| 11. |
- Bai Palmkron, Shuai, et al.
(författare)
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Quantification of structures in freeze-dried materials using X-ray microtomography
- 2023
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Ingår i: Colloids and Surfaces A. - : Elsevier BV. - 0927-7757 .- 1873-4359. ; 658
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Tidskriftsartikel (refereegranskat)abstract
- The structure of a freeze-dried material is essential for its ability to preserve and protect biologics such as proteins, cells and other sensitive structures. The structure of a typical freeze-dried matrix can be described as pores surrounded by thin walls where the walls are the encapsulating material (for e.g. cells). The objective of this investigation is to evaluate X-ray microtomography (µCT) as a characterization method to quantifying the matrix of a freeze dried material, and compare it to scanning electron microscopy (SEM). The material consists of maltodextrin, freeze-dried below or above the glass transition temperature of the maximal freeze concentration (Tg′) and after applying annealing. The SEM images have high resolution and provide an excellent view of the sample. However, it is challenging to perform any image analysis and to ensure that a representative section is presented. The µCT images provide a rather uniform contrast between material and void, allowing for a simple grey-level thresholding when separating structure from the background. A robust image analysis procedure allows the results extracted from a representative sample volume to be evaluated. Further image analysis has been focused on understanding the thickness of the encapsulating structures by estimations of volume-weighted averages of inscribed spheres within the walls. The results show two types of structures: A large pore structure of around 20–100 µm separated by thin walls around 2–3 µm thick, and a finer structure consisting of smaller pockets of air (< 10 µm) packed in a honeycomb like structure. The structures of the samples dried below and above Tg′ have smaller and thinner structures, while material dried after annealing has larger and thicker structures. The structures display comparably small differences between the different drying protocols despite the quite different drying conditions.
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| 12. |
- Bogdanova, Ekaterina, et al.
(författare)
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Hydration enthalpies of amorphous sucrose, trehalose and maltodextrins and their relationship with heat capacities.
- 2021
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 23:26, s. 14433-14448
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Tidskriftsartikel (refereegranskat)abstract
- The mechanisms of glass transitions and the behavior of small solute molecules in a glassy matrix are some of the most important topics of modern thermodynamics. Water plays an important role in the physical and chemical stability of lyophilized biologics formulations, in which glassy carbohydrates act as cryoprotectants and stabilizers. In this study, sorption calorimetry was used for simultaneous measurements of water activity and the enthalpy of water sorption by amorphous sucrose, trehalose and maltodextrins. Moreover, the heat capacity of these carbohydrates in mixtures with water was measured by DSC in a broad range of water contents. The hydration enthalpies of glassy sucrose, trehalose and maltodextrins are exothermic, and the enthalpy change of water-induced isothermal glass transitions is higher for small molecules. The partial molar enthalpy of mixing of water in slow experiments is about -18 kJ mol-1, but less exothermic in the case of small molecules at fast hydration scan rates. By measuring the heat capacities of disaccharides and maltodextrins as a function of water content, we separated the contributions of carbohydrates and water to the total heat capacities of the mixtures. The combination of these data allowed testing of thermodynamic models describing the hydration-induced glass transitions. The heat capacity changes calculated by the fitting of the hydration enthalpy data for disaccharides are in good agreement with the heat capacity data obtained by DSC, while for maltodextrins, the effect of sub-Tg transitions should be taken into account. Combining the data obtained by different techniques, we found a distinct difference in the behavior of water in glassy polymers compared to that in glassy disaccharides. By understanding the behavior of water in glassy carbohydrates, these results can be used to improve the design of freeze-dried formulations of proteins and probiotics.
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| 13. |
- Bogdanova, Ekaterina, et al.
