| 1. |
- Tikhomirov, Evgenii
(författare)
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Selective laser sintering for 3D printing of medications
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Suboptimal treatment caused by inaccurate dosing of prescribed medications is a challenging issue for the pharmaceutical industry. As a result, certain groups of patients, especially pediatric patients, may suffer from a lack of specific dosage forms, leading to potential side effects. To address this issue, various manipulation techniques are being applied, such as tablet crushing, splitting, and solution preparations. Unfortunately, these methods lack accuracy and economic efficiency.3D printing technology has been considered one of the potential solutions for manufacturing limited batch dosage forms. Dosage forms produced through 3D printing can be fabricated on demand for specific patients. Furthermore, the unique properties of these dosage forms, such as API amorphization, can be adjusted due to the high tunability of the 3D printing process. The work conducted in this thesis is dedicated to investigating the potential applications of Selective Laser Sintering (SLS) and the associated aspects of this method for manufacturing solid dosage forms.The investigations into printing parameters and formulation content enabled the establishment of correlations between these factors and the properties of the final dosage forms. Higher print temperature, Laser Power Ratio, and colorant concentration led to increased mass and hardness of the dosage forms.The polymer constitutes the major portion of the formulation in terms of mass. Consequently, various grades of polymer were examined to ascertain their chemical influence on the properties of the dosage forms. The findings revealed that the type of polymer, degree of hydrolysis, and dynamic viscosity of the polymer significantly impact both the dissolution rate and API amorphization.Utilizing FDM for printing the shell component of the drug delivery device improved its durability, whereas the SLS-printed insert resulted in a faster and adjustable dissolution rate. This experiment showcased the potential of combining the advantages of each technique to produce dosage forms with additional features.A thermal image analysis device was developed and employed to monitor temperature conditions throughout the printing process. The outcomes demonstrated that the collected data could be utilized for in-process quality control objectives and serve as a dataset for machine learning algorithms. This capability allows for real-time process monitoring, defect detection, and automated process refinement.In conclusion, a comprehensive study was conducted on the application of SLS and its limitations. This study will hopefully pave the way for further discussions and the implementation of this technology.
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| 2. |
- Åhlén, Michelle, 1992-
(författare)
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Porous Sorbents for Environmental Applications and Selective Laser Sintering 3D Printing of Dosage Forms
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The rising levels of greenhouse gas emissions from vehicular and industrial pollution constitute a serious concern not only for the environment but for our entire society. Traditional gas capture and separation techniques, such as amine scrubbing for CO2 gas separation, have been commonly used at a commercial scale, however issues relating to high costs and high energy requirements for sorbent regeneration have limited the efficiency of many of these techniques. The use of porous sorbents, such as metal-organic frameworks (MOFs), has garnered significant attention as an alternative method for the capture and separation of greenhouse gases in recent years, particularly due to their structural and functional tunability. Thus, part of this thesis explores the selective capture of CO2 and SF6 in five new MOFs and mixed-linker zeolitic imidazolate frameworks (ZIFs). The CO2 and SF6 adsorption in microporous bismuth-based MOFs containing narrow ultramicro-pores (e.g. UU-200) was not found to be correlated to the N2-accessible surface area of the framework but was related to pore size effects and possibly framework flexibility. Similar mechanisms for SF6 capture were observed in vanadium- and gallium-based MOFs (UU-201-4) in which an enhanced van der Waals interaction between the gas molecules and the pore surface was obtained due to the pore size of the materials coinciding with the kinetic diameter of SF6 (5.5 Å). This further resulted in good uptake capacities as well as SF6-over-N2 selectivites above 2.75 mmol g-1 and 43, respectively. Furthermore, the selective uptake of CO2 and SF6 could be modified in mixed-linker ZIF-7-8s by tuning of the pore aperture size through a controlled incorporation of the bulkier benzimidazolate linker in the frameworks.The removal of other environmental pollutants (e.g. phosphates) in porous materials such as amorphous mesoporous magnesium carbonate (MMC) was also investigated and showed that the material had superior sorption capacities as compared to its crystalline, non-porous counterpart. MMC was also found to be a capable functional support for other materials such as semiconducting TiO2 and ZnO nanoparticles. The TiO2/ZnO-composite was observed to retain the porosity as well as UV-blocking properties of the respective pristine materials.A part of this thesis was also devoted to the fabrication of personalized solid dosage forms for pharmaceutical applications. To achieve this, 3-dimensional selective laser sintering (SLS) printing was utilized to print both purely polymeric and drug-loaded tablets (containing 10 wt.% naproxen). The subsequent weight and mechanical strength of the obtained tablets could be tuned by either modifying the NIR-active pigment concentration in the powder formulation or by changing the laser energy input that is used during the printing process. Amorphization of the crystalline drug was also achieved in-situ during printing thus showing that the SLS 3D printing may be a promising technique for the manufacturing of solid amorphous dispersions with tailorable properties.
