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Toward a Rational Design of Bioactive Glasses with Optimal Structural Features: Composition-Structure Correlations Unveiled by Solid-State NMR and MD Simulations
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), Physical Chemistry.
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK), Physical Chemistry.
2014 (English)In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 118, no 3, 833-844 p.Article in journal (Refereed) Published
Abstract [en]

The physiological responses of silicate-based bioactive glasses (BGs) are known to depend critically on both the P content (np) of the glass and its silicate network connectivity ((N) over bar (SI)(BO)). However, while the bioactivity generally displays a nonmonotonic dependence on np itself, recent work suggest that it is merely the net orthophosphate content that directly links to the bioactivity. We exploit molecular dynamics (MD) simulations combined with P-31 and Si-29 solid-state nuclear magnetic resonance (NMR) spectroscopy to explore the quantitative relationships between (N) over bar (SI)(BO), npand the silicate and phosphate speciations in a series of Na2O-CaO-SiO2-P2O5 glasses spanning 2.1 <=(N) over bar (SI)(BO) <= 2.9 and variable P2O5 contents up to 6.0 mol %. The fractional population of the orthophosphate groups remains independent of np at a fixed (N) over bar (SI)(BO)-value, but is reduced slightly as (N) over bar (SI)(BO) increases. Nevertheless, P remains predominantly as readily released orthophosphate ions, whose content may be altered essentially independently of the network connectivity, thereby offering a route to optimize the glass bioactivity. We discuss the observed composition-structure links in relation to known composition-bioactivity correlations, and define how Na2O-CaO-SiO2-P2O5 compositions exhibiting an optimal bioactivity can be designed by simultaneously altering three key parameters: the silicate network connectivity, the (ortho)phosphate content, and the n(Na)/n(ca) molar ratio.

Place, publisher, year, edition, pages
2014. Vol. 118, no 3, 833-844 p.
National Category
Physical Chemistry
Research subject
Physical Chemistry
Identifiers
URN: urn:nbn:se:su:diva-101004DOI: 10.1021/jp409652kISI: 000330252700020OAI: oai:DiVA.org:su-101004DiVA: diva2:699701
Note

AuthorCount:4;

Available from: 2014-02-28 Created: 2014-02-21 Last updated: 2017-12-05Bibliographically 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.
Keyword
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
Identifiers
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)
Opponent
Supervisors
Note

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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