(författare)
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Influence of Cooling Rate on Ice Crystallization and Melting in Sucrose-Water System
- 2022
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Ingår i: Journal of Pharmaceutical Sciences. - : Elsevier B.V.. - 0022-3549 .- 1520-6017. ; 111:7, s. 2030-2037
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Tidskriftsartikel (refereegranskat)abstract
- The ice crystallization and melting in systems where the equilibrium state is difficult to reach is one of the growing areas in pharmaceutical freeze-drying research. The quality of the final freeze-dried product depends on the parameters of the cooling step, which affect the ice nucleation and growth. In this paper, we present a DSC study of ice crystallization and melting in a sucrose-water system. Using two different types of thermal cycles, we examine the influence of cooling and heating rates on the thermal behavior of sucrose-water solutions with water contents between 50 and 100 wt%. The DSC results show that low cooling rates provide crystallization at higher temperatures and lead to lower amount of non-freezing water. Consequently, the glass transition and ice melting properties observed upon heating depend on the cooling conditions in the preceding step. Based on the experimental results, we investigate the reasons for the existence of the two steps on DSC heating curves in sucrose-water systems: the glass transition step and the onset of ice melting. We show that diffusion of water can be the limiting factor for ice growth and melting in the sucrose-water system when the amorphous phase is in a liquid state. In particular, when the diffusion coefficient drops below 10−14 m2/sec, the ice crystals growth or melting becomes strongly suppressed even above the glass transition temperature. Understanding the diffusion limitations in the sucrose-water system can be used for the optimization of the freeze-drying protocols for proteins and probiotics. © 2022 The Authors
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| 14. |
- Bogdanova, Ekaterina, et al.
(författare)
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Lysozyme-Sucrose Interactions in the Solid State : Glass Transition, Denaturation, and the Effect of Residual Water
- 2023
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Ingår i: Molecular Pharmaceutics. - : American Chemical Society. - 1543-8384 .- 1543-8392. ; 20:9, s. 4664-
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Tidskriftsartikel (refereegranskat)abstract
- The freeze-drying of proteins, along with excipients, offers a solution for increasing the shelf-life of protein pharmaceuticals. Using differential scanning calorimetry, thermogravimetric analysis, sorption calorimetry, and synchrotron small-angle X-ray scattering (SAXS), we have characterized the properties at low (re)hydration levels of the protein lysozyme, which was freeze-dried together with the excipient sucrose. We observe that the residual moisture content in these samples increases with the addition of lysozyme. This results from an increase in equilibrium water content with lysozyme concentration at constant water activity. Furthermore, we also observed an increase in the glass transition temperature (Tg) of the mixtures with increasing lysozyme concentration. Analysis of the heat capacity step of the mixtures indicates that lysozyme does not participate in the glass transition of the sucrose matrix; as a result, the observed increase in the Tg of the mixtures is the consequence of the confinement of the amorphous sucrose domains in the interstitial space between the lysozyme molecules. Sorption calorimetry experiments demonstrate that the hydration behavior of this formulation is similar to that of the pure amorphous sucrose, while the presence of lysozyme only shifts the sucrose transitions. SAXS analysis of amorphous lysozyme-sucrose mixtures and unfolding of lysozyme in this environment show that prior to unfolding, the size and shape of lysozyme in a solid sucrose matrix are consistent with its native state in an aqueous solution. The results obtained from our study will provide a better understanding of the low hydration behavior of protein-excipient mixtures and support the improved formulation of biologics. © 2023 The Authors.
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| 15. |
- Boge, Lukas, et al.