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| 3. |
- Sterby, Mia, 1989-
(författare)
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Electrochemical Characterizations of Conducting Redox Polymers : Electron Transport in PEDOT/Quinone Systems
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Organic electrode materials for rechargeable batteries have caught increasing attention since they can be used in new innovative applications such as flexible electronics and smart fabrics. They can provide safer and more environmentally friendly devices than traditional batteries made from metals. Conducting polymers constitute an interesting class of organic electrode materials that have been thoroughly studied for battery applications. They have high conductivity but are heavy relative to their energy storage ability and will hence form batteries with low weight capacity. Quinones, on the other hand, are low weight molecules that participate in electron transport in both animals and plants. They could provide batteries with high capacity but are easily dissolved in the electrolyte and have low conductivity. These two constituents can be combined into a conducting redox polymer that has both high conductivity and high capacity. In the present work, the conducting polymer PEDOT and the simplest quinone, benzoquinone, are covalently attached and form the conducting redox polymer used for most studies in this thesis. The charge transport mechanism is investigated by in situ conductivity measurements and is found to mainly be governed by band transport. Other properties such as packing, kinetics, mass changes, and spectral changes are also studied. A polymerization technique is also analyzed, that allows for polymerization from a deposited layer. Lastly, two different types of batteries using conducting redox polymers are constructed. The thesis gives insight into the fundamental properties of conducting redox polymers and paves the way for the future of organic electronics.
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| 4. |
- Alvebratt, Caroline
(författare)
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Advanced Methods for Evaluation of the Performance of Complex Drug Delivery System
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Low oral bioavailability of drugs originating from poor aqueous solubility is a common issue in drug development. Various enabling formulations have been presented to circumvent this limitation, many making use of supersaturation. In these, the drug is delivered to the gastro-intestinal lumen in a high energy state e.g. in amorphous form or a liquid lipid vehicle. Concentrations surpassing the equilibrium solubility of the crystalline drug are achieved, which facilitate increased absorption for dissolution-rate limited compounds. Meanwhile the use of the enabling formulation can be beneficial to increase the bioavailability of poorly water-soluble drugs, in vitro evaluation of these systems remain challenging. Limited methods have also evaluated several different types of enabling formulation in the same experimental setup. The overall aim of this thesis was therefore to develop assays to study the performance of various complex drug delivery systems. In the first part, a small scale dissolution apparatus, the µDiss Profiler, was used to study drug release from drug-loaded mesoporous magnesium carbonate (MMC). A protective filter was developed to minimize particle interference on the UV-measurements, enabling studies of supersaturation from the amorphous carrier. In the second paper, lipids were adsorbed onto the MMC. A modified in vitro lipolysis setup was established and the samples were analyzed with nuclear magnetic resonance spectroscopy. A stability study of the lipid-loaded MMC was also performed. The methods developed in the first two projects provided an insight to events occurring in the intestinal lumen. The intestinal absorption has however been shown to be a complex interplay between dissolution-digestion and permeation. In the final two projects, two devices comprising of a donor (luminal) chamber and a receiver (serosal) chamber were studied (the µFLUX and the enabling absorption, ENA, device). The two chambers were separated by a semipermeable membrane (cell-based and/or phospholipid-based). A wide range of enabling formulations were evaluated in the two assays. As the exposure in the donor correlated poorly with the exposure in the receiver compartment, this emphasizes the importance of in vitro methods taking both the dissolution-digestion and permeation into account. The ENA results also predicted the in vivo performance in rats well. To conclude, several models have been established in the thesis to study the in vitro performance of enabling formulations, which will be valuable for screening of appropriate drug delivery systems.
