| 1. |
- Kilpijärvi, Joni
(författare)
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RF-microwave sensor development for cell and human in vitro and ex vivo monitoring
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this research new RF/microwave-based sensor solutions were developed for the monitoring of biological cells and human beings to obtain a better understanding of their activity or state in a quick, cheap, easy and continuous way. The effect of different substances on cell behaviour can be monitored by measuring the electrical environment where changes are observed as cells react to a stimulus. The starting point of the study was a microchip with a capacitance measurement system integrated into the culturing chamber, enabling the monitoring of cell proliferation or death. The main challenge of the study was the correct interpretation of the received signals and the combination of “dry” electronics and “wet” biology, which is a difficult issue in terms of reliability and durability of the system. For this purpose, a low temperature co-fired ceramic package was developed which could withstand cell culture conditions and which did not interfere with the cell activity. A 1.1 MHz shift in resonance frequency of the system could clearly be measured, where the shift depended on the number of cells. Another topic of the research concentrated on a microwave sensor that can be utilized in the examination and analysis of fluid samples collected from the body which provide information about a person’s health status. A microwave sensor was developed, which was tested with liquid samples. Microfluidics were also integrated into the system which allowed the use of very small sample volumes and improved the usability of the device. The challenge of the work was to build the system so that the parts were integrated seamlessly without interfering with each other. The sensor concept was tested successfully using typical concentrations of NaCl found in human blood plasma i.e. 125 to 155 mmol/mol of water. The third topic of the thesis was aiming for a microwave sensor that enables real-time measurement of body fluid balance directly from the skin. The operation of the developed microwave sensor was based on a resonator whose resonance frequency reacted to the electrical properties of materials in its proximity, in this case the water content of the skin and its changes. The function of the sensor was tested with artificial skin, made in the laboratory, which corresponded to the properties of real skin. The observed changes in resonance frequency was +370 MHz and -220 MHz for dehydrated and hydrated skin compared to normal skin, thus providing a wide frequency range for detection of the status of the skin.
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| 2. |
- Eriksson, Peter, 1989-
(författare)
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Cerium Oxide Nanoparticles and Gadolinium Integration : Synthesis, Characterization and Biomedical Applications
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A challenging task, in the area of magnetic resonance imaging is to develop contrast enhancers with built-in antioxidant properties. Oxidative stress is considered to be involved in the onset and progression of several serious conditions such as Alzheimer’s and Parkinson’s disease, and the possibility to use cerium-contained nanoparticles to modulate such inflammatory response has gained a lot of interest lately. The rare earth element gadolinium is, due to its seven unpaired f-electrons and high symmetry of the electronic state, a powerful element for contrast enhancement in magnetic resonance imaging. Chelates based on gadolinium are the most commonly used contrast agents worldwide. When introducing external contrast agents there is always a risk that it may trigger inflammatory responses, why there is an urgent need for new, tailor-made contrast agents.Small sized cerium oxide nanoparticles have electronic structures that allows coexistence of oxidation states 3+ and 4+ of cerium, which correlates to applicable redox reactions in biomedicine. Such cerium oxide nanoparticles have recently shown to exhibit antioxidant properties both in vitro and in vivo, via the mechanisms involving enzyme mimicking activity.This PhD project is a comprehensive investigation of cerium oxide nanoparticles as scaffold materials for gadolinium integration. Gadolinium is well adopted into the crystal structure of cerium oxide, enabling the combination of diagnostic and therapeutic properties into a single nanoparticle. The main focus of this thesis project is to design cerium oxide nanoparticles with gadolinium integration. A stepwise approach was employed as follows: 1) synthesis with controlled integration of gadolinium, 2) material characterization by means of composition crystal structure, size, and size distribution and 3) surface modification for stabilization. The obtained nanoparticles exhibit remarkable antioxidant capability in vitro and in vivo. They deliver strongly enhanced contrast per gadolinium in magnetic resonance imaging, compared to commercially available contrast agents.A soft shell of dextran is introduced to encapsulate the cerium oxide nanoparticles with integrated gadolinium, which protects and stabilizes the hard core and to increases their biocompatibility. The dextran-coating is clearly shown to reduce formation of a protein corona and it improves the dispersibility of the nanoparticles in cell media. Functionalization strategies are currently being studied to endow these nanoparticles with specific tags for targeting purposes. This will enable guidance of the nanoparticles to a specific tissue, for high local magnetic resonance contrast complemented with properties for on-site reduced inflammation.In conclusion, our cerium oxide nanoparticles with integrated gadolinium, exhibit combined therapeutic and diagnostic, i.e. theragnostic capabilities. This type of nanomaterial is highly promising for applications in the field of biomedical imaging.
