ArticlePublisher preview available

Preparation, characterization and protein adsorption properties of nanostructured magnesium whitlockite

Authors:
Nadezhda Angelova at Sofia University "St. Kliment Ohridski"
Nadezhda Angelova
Savina Koleva at Sofia University "St. Kliment Ohridski"
Savina Koleva
Marco Kostadinov at Sofia University "St. Kliment Ohridski"
Marco Kostadinov
Georgi Yordanov at Sofia University "St. Kliment Ohridski"
Georgi Yordanov
Read publisher preview
Download citation
To read the full-text of this research, you can request a copy directly from the authors.

Abstract and Figures

This article presents the preparation and characterization of various calcium-magnesium phosphate suspensions with particular focus on nanostructured magnesium whitlockite as potential protein adsorbent. The phosphates were synthesized by precipitation from mixed Ca(II)/Mg(II) solutions with disodium hydrogen phosphate followed by thermal treatment at 95 or 115 °C for 1 or 3 h. Structural characterization was performed by means of transmission electron microscopy with elemental and electron diffraction analysis, X-ray powder diffraction and infrared spectroscopy. It was found that nanocrystalline magnesium whitlockite was obtained at initial Ca/Mg molar ratio from 65/35 up to 85/15. The crystallite sizes of magnesium whitlockite were estimated from X-ray diffraction and were found to vary from 5 to 45 nm depending on the heating temperature and time at constant Ca/Mg initial molar ratio of 75/25. The nanocrystalline magnesium whitlockite samples exhibited a relatively high protein adsorption capacity, which is an important prerequisite for applications in protein delivery.
Figures - available from: Journal of Materials Science
This content is subject to copyright. Terms and conditions apply.
A preview of this full-text is provided by Springer Nature.
Learn more
Content available from Journal of Materials Science
This content is subject to copyright. Terms and conditions apply.
CERAMICS
Preparation, characterization and protein adsorption
properties of nanostructured magnesium whitlockite
Nadezhda Angelova
1
, Savina Koleva
1
, Marco Kostadinov
1
, and Georgi Yordanov
1,
*
1
Faculty of Chemistry and Pharmacy, Sofia University St. Kliment Ohridski, 1164 Sofia, Bulgaria
Received: 27 September 2022
Accepted: 22 November 2022
Published online:
6 December 2022
ÓThe Author(s), under
exclusive licence to Springer
Science+Business Media, LLC,
part of Springer Nature 2022
ABSTRACT
This article presents the preparation and characterization of various calcium-
magnesium phosphate suspensions with particular focus on nanostructured
magnesium whitlockite as potential protein adsorbent. The phosphates were
synthesized by precipitation from mixed Ca(II)/Mg(II) solutions with disodium
hydrogen phosphate followed by thermal treatment at 95 or 115 °C for 1 or 3 h.
Structural characterization was performed by means of transmission electron
microscopy with elemental and electron diffraction analysis, X-ray powder
diffraction and infrared spectroscopy. It was found that nanocrystalline mag-
nesium whitlockite was obtained at initial Ca/Mg molar ratio from 65/35 up to
85/15. The crystallite sizes of magnesium whitlockite were estimated from X-ray
diffraction and were found to vary from 5 to 45 nm depending on the heating
temperature and time at constant Ca/Mg initial molar ratio of 75/25. The
nanocrystalline magnesium whitlockite samples exhibited a relatively high
protein adsorption capacity, which is an important prerequisite for applications
in protein delivery.
Introduction
As essential elements, calcium and magnesium are
involved in a variety of physiological processes [1].
Among the various calcium and magnesium-based
materials, calcium and magnesium phosphates have
attracted an increasing interest in biomedical fields,
mainly as materials for bone repair, drug/protein
delivery systems and immunological adjuvants [2–6].
Calcium phosphate is a compound naturally present
in the organism (as hydroxyapatite in bone and teeth)
and already used in human vaccination as an effec-
tive immunological adjuvant [4,5]. On the other
hand, magnesium phosphate nanoparticles have
been demonstrated as effective non-viral vectors for
DNA delivery in DNA vaccines [6–8]. One of the
mechanisms of immunological adjuvants involves
delivery of the antigen (usually a protein) to the
antigen-presenting cells [9] (macrophages, dendritic
Handling Editor: M. Grant Norton.
