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Direct Probing of the Phosphate-Ion Distribution in Bioactive Silicate Glasses by Solid-State NMR: Evidence for Transitions between Random/Clustered Scenarios
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Physical Chemistry.
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Materials Chemistry.
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Physical Chemistry.
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2013 (English)In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 25, no 9, 1877-1885 p.Article in journal (Refereed) Published
Abstract [en]

By employing P-31 multiple-quantum coherence-based solid-state nuclear magnetic resonance spectroscopy, we present the first comprehensive experimental assessment of the nature of the orthophosphate ion distributions in silicate based bioactive glasses (BGs). Results are provided both from melt prepared BG and evaporation-induced self-assembly-derived mesoporous bioactive glass (MEBG) structures of distinct compositions. The phosphate species are randomly dispersed in melt-derived BGs (comprising 44-55 mol % SiO2) of the Na2O-CaO-SiO2-P2O5 system, whereas a Si-rich (86 mol % SiO2) and Ca-poor ordered MBG structure exhibits nanometer-sized amorphous calcium phosphate clusters, conservatively estimated to comprise at least nine orthophosphate groups. A Ca-richer MBG (58 mol % SiO2) reveals a less pronounced phosphate clustering. We rationalize the variable structural role of P in these amorphous biomatetials.

Place, publisher, year, edition, pages
2013. Vol. 25, no 9, 1877-1885 p.
Keyword [en]
bioactive glasses, phosphate distribution, calcium phosphate clusters, multiple quantum coherence, 45S5 Bioglass
National Category
Materials Chemistry Physical Chemistry
Research subject
Physical Chemistry
URN: urn:nbn:se:su:diva-92027DOI: 10.1021/cm400487aISI: 000319184600055OAI: diva2:637309
Swedish Research Council, 2009-7551, 2010-4943Knut and Alice Wallenberg Foundation


Available from: 2013-07-17 Created: 2013-07-15 Last updated: 2015-04-23Bibliographically approved
In thesis
1. Composition-Structure Correlations of Bioactive Glasses Explored by Multinuclear Solid-state NMR Spectroscopy
Open this publication in new window or tab >>Composition-Structure Correlations of Bioactive Glasses Explored by Multinuclear Solid-state NMR Spectroscopy
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This PhD thesis presents a study of structure-composition correlations of bioactive glasses (BGs) by employing solid-state Nuclear Magnetic Resonance (NMR) spectroscopy.

Silicate-based Na2O−CaO−SiO2−P2O5 BGs are utilized clinically and are extensively investigated for bone regeneration purposes. Once implanted in the human body, they facilitate bone regeneration by partially dissolving in the body fluids, followed by the formation of a biomimetic surface-layer of calcium hydroxy-carbonate apatite (HCA). Eventually, the implanted BG totally integrates with the bone. The bioactivity of melt-prepared BGs depends on their composition and structure, primarily on the phosphorus content and the average silicate-network connectivity (NC). We explored these composition-structure relationships for a set of BGs for which the NC and phosphorus contents were varied independently.

The short-range structural features of the glasses were explored using 29Si and 31P magic-angle-spinning (MAS) NMR spectroscopy. 31P MAS NMR revealed that the orthophosphate content is directly proportional to the total P content of the glass, with a linear correlation observed between the orthophosphate content and the silicate network connectivity. The bearings of the results for future BG design are discussed.

By using multiple-quantum coherence-based 31P NMR experiments, the spatial distribution of orthophosphate groups was probed in the melt prepared BGs, as well as in two mesoporous bioactive glasses prepared by an evaporation-induced self-assembly technique. The results evidence randomly distributed orthophosphate groups in the melt-prepared BGs, whereas the pore-walls of the mesoporous bioactive glasses constitute nanometer-sized clusters of calcium phosphate. The distribution of Na+ ions among the phosphate/silicate groups were studied by heteronuclear dipolar-based 23Na−31P NMR experiments, verifying that sodium is dispersed nearly randomly in the glasses.

The phosphorus and proton environments in biomimetically grown HCA were investigated by using 1H and 31P MAS NMR experiments. Our studies revealed that the biomimetic HCA shared many local structural features with synthetic and well-ordered hydroxy-apatite.

Place, publisher, year, edition, pages
Stockholm: Department of Materials and Environmental Chemistry (MMK), Stockholm University, 2015. 68 p.
bioactive glasses, glass structure, orthophosphate distribution, solid-state NMR, dipolar interactions, dipolar recoupling, multiple-quantum spin counting, READOR, REAPDOR
National Category
Natural Sciences
Research subject
Physical Chemistry
urn:nbn:se:su:diva-116232 (URN)978-91-7649-174-4 (ISBN)
Public defence
2015-06-03, Magnéli Hall, Arrhenius Laboratories, Svante Arrhenius väg 16 B, Stockholm, 13:00 (English)

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Accepted.

Available from: 2015-05-11 Created: 2015-04-15 Last updated: 2015-06-23Bibliographically approved

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