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| 5. |
- Kong, Xueying, 1993-
(författare)
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Porous Materials and Their Cellulose-Based Composites : Synthesis, Nanoengineering, and Applications
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Porous materials, such as porous carbons (PCs), metal-organic frameworks (MOFs), and covalent organic frameworks (COFs), show considerable potential across various fields because of their rich microporous and mesoporous structures and large surface areas, yet they grapple with challenges like environmentally unfriendly fabrication methods and poor processability. In this thesis, we investigated environmentally friendly fabrication methods for porous materials, nanoengineering techniques for processing these materials, and their potential applications.Cladophora cellulose (CC), a naturally abundant biopolymer, was used to prepare PC via a one-step physical carbonization/activation method without using any corrosive activation agents. The obtained CC-derived PC (CPC) showed a high specific surface area (507.2 m2 g−1) and rich microporous structure. Additionally, we introduced a simple and environmentally friendly method for synthesizing imine-linked COFs at room temperature using water as the solvent. The method involves a key step in which aldehyde monomers are pre-activated by acetic acid, which promotes the aldehyde monomers to dissolve in water, enhancing their reactivity with amine monomers, and ensuring the formation of crystalline COFs. Consequently, we synthesized 16 distinct imine-linked COFs with high crystallinity and specific surface areas. Furthermore, this thesis focusses on improving the poor processability of these materials caused by the infusible and insoluble nature of their powders. The poor processability of these porous materials makes them difficult to process into desired structures and shapes. Here, we introduce two nanoengineering methods: i) Interweaving porous materials with CC nanofibers (CNFs) to form CNF-porous material aqueous solutions; and ii) Interfacial synthesis of porous materials on the surface of carboxylated CNFs to form CNF@porous materials with nanofiber structures in aqueous solutions. The obtained composite suspensions can be fabricated into freestanding and flexible composite nanopapers via a vacuum filtration and drying process. In addition, they can be processed into freestanding aerogels through a freeze-drying process. Consequently, we have successfully prepared freestanding and flexible CC-CPC nanopapers and CC-CPC aerogels, c-CNT@COF/CNT/CNF nanopapers (c-CNT: carboxylated carbon nanotube), CNF@MOF nanopapers, and CNF@COF nanopapers and demonstrated their potential in various applications, from efficient CO2 capture and organic pollutant removal to advanced energy storage and solar vapor generation. In summary, we used environmentally friendly methods to synthesize PC and imine-linked COFs, circumventing the need for corrosive chemical agents and toxic organic solvents, respectively. Furthermore, by combining CNFs with porous materials, we successfully created freestanding and flexible nanopapers and aerogels, thereby addressing the issue of poor processability associated with porous materials.
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| 6. |
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| 7. |
- Hu, Lei, et al.
(författare)
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Molecular surface modification of silver chalcogenolate clusters
- 2022
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Ingår i: Dalton Trans.. - : Royal Society of Chemistry (RSC). ; 51, s. 3241-3247
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Tidskriftsartikel (refereegranskat)abstract
- This study presents a molecular surface modification approach to synthesizing a family of silver chalcogenolate clusters (SCCs) containing the same [Ag12S6] core and different surface-bonded organic ligands (DMAc or pyridines; DMAc = dimethylacetamide), with the aim of tuning the luminescence property and increasing the structural stability of the SCCs. The SCCs displayed strong and tuneable luminescence emissions at 77 K (from green to orange to red) as influenced by the peripheral pyridine ligands. In addition, SCC 5 protected by pyridine molecules was stable in ambient air, humid air and even liquid water for a long time (up to 1 week), and it was more structurally stable than SCC 1 bonded with DMAc molecules under the same conditions. The high structural stability of SCC 5 can be explained by the ability of pyridine molecules to form strong coordination bonds with silver atoms. This study offers a new way of designing structurally stable metal nanoclusters with tuneable physicochemical properties.
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| 8. |
- Kong, Xueying, et al.