Address correspondence to E-mail: g.g.yordanov@gmail.com
https://doi.org/10.1007/s10853-022-08011-z
J Mater Sci (2022) 57:21571–21582
Ceramics
Content courtesy of Springer Nature, terms of use apply. Rights reserved.
ResearchGate has not been able to resolve any citations for this publication.
The Potential of Calcium Phosphate Nanoparticles as Adjuvants and Vaccine Delivery Vehicles
Article
Full-text available
  • Dec 2021
Vaccination is one of the most efficacious and cost-effective ways to protect people from infectious diseases and potentially cancer. The shift in vaccine design from disrupted whole pathogens to subunit antigens has brought attention on to vaccine delivery materials. For the last two decades, nanotechnology-based vaccines have attracted considerable attention as delivery vehicles and adjuvants to enhance immunogenicity, exemplified with the current COVID vaccines. The nanoparticle vaccines display unique features in protecting antigens from degradation, controlled antigen release and longer persisting immune response. Due to their size, shape and surface charge, they can be outstanding adjuvants to achieve various immunological effects. With the safety and biodegradable benefit of calcium phosphate nanoparticles (CaP NPs), they are an efficient carrier for vaccine design and adjuvants. Several research groups have studied CaP NPs in the field of vaccination with great advances. Although there are several reports on the overview of CaP NPs, they are limited to the application in biomedicine, drug delivery, bone regeneration and the methodologies of CaP NPs synthesis. Hence, we summarised the basic properties of CaP NPs and the recent vaccine development of CaP NPs in this review.
View
Magnesium whitlockite – omnipresent in pathological mineralisation of soft tissues but not a significant inorganic constituent of bone
Article
Full-text available
  • Feb 2021
  • ACTA BIOMATER
Whitlockite is a calcium phosphate that was first identified in minerals collected from the Palermo Quarry, New Hampshire. The terms magnesium whitlockite [Mg-whitlockite; Ca18Mg2(HPO4)2(PO4)12] and beta-tricalcium phosphate [β-TCP; β-Ca3(PO4)2] are often used interchangeably since Mg-whitlockite is not easily distinguished from β-Ca3(PO4)2 by powder X-ray diffraction although their crystalline structures differ significantly. Being both osteoconductive and bioresorbable, Mg-whitlockite is pursued as a synthetic bone graft substitute. In recent years, advances in development of synthetic Mg-whitlockite have been accompanied by claims that Mg-whitlockite is the second most abundant inorganic constituent of bone, occupying as much as 20–35 wt% of the inorganic fraction. To find evidence in support of this notion, this review presents an exhaustive summary of Mg-whitlockite identification in biological tissues. Mg-whitlockite is mainly found in association with pathological mineralisation of various soft tissues and dental calculus, and occasionally with enamel and dentine. With the exception of high-temperature treated bone from certain species of fish and tumoural calcified deposits around interphalangeal and metacarpal joints, and rhomboidal Mg-whitlockite crystals in post-apoptotic osteocyte lacunae in human alveolar bone, this unusual mineral has never been detected in the extracellular matrix of bone. Characterisation techniques capable of unequivocally distinguishing between different calcium phosphate phases, such as high-resolution imaging, crystallography, and/or spectroscopy have exclusively identified bone mineral as poorly crystalline, ion-substituted, carbonated apatite. The idea that Mg-whitlockite is a significant constituent of bone mineral remains unsubstantiated. Contrary to claims that such biomaterials represent a bioinspired/biomimetic approach to bone repair, Mg-whitlockite remains, exclusively, a pathological biomineral.
