxyl shifts from the anion channel axis towards the cation to shorten the distance to the foreigner ion [ 19 , [28] , [29] , [30] ].…”

Nutrient-Doped Hydroxyapatite: Structure, Synthesis and Properties

“…Another study by Laurencin et al reported the lattice distortion by Mg incorporation but mentioned falls in the lattice parameter (a) due to the substitution [88]. Further, Mg 2+ can substitute Ca (1) or Ca (2) sites and lead to a shortening distance between Mg and O [89]. In addition, Goldberg et al prepared Mg-HAP and reported that the substituting using Mg 2+ ions led to an increase in BET-specific surface area from 23.35 to 86.91 m 2 /g from 0 to 1% substitution.…”

On Antimicrobial Polymers: Development, Mechanism of Action, International Testing Procedures, and Applications

“…They do not fully dissolve in water but are slightly soluble at high pH levels (1.71 = mg L −1 at pH = 6.69) [ 136 ]. The ionic radius of Mg ++ is 72 pm [ 137 ]. They can disrupt cellular activity and release ROS.…”

“…They are sparingly soluble in water and able to form colloidal suspensions. The ionic radius of Mg ++ is 72 pm [ 137 ]. The mode of action involves activating ROS [ 141 ].…”