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In-situ Synchrotron X-ray Diffraction Analysis of the Setting Process of Brushite Cement: Reaction and Crystal Growth
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. (Materials in Medicine Group)ORCID iD: 0000-0001-6830-1633
Max IV Laboratory, Lund University.
Max IV Laboratory, Lund University.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials. (Nanotechnology and Functional Materials)
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2017 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 9, no 41, p. 36392-36399Article in journal (Refereed) Published
Abstract [en]

Brushite cements are fast self-setting materials that can be used as bone substitute materials. Although tracing their fast setting process is a challenge, it is important for the understanding of the same, which in turn is important for the material’s further development and use in the clinics. In this study, the setting rate, phase formation, and crystal growth of brushite cements were quantitatively studied by in situ synchrotron powder X-ray diffraction (SXRD) on a time scale of seconds. The influence of reactant ratios and a retardant (citric acid) on the setting reaction were analyzed. To complement the in situ investigations, scanning electron microscopy was carried out for ex situ morphological evolution of crystals. The initial reaction followed a four-step process, including a fast nucleation induction period, nucleation, crystal growth, and completion of the setting. The brushite crystal size grew up to the micro scale within 1 min, and the brushite content increased linearly after the nucleation until all monocalcium phosphate monohydrate (MCPM; Ca(H2PO4)2·H2O) had dissolved within minutes, followed by a slow increase until the end of the monitoring. By adjusting the MCPM to the β-tricalcium phosphate (β-TCP, β-Ca3(PO4)2) ratio in the starting powders, the brushite/monetite ratio in the cements could be modified. In the presence of citric acid, the formation of brushite nuclei was not significantly retarded, whereas the increase in brushite content and the growth of crystal size were effectively hindered. The amount of monetite also increased by adding citric acid. This is the first time that the brushite setting process has been characterized in the first seconds and minutes of the reaction by SXRD.

Place, publisher, year, edition, pages
2017. Vol. 9, no 41, p. 36392-36399
Keywords [en]
synchrotron X-ray diffraction, setting reaction process, brushite cement, crystal size, citric acid, MCPM/β-TCP ratio
National Category
Engineering and Technology Medical Materials Biomaterials Science
Research subject
Engineering Science with specialization in Materials Science
Identifiers
URN: urn:nbn:se:uu:diva-330146DOI: 10.1021/acsami.7b10159ISI: 000413503700092OAI: oai:DiVA.org:uu-330146DiVA, id: diva2:1144626
Available from: 2017-09-26 Created: 2017-09-26 Last updated: 2018-08-10Bibliographically approved
In thesis
1. Calcium Phosphate Based Biomaterials for Bone Augmentation
Open this publication in new window or tab >>Calcium Phosphate Based Biomaterials for Bone Augmentation
2018 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Basic (apatite-based) calcium phosphate cements (CPCs), and acidic (brushite and monetite-based) CPCs are used as bone replacement materials because of their bioactivity, mouldability and ability to harden in place. However, their application is limited by their inherent brittleness and difficulties related to their handling. The current thesis aimed to provide solutions to these limitations.

To assess the baseline, the mechanical properties of two promising experimental and two commercially available apatite and brushite cements were investigated. The two experimental CPCs exhibited significantly higher mechanical strengths than the two commercially available ones, warranting further advancement of the former towards clinical use.

The setting reaction of brushite cements was, for the first time, quantitatively studied in the first seconds and minutes, using synchrotron X-ray diffraction. The reaction was found to include a fast nucleation induction period (<9 s), nucleation (<18 s), brushite content increase and setting completion. The effect of the commonly used retardant citric acid – which usually also gives stronger brushite cements - was also evaluated, providing important information for further cement development.  

To overcome complicated usage and short shelf life of acidic CPCs, a ready-to-use acidic CPC was developed by mixing a monocalcium phosphate monohydrate (MCPM) paste and a β-tricalcium phosphate (β-TCP) paste with suitable amounts of citric acid. The CPC showed adequate shelf life, good cohesion and mechanical performance.

To mitigate against the brittle behavior of CPCs, i) poly(vinyl alcohol) fibres were used to reinforce apatite cements, significantly improving the apatite matrix’s toughness and resistance to cracking; ii) injectable, ready-to-use organic-inorganic composites with partly elastomeric compression behavior were designed based on silk fibroin hydrogels and acidic calcium phosphates, and their ability for antibiotic drug delivery was assessed. 

In summary, insights into the functional properties of currently available CPCs as well as the setting process of brushite cements were gained and several new calcium phosphate-based formulations were developed to overcome some of the drawbacks of traditional CPCs. Further studies, in particular of the biological response, are needed to verify the potential of the developed materials for future use in the clinical setting. 

 

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2018. p. 55
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1700
Keywords
bone substitute materials, calcium phosphate cements, apatite, brushite, monetite, setting mechanism, premixed, fibre reinforcement, composite, silk fibroin, mechanical properties
National Category
Ceramics Composite Science and Engineering
Research subject
Engineering Science with specialization in Materials Science
Identifiers
urn:nbn:se:uu:diva-356982 (URN)978-91-513-0399-4 (ISBN)
Public defence
2018-09-28, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2018-09-05 Created: 2018-08-10 Last updated: 2018-09-10

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Luo, JunYang, JiaojiaoPersson, CeciliaEngqvist, HåkanXia, Wei

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