View
Biological and Medical Applications of Calcium Phosphate Nanoparticles
Article
Full-text available
Calcium phosphate nanoparticles have a high biocompatibility and biodegradability due to their chemical similarity to human hard tissue, for example, bone and teeth. They can be used as efficient carriers for different kinds of biomolecules such as nucleic acids, proteins, peptides, antibodies, or drugs, which alone are not able to enter cells where their biological effect is required. They can be loaded with cargo molecules by incorporating them, unlike solid nanoparticles, and also by surface functionalization. This offers protection, for example, against nucleases, and the possibility for cell targeting. If such nanoparticles are functionalized with fluorescing dyes, they can be applied for imaging in vitro and in vivo. Synthesis, functionalization and cell uptake mechanisms of calcium phosphate nanoparticles are discussed together with applications in transfection, gene silencing, imaging, immunization, and bone substitution. Biodistribution data of calcium phosphate nanoparticles in vivo are reviewed.
View
Synthesis, Characterization and Process Optimization of Bone Whitlockite
Article
Full-text available
  • Sep 2020
Whitlockite, being the second most abundant bio-mineral in living bone, finds huge applications in tissue regeneration and implants and its synthesis into its pure form has remained a challenge. Although precipitation of whitlockite phase has been reported recently in many publications, effects of various parameters to control such phase as well as conditions for the bulk preparation of this extremely important bio-mineral have not been investigated so far. In this work, we report the precipitation of pure whitlockite phase using common precursors. As reported in the literature, whitlockite is stable in a narrow pH range, therefore; optimization of pH for the stabilization of whitlockite phase has been investigated. Additionally, in order to narrow down the optimum conditions for the whitlockite precipitation, effect of temperature and heating conditions has also been studied. The obtained solids were characterized using powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). From PXRD analysis, it was observed that heating the precursor's mixture at 100 °C with subsequent aging at the optimized pH resulted in the precipitation of pure whitlockite phase. These results were further confirmed by TGA, SEM and Raman spectroscopy analysis and it was confirmed that the conditions reported here favor whitlockite precipitation without formation of any secondary phase. These reaction conditions were further confirmed by changing all the parameters like aging, heating time, feed rate of precursors one by one. From PXRD analysis of these samples, it was concluded that not only pH but temperature, heating time, aging time and feed rate effect simultaneously on the precipitation of pure whitlockite phase and a subtle change in any of these parameters could lead to the formation of undesired stable secondary calcium phosphate phases.
View
View
Biodegradable magnesium phosphates in biomedical applications
Article
  • Mar 2022
As an essential element, magnesium is involved in a variety of physiological processes. Magnesium is the second most abundant cation in cells and the fourth most abundant cation in living organisms. Magnesium-based biomaterials are considered to be biocompatible and biodegradable, and they are promising for application in biomedicine. Among them, magnesium phosphates have attracted increasing interest in biomedical fields in recent years, because both magnesium and phosphorus are common elements in the human body. Magnesium phosphates exhibit many similar characteristics, such as excellent biocompatibility and pH-responsive degradability, to calcium phosphates that are widely applied in biomedicine. Magnesium phosphates are used in nanomedicine in the form of monodisperse particles, or used in tissue engineering in the form of cements, ceramics, scaffolds, coatings and so on. This review focuses on the state-of-the-art progress made in magnesium phosphate-based biomaterials and their biomedical applications, including nanostructured magnesium phosphates and magnesium phosphate-based cements, ceramics, scaffolds, coatings and so on. Finally, the challenges and future research directions of magnesium phosphate-based biomaterials are also explored.