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| 3. |
- Abrikossova, Natalia, 1965-
(författare)
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Investigation of nanoparticle-cell interactions for development of next generation of biocompatible MRI contrast agents
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Progress in synthesis technologies and advances in fundamental understanding of materials with low dimensionality has led to the birth of a new scientific field, nanoscience, and to strong expectations of multiple applications of nanomaterials. The physical properties of small particles are unique, bridging the gap between atoms and molecules, on one side, and bulk materials on the other side. The work presented in this thesis investigates the potential of using magnetic nanoparticles as the next generation of contrast agents for biomedical imaging. The focus is on gadolinium-based nanoparticles and cellular activity including the uptake, morphology and production of reactive oxygen species.Gd ion complexes, like Gd chelates, are used today in the clinic, world-wide. However, there is a need for novel agents, with improved contrast capabilities and increased biocompatibility. One avenue in their design is based on crystalline nanoparticles. It allows to reduce the total number of Gd ions needed for an examination. This can be done by nanotechnology, which allows one to improve and fine tune the physico- chemical properties on the nanomaterial in use, and to increase the number of Gd atoms at a specific site that interact with protons and thereby locally increase the signal. In the present work, synthesis, purification and surface modification of crystalline Gd2O3-based nanoparticles have been performed. The nanoparticles are selected on the basis of their physical properties, that is they show enhanced magnetic properties and therefore may be of high potential interest for applications as contrast agents.The main synthesis method of Gd2O3 nanoparticles in this work was the modified “polyol” route, followed by purification of as-synthesized DEG-Gd2O3 nanoparticles suspensions. In most cases the purification step involved dialysis of the nanoparticle samples. In this thesis, organosilane were chosen as an exchange agent for further functionalization. Moreover, several paths have been explored for modification of the nanoparticles, including Tb3+ doping and capping with sorbitol.Biocompatibility of the newly designed nanoparticles is a prerequisite for their use in medical applications. Its evaluation is a complex process involving a wide range of biological phenomena. A promising path adopted in this work is to study of nanoparticle interactions with isolated blood cells. In this way one could screen nanomaterial prior to animal studies.The primary cell type considered in the thesis are polymorphonuclear neutrophils (PMN) which represent a type of the cells of human blood belonging to the granulocyte family of leukocytes. PMNs act as the first defense of the immune system against invading pathogens, which makes them valuable for studies of biocompatibility of newly synthesized nanoparticles. In addition, an immortalized murine alveolar macrophage cell line (MH-S), THP-1 cell line, and Ba/F3 murine bone marrow-derived cell line were considered to investigate the optimization of the cell uptake and to examine the potential of new intracellular contrast agent for magnetic resonance imaging. In paper I, the nanoparticles were investigated in a cellular system, as potential probes for visualization and targeting intended for bioimaging applications. The production of reactive oxygen species (ROS) by means of luminol-dependent chemiluminescence from human neutrophils was studied in presence of Gd2O3 nanoparticles. In paper II, a new design of functionalized ultra-small rare earth-based nanoparticles was reported. The synthesis was done using polyol method followed by PEGylation, and dialysis. Supersmall gadolinium oxide (DEG-Gd2O3) nanoparticles, in the range of 3-5 nm were obtained and carefully characterized. Neutrophil activation after exposure to this nanomaterial was studied by means of fluorescence microscopy. In paper III, cell labeling with Gd2O3 nanoparticles in hematopoietic cells was monitored by magnetic resonance imaging (MRI). In paper IV, ultra-small gadolinium oxide nanoparticles doped with terbium ions were synthesized as a potentially bifunctional material with both fluorescent and magnetic contrast agent properties. Paramagnetic behavior was studied. MRI contrast