Mechanical preparation of nanocrystalline biocompatible single-phase Mn-doped A-type carbonated hydroxyapatite (A-cHAp): effect of Mn doping on microstructure

Abstract

Nanocrystalline biocompatible single-phase Mn-doped A-type carbonated hydroxyapatite (A-cHAp) powder has been synthesized by mechanical alloying of a stoichiometric mixture of CaCO3, CaHPO4·2H2O and MnO powder for 10 h at room temperature under open air. The A-type carbonation in HAp (substitution of CO3(2-) for OH(-)) is confirmed by FTIR analysis. Microstructure characterization in terms of lattice imperfections and phase quantification of ball milled samples are made by analyzing XRD patterns employing the Rietveld structure refinement method. Rietveld analysis of XRD patterns recorded from Mn-doped HAp samples has been used to locate Mn(2+) cations in HAp. The Ca2 vacancy site is found to be more favorable for Mn substitution. Microstructure characterization by HRTEM corroborates the findings of the X-ray analysis where the presence of a significant amount of amorphous phase of HAp analogous to indigenous bone mineral is clearly found. MTT assay shows sufficiently high percentage cell viability confirming the cytocompatibility of the sample.

Sic Parvis Magna: Manganese-Substituted Tricalcium Phosphate and Its Biophysical Properties

“…In general, the EPR spectra of Mn 2+ -containing compounds are sufficiently complex, especially in low-symmetry polycrystalline systems, as the averaging across all possible single crystal orientations and the overlap of signals from multiple possible sites lead to the broadening of the spectra. The obtained spectra showed typical Mn 2+ EPR spectral featureszero field splitting of the 6 S 5/2 ground state and hyperfine (HF) coupling to the 100% abundant 55 Mn nuclear spin I = 5/2. 40,49 No resonance signals were observed in the undoped sample.…”

“…Figure schematically shows the β-TCP structure accommodating Mn 2+ ions. Unlike in HA, where Ca 2+ ions occupy one of two possible sites, columnar (Ca(1)) and hexagonal (Ca(2)), there are up to five different Ca 2+ positions in the TCP structure and it is widely assumed that Mn 2+ favors the substitution at the Ca(5) site, with a geometry close to that of a regular octahedron. , In contrast, both Ca(1) and Ca(2) positions in the HA structure are filled by Mn 2+ even at very low concentrations of manganese, with the caveat that calcium vacancies are expected to be the first to be populated by Mn 2+ ions . However, as for HA, there is no reason not to assume that Mn 2+ could substitute Ca 2+ ions other than those residing in the Ca(5) position of the TCP structure (Figure ), such as, for example, Ca(4) and Ca(3) .…”

“…53,54 In contrast, both Ca(1) and Ca(2) positions in the HA structure are filled by Mn 2+ even at very low concentrations of manganese, with the caveat that calcium vacancies are expected to be the first to be populated by Mn 2+ ions. 55 However, as for HA, there is no reason not to assume that Mn 2+ could substitute Ca 2+ ions other than those residing in the Ca(5) position of the TCP structure (Figure 7), such as, for example, Ca(4) and Ca(3). 56 Although these results strongly suggest the accommodation of Mn 2+ ions at up to three different cation sites in the TCP lattice, the presented EPR data cannot unambiguously link the spectroscopic and structural parameters.…”

Small‐size effect on physicochemical properties of micronized fish bone during heating

“…The splitting peaks at 1,400 and 1,460 cm −1 suggested that carbon from the organics entered into the hydroxyapatite crystal (Fathi, Hanifi, & Mortazavi, ). Carbonate usually exists in hydroxyapatite of natural fish bones in the form of type‐B carbonate substitute ( was substituted by ) (Ivanova, Frank‐Kamenetskaya, Kol'tsov, & Ugolkov, ), which accounts for 2%–4% of mineral mass (Lala, Ghosh, Das, Kar, & Pradhan, ). Therefore, the disappeared peaks at around 1,452 cm −1 indicated the groups escaped from hydroxyapatite.…”

Atomistic mechanism of cadmium incorporation into hydroxyapatite

“…Ca1 and Ca2 are crystallographically inequivalent sites in HAp, and both have the potential for substitution of foreign ions. Although the preferred Ca site for different foreign ions is still under debate, more studies have suggested that Ca2 is the preferred site based on Rietveld analysis of XRD data and first principles calculations (Guerra-López et al, 2015;Lala et al, 2015;Luo et al, 2009;Terra et al, 2010). In this study, the local environment of Ca and Cd in This is the peer-reviewed, final accepted version for American Mineralogist, published by the Mineralogical Society of America.…”