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Humidity sorption of lactose/sodium montmorillonite nanocomposites
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Pharmacy, Department of Pharmacy.
Department of Chemistry, Umeå University.
School of Pharmacy, University of East Anglia.
School of Pharmacy, University of East Anglia.
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

Understanding of water sorption is of high importance in materials science as water may change materials properties promoting degradation, relaxations, or recrystallization. In this study, we investigated the humidity sorption in co-spray-dried lactose/sodium montmorillonite nanocomposites with varying lactose loading with the aim to increase the knowledge of the water sorption in this type of materials. It was demonstrated that the intercalation of lactose in the Na‑MMT clay decreased hygroscopicity of the composite despite high water affinity of both materials. As the cations in interlayer space of montmorillonite play an essential role in water sorption in the clay, we gained the molecular level understanding of Na+ interactions with lactose molecules and clay surface in the nanocomposites with molecular dynamic simulations and 23Na solid-state NMR. In conclusion, we demonstrated that the decreased hygroscopicity of the materials can be explained by interactions of lactose with the Na+ and the clay surfaces in the MMT interlayer space of lactose/Na-MMT nanocomposites.

National Category
Materials Chemistry
Identifiers
URN: urn:nbn:se:uu:diva-300154OAI: oai:DiVA.org:uu-300154DiVA: diva2:950906
Available from: 2016-08-03 Created: 2016-08-03 Last updated: 2016-09-01
In thesis
1. Pharmaceutical Nanocomposites: Structure–Mobility–Functionality Relationships in the Amorphous State
Open this publication in new window or tab >>Pharmaceutical Nanocomposites: Structure–Mobility–Functionality Relationships in the Amorphous State
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Amorphous materials are found in pharmaceutical formulations both as excipients and active ingredients. Indeed, these formulations are becoming an essential strategy for incorporating drugs into well-performing solid dosage forms. However, there is an unmet need of better understanding of the microstructure and component interactions in amorphous formulations to be able to design materials with improved functionalities. The aim of this thesis is to give deepened knowledge about structure-mobility-functionality relationships in amorphous for-mulations by studying composites produced from sugars and filler particles. The structure, the mobility, and physical stability of the composite materials were studied using calorimetry, X-ray diffraction, microscopy, spectroscopy, and molecular dynamics simulations. Further, the moisture sorption of the composites was determined with dynamic vapor sorption. The compression mechanics of the composites was evaluated with compression analysis.

It was demonstrated that fillers change the overall properties of the amorphous material. Specifically, the physical stability of the composite was by far improved compared to the amorphous sugar alone. This effect was pronounced for formulations with 60 wt% filler content or more. Amorphous lactose that normally recrystallizes within a few minutes upon humidity exposure, could withstand recrystallization for several months at 60% RH in composites with 80 wt% cellulose nanocrystals (CNC) or sodium montmorillonite (Na-MMT). The increased physical stability of the amorphous sugars was related to intra-particle confinement in extra-particle voids formed by the fillers and to immobilization of the amorphous phase at the surface of the fillers. Also, the composite formation led to increased particle hardness for the lactose/CNC and the lactose/Na-MMT nanocomposites. The largest effect on particle hardness was seen with 40-60 wt% nanofiller and could be related to skeleton formation of the nanofillers within the composite particles. The hygroscopicity for the lactose/Na-MMT nanocomposites decreased as much as 47% compared to ideal simple mixtures of the neat components. The nanofillers did not influence the water sorption capacity in the amorphous domains; however, lactose (intercalated into Na-MMT) interacted with the sodium ions in the interlayer space which led to the lowered hygroscopicity of this phase.

The thesis advanced the knowledge of the microstructure of amorphous pharmaceutical com-posites and its relationship with pharmaceutical functionalities. It also presented new approaches for stabilizing the amorphous state by using fillers. The concept illustrated here might be used to understand similar phenomena of stabilization of amorphous formulations.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. 79 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Pharmacy, ISSN 1651-6192 ; 220
Keyword
amorphous, pharmaceutical composites, solid state, structure, molecular mobility, spray-drying, freeze-drying, moisture sorption, physical stability, compression
National Category
Materials Chemistry
Research subject
Pharmaceutical Science
Identifiers
urn:nbn:se:uu:diva-300159 (URN)978-91-554-9642-5 (ISBN)
External cooperation:
Public defence
2016-09-23, B21, BMC, Husargatan 3, Uppsala, 13:15 (English)
Opponent
Supervisors
Available from: 2016-08-31 Created: 2016-08-03 Last updated: 2016-09-05

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