View
Synthesis and formation mechanism of bone mineral, whitlockite nanocrystals in tri-solvent system
Article
  • Feb 2020
Whitlockite (WH, Ca18Mg2(HPO4)2(PO4)12) is the second most abundant bone mineral and has attracted attention as one of the novel bone regenerative materials. It has proven to enhance growth and promote osteogenesis of stem cells. However, investigating the mechanism of formation of pure phase WH nanocrystals remains a challenge. In this study, we introduced an interesting synthesis approach of WH nanocrystals using a tri-solvent system for the solid-liquid-solution (SLS) process. The ratio of precursor and reaction solvent composition was optimized to generate WH nanocrystals with tunable size, morphology (nanoplates, nanospheres), and surface properties (hydrophobic, hydrophilic), which is impossible to achieve using the traditional precipitation method. Molecular dynamics (MD) simulations revealed that the growth direction of nanoplates is highly related to the surfactant and its binding affinity. Finite element method (FEM) simulations elucidated that the ratio of ethanol/water plays an important role in defining the crystallinity and morphology of WH. In this study, we demonstrated that the cell proliferation of human bone marrow-derived mesenchymal stem cells (hBMSCs) is enhanced upon treatment with WH. The results of quantitative real-time polymerase chain reaction (qPCR) revealed that WH can positively accelerate the osteogenic differentiation in hBMSCs. The as-synthesized WH has a great potential in the future to be used in osteogenic tissue engineering. This study opens a new horizon for the synthesis and application of WH.
View
Iron(III) and aluminium(III) based mixed nanostructured hydroxyphosphates as potential vaccine adjuvants: Preparation and physicochemical characterization
Article
  • Sep 2017
  • COLLOID SURFACE A
Adjuvants are substances that, when combined with an antigen in a vaccine formulation, potentiate the immune response against that antigen. Aluminium hydroxyphosphate is among the currently used adjuvants in vaccines, while studies on its iron analogue, ferric hydroxyphosphate, are quite limited. In this article we report on the preparation and physicochemical characterization of novel nanostructured iron and aluminium based mixed hydroxyphosphates as potential vaccine adjuvants, prepared by controlled co-precipitation from mixed solutions of Fe(III) and Al(III) chlorides with sodium phosphate and sterilized by autoclaving. The obtained hydroxyphosphates consisted of a network of platy nanoparticles (20–40 nm in size), which aggregated in aqueous medium to form secondary micron-sized particles. The obtained nanostructured hydroxyphosphates were characterized by energy dispersive X-ray spectroscopy for elemental composition, X-ray powder diffraction, infrared spectroscopy, zeta-potential measurements for determination of isoelectric point, protein adsorption, and dissolution rate in sodium citrate solution.
View
Hydrothermal growth of whitlockite coating on β-tricalcium phosphate surfaces for enhancing bone repair potential
Article
  • Jul 2017
  • J MATER SCI TECHNOL
In this study, we developed a simple approach for the controllable growth of whitlockite (WH) on a β-tricalcium phosphate surface and investigated its cell viability via CCK-8, its live-dead staining and its alkaline phosphatase activity. Herein, WH with controllable morphologies was prepared by regulating the hydrothermal reaction conditions. The results of scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy indicated that pure hexagonal plates of WH were prepared successfully. In vitro cell experiments showed that WH possessed excellent biocompatibility and effectively promoted the adhesion and proliferation of mouse bone mesenchymal stem cells. The osteogenesis of the WH was also enhanced. The obtained WH was expected to be utilized for promising applications as implantable block materials for bone repair.
View
Biomimetic whitlockite inorganic nanoparticles-mediated in situ remodeling and rapid bone regeneration
Article
  • Jan 2017
Bone remodeling process relies on complex signaling pathway between osteoblasts and osteoclasts and control mechanisms to achieve homeostasis of their growth and differentiation. Despite previous achievements in understanding complicated signaling pathways between cells and bone extracellular matrices during bone remodeling process, a role of local ionic concentration remains to be elucidated. Here, we demonstrate that synthetic whitlockite (WH: Ca18Mg2(HPO4)2(PO4)12) nanoparticles can recapitulate early-stage of bone regeneration through stimulating osteogenic differentiation, prohibiting osteoclastic activity, and transforming into mechanically enhanced hydroxyapatite (HAP)-neo bone tissues by continuous supply of PO4³⁻ and Mg²⁺ under physiological conditions. In addition, based on their structural analysis, the dynamic phase transformation from WH into HAP contributed as a key factor for rapid bone regeneration with denser hierarchical neo-bone structure. Our findings suggest a groundbreaking concept of ‘living bone minerals’ that actively communicate with the surrounding system to induce self-healing, while previous notions about bone minerals have been limited to passive products of cellular mineralization.
View