(författare)
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All-cellulose-based freestanding porous carbon nanocomposites and their versatile applications
- 2022
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Ingår i: Composites Part B. - : Elsevier. - 1359-8368 .- 1879-1069. ; 232
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Tidskriftsartikel (refereegranskat)abstract
- Porous carbons are key functional materials in a range of industrial processes such as gas adsorption and separation, water treatment, and energy conversion and storage. It is, however, important from a sustainability perspective for porous carbons to be synthesized from naturally abundant biopolymers. Nanoengineering of porous carbons using facile binder-free techniques presents significant challenges, but is deemed beneficial for broadening their field of use and improving their application performance. This paper discusses the processing of cellulose-based porous carbons interwoven with cellulose nanofibers to fabricate freestanding nanopapers and aerogels, aiming at developing processable, fully sustainable, and all-cellulose-based carbon nanocomposites. The aerogels, which have cellular networks, low density and high mechanical strength, were investigated as sorbents for CO2 capture and removal of various organics. The presence of rich ultramicropores allows the aerogels to adsorb relatively high amounts of CO2, with high selectivity of CO2-over-N-2 (up to 111). More importantly, the sorbents have high CO2 working capacities and excellent recyclability under temperature swing adsorption conditions. In addition, the aerogels can adsorb various organic solvents remarkably well, corresponding to 100-217 times their own weight. The nanopapers are active photothermal materials that can be applied as solar absorbers for interfacial solar vapor generation, providing a high evaporation rate (1.74 kg m(-2) h(-1) under one sun illumination). The nanopapers were also employed as electrodes in flexible, foldable super capacitors with high areal capacitances. This study may provide a basis for further development of and new application areas for all-cellulose-based nanocomposites.
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| 9. |
- Kong, Xueying, et al.
(författare)
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Ambient Aqueous Synthesis of Imine-Linked Covalent Organic Frameworks (COFs) and Fabrication of Freestanding Cellulose Nanofiber@COF Nanopapers
- 2023
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 146:1, s. 742-751
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Tidskriftsartikel (refereegranskat)abstract
- Covalent organic frameworks (COFs) are usually synthesized under solvothermal conditions that require the use of toxic organic solvents, high reaction temperatures, and complicated procedures. Additionally, their insolubility and infusibility present substantial challenges in the processing of COFs. Herein, we report a facile, green approach for the synthesis of imine-linked COFs in an aqueous solution at room temperature. The key behind the synthesis is the regulation of the reaction rate. The preactivation of aldehyde monomers using acetic acid significantly enhances their reactivity in aqueous solutions. Meanwhile, the still somewhat lower imine formation rate and higher imine breaking rates in aqueous solution, in contrast to conventional solvothermal synthesis, allow for the modulation of the reaction equilibrium and the crystallization of the products. As a result, highly crystalline COFs with large surface areas can be formed in relatively high yields in a few minutes. In total, 16 COFs are successfully synthesized from monomers with different molecular sizes, geometries, pendant groups, and core structures, demonstrating the versatility of this approach. Notably, this method works well on the gram scale synthesis of COFs. Furthermore, the aqueous synthesis facilitates the interfacial growth of COF nanolayers on the surface of cellulose nanofibers (CNFs). The resulting CNF@COF hybrid nanofibers can be easily processed into freestanding nanopapers, demonstrating high efficiency in removing trace amounts of antibiotics from wastewater. This study provides a route to the green synthesis and processing of various COFs, paving the way for practical applications in diverse fields.
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| 10. |
- Kong, Xueying, et al.
(författare)
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Aqueous synthesis and engineering of imine-linked covalent organic frameworks
- 2023
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Ingår i: One-day symposium: Sorption, Transport and Catalysis in Metal-Organic Frameworks. Uppsala 18/9 2023. - Uppsala.
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Konferensbidrag (refereegranskat)abstract
- Covalent organic frameworks (COFs) are typically synthesized through solvothermal methods, which necessitate the use of hazardous organic solvents, elevated reaction temperatures, and intricate procedures. Additionally, their insolubility and inability to melt present substantial challenges in the processing of COFs. In this study, we present an eco-friendly method for synthesizing imine-linked COFs by simply stirring the initial materials in an aqueous solution at room temperature. A key element of this approach involves the pre-activation of aldehyde monomers using acetic acid, significantly enhancing their reactivity in aqueous solutions. This innovative strategy results in the rapid formation of highly crystalline COFs formed at relatively high yields, with substantial surface areas, within minutes. Remarkably, this method performs exceptionally well on a gram-scale, producing highly crystalline and porous COFs in scaled-up reactions.We successfully synthesized a total of 15 COFs using monomers with diverse molecular sizes, geometries, pendant groups, and core structures, underscoring the versatility of this approach. Furthermore, our use of cellulose nanofibers (CNFs) as a substrate during the syntheses allows for the growth of COF nanolayers on the CNF surface. These CNF@COF hybrid nanofibers can be effortlessly transformed into freestanding nanopapers.Significantly, both COF powders and CNF@COF nanopapers exhibit remarkable efficiency in removing trace amounts of antibiotics from wastewater. This research offers a promising avenue for the green synthesis and processing of various COFs, paving the way for practical applications in diverse fields.
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