enhancement was received, and the luminescent/ fluorescent property of the particles was attributable to the Tb3+ ion located on the crystal lattice of the Gd2O3 host. Fluorescent labeling of living cells was obtained. In manuscript V, neutrophil granulocytes were investigated with rapid cell signaling communicative processes in time frame of minutes, and their response to cerium-oxide based nanoparticles were monitored using capacitive sensors based on Lab-on-a-chip technology. This showed the potential of label free method used to measure oxidative stress of neutrophil granulocytes. In manuscript VI, investigations of cell-(DEGGd2O3) nanoparticle interactions were carried out. Plain (DEG-Gd2O3) nanoparticles, (DEG-Gd2O3) nanoparticles in presence of sorbitol and (DEG-Gd2O3) nanoparticles capped with sorbitol were studied. Relaxation studies and measurements of the reactive oxygen species production by neutrophils were based on chemiluminescence. Cell morphology was evaluated as a parameter of the nanoparticle induced inflammatory response by means of the fluorescence microscopy.The thesis demonstrates high potential of novel Gd2O3-based nanoparticles for development of the next generation contrast agents, that is to find biocompatible compounds with high relaxivity that can be detected at lower doses, and in the future enable targeting to provide great local contrast.
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| 4. |
- Balian, Alien, 1988-
(författare)
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Nuclease Activity as a Biomarker in Cancer Detection
- 2023
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Nucleases are a group of enzymes that cleave the phosphodiester bonds in nucleic acids. As such, nucleases act as biological scissors that exhibit a plethora of fundamental roles, in prokaryotes and eukaryotes, dependent or non-dependent on their catalytic capability. Thus, differential status of nucleases between healthy and disease conditions might not be surprising, and can be deployed in disease detection. Specifically, there is growing body of research demonstrating the potential of nucleases as diagnostic biomarkers in several types of cancer. Biomarkers for early diagnosis are an immense need in the diagnostic landscape of cancer. In this sense, nucleases are promising biomolecules, and they possess a unique feature of catalytic activity that could be deployed for diagnosis and future therapeutic strategies. In this thesis we aim to demonstrate the use of nucleases as biomarkers associated to cancer, and the capability of oligonucleotide substrates for targeting a specific nuclease. The thesis work begins with comprehensive review of nucleases as promising biomarkers in cancer diagnosis (paper I). Then, we provide a methodological study in paper II, in which we propose a flexible approach for detection of disease associated nuclease activity using oligonucleotides as substrates. The probes utilized here are flanked with fluorophore at the 5’-end and a quencher at the 3’-end. Upon cleavage by nucleases, the fluorescent signal is increased in a proportional fashion to nuclease activity. This platform is suitable to implement in detection of any disease in which nuclease activity is altered. We have applied this method in paper III, by using 75 probes as substrates to screen breast cancer cells, along with controls, for nuclease activity. We have identified a probe (DNA PolyAT) that discriminates between BT-474 breast cancer cells and healthy cells based on nuclease activity profile associated with cell membrane. Next, we screened tissue samples from breast tumors for nuclease activity, and we have identified a set of probes with the capability to discriminate breast tumor and healthy tissues in 89% of the cases (paper IV). To achieve a step forward towards non-invasive diagnosis, we have developed an activatable magnetic resonance imaging (MRI)-probe (paper V). The MRI-probe is oligonucleotide-based that works like a contrast agent, and it is activated only in presence of a specific nuclease. MRI-probes provide advantages over fluorescent probes, such as high spatial resolution and unlimited tissue penetration. In conclusion, our findings suggest the utility of nuclease activity as a biomarker in cancer detection. Moreover, we demonstrate the applicability of nuclease activity-based approaches in imaging modalities, such as MRI. Our future aim is to translate our findings into non-invasive detection of breast cancer by utilizing breast cancer activatable MRI-probes.
