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The Effects of Additives on the Porosity and Stability of Amorphous Calcium Carbonate
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.ORCID iD: 0000-0002-5496-9664
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Nanotechnology and Functional Materials.ORCID iD: 0000-0002-4072-4324
2020 (English)In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 292, article id 109736Article in journal (Refereed) Published
Abstract [en]

Amorphous calcium carbonate (ACC) stabilized by various carboxylic additives was synthesized by incorporating the additives into an ACC suspension in methanol. The additives studied included polyacrylic acid, citric acid, adipic acid, 6-aminocaproic acid, 4-aminobutyric acid and hexanoic acid. The stabilized ACC samples (ACC-additives) exhibited similar characteristics to ACC alone. They appeared X-ray amorphous, contained characteristic infrared bands and had the same nanoparticle aggregated microstructure as ACC. The porosity of the ACC-additives was, however, markedly improved, with Brunauer-Emmett-Teller (BET) surface areas of up to ~640 m2/g. The BET surface area of ACC-citric acid was close to double that of a highly porous ACC sample. The structure and amount of the additive had a noticeable effect on the porosity of the ACC-additives. When the additive was adsorbed onto the surface of the ACC nanoparticles, their growth was restricted. The restricted growth reduced the size of the ACC nanoparticles, which increased the BET surface area of ACC. Finally, the long-term stability study revealed that the stability of all the ACC-additives was markedly enhanced when stored in ambient or semi-airtight conditions (in a closed falcon tube). In particular, ACC stabilized with adipic acid (ACC-AA-267) had excellent stability, remaining in an amorphous phase for more than one year under ambient conditions and retaining ~87% porosity for 48 weeks under semi-airtight conditions. The extremely high porosity and excellent long-term stability make these ACC-additives promising candidates for applications where porosity and stability are critical, such as those involving adsorption, bone regeneration or drug delivery.

Place, publisher, year, edition, pages
2020. Vol. 292, article id 109736
Keywords [en]
Amorphous calcium carbonate, Additives, Porosity, Stability
National Category
Nano Technology
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
URN: urn:nbn:se:uu:diva-391170DOI: 10.1016/j.micromeso.2019.109736ISI: 000498292200020OAI: oai:DiVA.org:uu-391170DiVA, id: diva2:1344275
Funder
Swedish Research Council, 2014-3929Swedish Research Council Formas, 2018-00651ÅForsk (Ångpanneföreningen's Foundation for Research and Development), 19-549Knut and Alice Wallenberg FoundationAvailable from: 2019-08-20 Created: 2019-08-20 Last updated: 2019-12-18Bibliographically approved
In thesis
1. Porous Amorphous Calcium Carbonate and Phosphate: Synthesis and Application
Open this publication in new window or tab >>Porous Amorphous Calcium Carbonate and Phosphate: Synthesis and Application
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The synthesis of porous amorphous calcium carbonate (ACC) and porous amorphous calcium phosphate (ACP) was developed in this thesis. Porous ACC with specific Brunauer–Emmett–Teller (BET) surface area of >350 m2/g was synthesized using a surfactant free approach. The high surface area of porous ACC was related to its nanostructure. Porous ACC was constructed with aggregated ACC nanoparticles that were less than 10 nm in diameter. The porosity and stability of porous ACC could be enhanced by introducing additives in the synthesis steps. The use of additives could also be used to control the crystallization of ACC to form vaterite particles with controllable morphologies. Porous ACC was tested as a drug carrier for two poorly soluble drugs (itraconazole and celecoxib). The porous ACC carrier was able to stabilize these drugs in their amorphous forms and enhance their release rate significantly when compared with the crystalline drug. Furthermore, porous ACC could also be used as a precursor/template for the synthesis of porous carbon. A porous carbon adsorbent with high uptake and high selectivity for greenhouse gases was produced. Porous ACP with a specific BET surface area of >400 m2/g was obtained by introducing phosphoric acid to the ACC suspension obtained during the synthesis of porous ACC. Similar to porous ACC, porous ACP was constructed of aggregated nanoparticles. ACP was found to be stable in ambient conditions for over 12 months and the stability could also be tailored by adjusting its composition. Porous ACP was cytocompatible and an effective drug carrier for alendronate - a bisphosphate drug for treatment of osteoporosis. The development of porous ACC and porous ACP as functional porous materials is summarized in this thesis.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2019. p. 71
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 1844
Keywords
amorphous calcium carbonate, amorphous calcium phosphate, stabilization, crystallization, porous material, drug delivery, gas adsorption
National Category
Nano Technology
Research subject
Engineering Science with specialization in Nanotechnology and Functional Materials
Identifiers
urn:nbn:se:uu:diva-391172 (URN)978-91-513-0727-5 (ISBN)
Public defence
2019-10-09, Häggsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 09:15 (English)
Opponent
Supervisors
Available from: 2019-09-18 Created: 2019-08-21 Last updated: 2019-10-15

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Sun, RuiStrømme, MariaCheung, Ocean

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