(författare)
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Freeze-dried and re-hydrated liquid crystalline nanoparticles stabilized with disaccharides for drug-delivery of the plectasin derivative AP114 antimicrobial peptide
- 2018
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Ingår i: Journal of Colloid and Interface Science. - : Elsevier BV. - 0021-9797 .- 1095-7103. ; 522, s. 126-135
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Tidskriftsartikel (refereegranskat)abstract
- Liquid crystalline nanoparticles (LCNPs), e.g. cubosomes and hexosomes, are receiving more and more attraction as drug delivery vehicles. Dry powder formulation that forms LCNPs upon hydration can be advantageous to make new routes of administration accessible. In this work, we investigate use of three disaccharides (lactose, trehalose and sucrose) as protective matrices for glycerol monooleate based LCNP forming powders produced by freeze-drying. Phase behavior, particle size and size distributions at the different preparation steps were monitored by small angle x-ray scattering (SAXS) and dynamic light scattering (DLS). Particle appearance was imaged by cryogenic transmission electron microscopy (cryo-TEM). Moreover, the therapeutic relevant antimicrobial peptide AP114 (plectasin derivative) was incorporated in the formulations. Peptide encapsulation and release as well as in vitro antibacterial effect were investigated. Results showed that all freeze-dried powders did form particles with liquid crystalline structure upon hydration. However, a phase transition from the bicontinuous cubic Pn3m to the reversed hexagonal was observed, as a consequence of sugar addition and the freeze-drying procedure. Data indicates that trehalose is the preferred choice of lyo-protectant in order to maintain a mono-modal particle size distribution. In addition, antimicrobial activity of AP114-containing formulations was found to be highest for the formulation containing trehalose. The release kinetics of AP114 from the nanoparticles was strongly affected by the dimensions of the hexagonal phase. Larger dimension of the hexagonal phase, significantly improved the release of AP114 and antimicrobial activity of the formulation.
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| 16. |
- Both, E M, et al.
(författare)
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Morphology development during single droplet drying of mixed component formulations and milk
- 2018
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Ingår i: Food Research International. - : Elsevier BV. - 0963-9969 .- 1873-7145. ; 109, s. 448-454
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Tidskriftsartikel (refereegranskat)abstract
- We report on the influence of selected components and their mixtures on the development of the morphology during drying of single droplets and extend the results to the morphology of whole milk powder particles. Sessile single droplet drying and acoustic levitation methods were employed to study single droplet drying. The influence of carbohydrates (lactose and maltodextrin DE12) and proteins (micellar casein or whey protein) on morphology development is very different, since upon concentration protein systems will jam and undergo a colloidal glass transition, whereas carbohydrate systems will gradually increase in viscosity as a consequence of the concentration. Whey protein gives relatively rigid shells due to jamming of the "hard sphere" proteins, while casein micelles behave as "soft spheres" that can deform after jamming, which gives flexibility to the shell during drying. The influence of the carbohydrates on the final morphology was found much larger than the influence of the proteins. Caseins influenced morphology only in mixtures with lactose at higher concentrations due to its high voluminosity. Similar observations were done for whole milk, where fat appeared to have no influence. With maltodextrin the influence of the casein was again observed in the shape and smoothness of wrinkles. Both sessile and levitated droplet drying methods provide a similar and consistent view on morphology development.
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| 17. |
- Cappelletto, Elia, et al.
(författare)
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Impact of Post Manufacturing Handling of Protein-Based Biologic Drugs on Product Quality and User Centricity
- 2024
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Ingår i: Journal of Pharmaceutical Sciences. - : Elsevier. - 0022-3549 .- 1520-6017.
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Tidskriftsartikel (refereegranskat)abstract
- This article evaluates the current gaps around the impact of post-manufacturing processes on the product qualities of protein-based biologics, with a focus on user centricity. It includes the evaluation of the regulatory guidance available, describes a collection of scientific literature and case studies to showcase the impact of post-manufacturing stresses on product and dosing solution quality. It also outlines the complexity of clinical handling and the need for communication, and alignment between drug providers, healthcare professionals, users, and patients. Regulatory agencies provide clear expectations for drug manufacturing processes, however, guidance supporting post-product manufacturing handling is less defined and often misaligned. This is problematic as the pharmaceutical products experience numerous stresses and processes which can potentially impact drug quality, safety and efficacy. This article aims to stimulate discussion amongst pharmaceutical developers, health care providers, device manufacturers, and public researchers to improve these processes. Patients and caregivers' awareness can be achieved by providing relevant educational material on pharmaceutical product handling.
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| 18. |
- Dahlberg, Carina, 1980-
(författare)
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Drugs and polymers in dissolving solid dispersions : NMR imaging and spectroscopy
- 2010
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The number of poorly water-soluble drug substances in the pharmaceutical pipeline is increasing, and thereby also the need to design effective drug delivery systems providing high bioavailability. One favourable formulation approach is preparation of solid dispersions, where dispersing a poorly water-soluble drug in a water-soluble polymer matrix improves the dissolution behaviour and the bioavailability of the drug. However, in order to take full advantage of such formulations the impact of material properties on their performance needs to be investigated. An experimental toolbox has been designed, and applied, for analysing the processes which govern the behaviour of solid pharmaceutical formulations in general, and that of solid dispersions in particular. For the purpose of monitoring multifaceted phenomena in situ during tablet dissolution, nuclear magnetic resonance (NMR) spectroscopy and NMR imaging are superior to many other techniques, both on macroscopic and molecular levels. The versatility of NMR with its isotope and chemical selectivity allows one to follow the influence of the original tablet properties on polymer mobilisation, drug migration and water penetration selectively. Mapping these processes on relevant time scales in dissolving tablets highlighted the gel layer inhomogeneity below the originally dry tablet surface as a key factor for drug release kinetics. Furthermore, NMR relaxometry has been shown to provide novel information about the particle size of the drug and its recrystallisation behaviour within swelling solid dispersions. The NMR experiments have been complemented and supported by investigation of the crystalline state, the powder morphology and the surface composition of the dry solid dispersions. These experiments have been performed by X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), powder X-ray diffraction (pXRD), differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and dynamic contact angle (DAT) measurements. The methods presented in this thesis provide a new avenue towards better understanding of the behaviour of solid dispersions, which in turn may result in more effective distribution of promising drug candidates despite their low water-solubility.
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| 19. |
- Dahlberg, Carina, et al.
(författare)
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Polymer mobilization and drug release during tablet swelling. A 1H NMR and NMR microimaging study
- 2007
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Ingår i: Journal of Controlled Release. - : Elsevier BV. - 0168-3659 .- 1873-4995. ; 122, s. 199-205
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this study was to investigate the swelling characteristics of a hydroxypropyl methylcellulose (HPMC) matrix incorporating the hydrophilic drug antipyrine. We have used this matrix to introduce a novel analytical method, which allows us to obtain within one experimental setup information about the molecular processes of the polymer carrier and its impact on drug release. Nuclear magnetic resonance (NMR) imaging revealed in situ the swelling behavior of tablets when exposed to water. By using deuterated water, the spatial distribution and molecular dynamics of HPMC and their kinetics during swelling could be observed selectively. In parallel, NMR spectroscopy provided the concentration of the drug released into the aqueous phase. We find that both swelling and release are diffusion controlled. The ability of monitoring those two processes using the same experimental setup enables mapping their interconnection, which points on the importance and potential of this analytical technique for further application in other drug delivery forms.
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| 20. |
- Dahlberg, Carina, et al.
(författare)
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Polymer–drug interactions and wetting of solid dispersions
- 2009
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Ingår i: European Journal of Pharmaceutical Sciences. - : Elsevier BV. - 0928-0987 .- 1879-0720. ; 39:1-3, s. 125-133
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate the ability of drugs to influence the wetting of solid dispersion tablets in unexpected ways. Five model drugs of different water solubility and ability to interact with the involved polymers were incorporated in hydrophilic polymer matrices, made of either hydroxypropyl methylcellulose (HPMC) or polyvinyl pyrrolidone (PVP). The physical mixtures of all combinations of drug and polymer presented surface hydrophobicities, as measured by the equilibrium advancing contact angle of water, which are expected for materials that do not influence the interactions of each other with water. However, the solid dispersions containing HPMC deviated from this regular behaviour and displayed contact angles below those of the pure compounds involved, either drug or polymer. This behaviour is explained by changed surface exposure of HPMC side groups, as a result of changes in intermolecular hydrogen bonds. In addition to water contact angle measurements, we employed NMR imaging to monitor the time course of water ingress and swelling.
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