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| 5. |
- Bunnfors, Kalle, 1989-
(författare)
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Imaging and Spectroscopic Mapping of Blood Cell Activity : Nanoparticles and Neutrophil Extracellular Traps
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Imaging and visualization of cell activity when exposed to nanomaterial are of main importance, when investigating biological response to a wide range of biomaterials from medical implants to smart nanoprobes. The ability to provide molecular and chemical information with spatial resolution in the region of sub-µm leads to increased insight and understanding of these biological challenges. Interdisciplinary collaborative effort may contribute and help solving urgent matters related to the challenges that we globally share. It is necessary to develop powerful tools such as analytical imaging techniques for addressing these urgent issues. This will increase our knowledge from the visualization on the cellular and subcellular level and help designing sustainable, personalized medical nanoprobes. In this thesis, the focus is to investigate the possibilities using the fluorescence microscopy, combined with surface analytical techniques delivering element specific information. Neutrophils are the most abundant immune cell in our bodies. They scavenge the body for threats and are usually among the first ones to find intruders and start the inflammation process. They have several ways of handling a threat, the main three being degranulation, phagocytosis, and neutrophil extracellular traps (NETs). In short, degranulation where granules are released into the extracellular matrix, phagocytosis is the process when for example the bacteria in engulfed by the neutrophil and neutralized. The NETs are when the neutrophil decondense their DNA and throw it out as a net to physically trap the invader and together with reactive oxygen species, proteases, and other antimicrobial molecules. It has been observed that nanoparticles (NP) can trigger NETs and there have been some comparisons between different parameters such as size, geometry, and functionalization. In this thesis we have explored how to measure neutrophil activity by a novel label free and noninvasive method (Paper 1). The NanoEsca, a combined XPS and PEEM instrument, is used to chemically map the neutrophils and NETs. We could clearly observe the NETs in PEEM and XPS mode. Quantum Dots (QDots, CdSe based) was used to trigger NETs. We track down the Quantum Dots with the element specific mapping. In the next paper we further explored how to extract new information with this advanced instrument that is traditionally is used for material- and surface science, and just recently deliver results in imaging and visualization within life sciences. Ultrathin slices of neutrophils where made special focus was given to the research work developing strategies to obtain and extract additional information from inside the neutrophils. These are pilot studies and show great potential to get chemical information in a label free way and is a good complement to fluorescence, SEM and TEM. We then made an in-depth investigation on the mechanisms how nanoparticles interact with neutrophils, with special focus on processes triggering NETs formation. Using QDots as a model system we could show that the NETs release is strongly dependent on the uptake of the nanoparticles. We used fluorescence and TEM to investigate where the QDots uptake and to identify the pattern where they finally end up. We clearly observed them inside vesicles in the inner part of the cell and even within the NETs structure giving proof that the uptake of QDots play an important role of the NETs formation. In the last paper we expanded the study and exposed the cells to Iron Oxide NPs (FeNP) Here we developed a strategy how to alternate the magnetic field control the direction of the NETs. We could manipulate live NETs with a magnetic field and made observations that parts of the NETs are static and some clearly mobile, still with an internal memory to find its initial structure just after release. TEM studies revealed that, like the QDots, the FeNP end up inside the NETs. In conclusion in this thesis work, detailed processes are explored on neutrophils and their NETs formation with new unconventional methods and how neutrophils and nanoparticles interact with respect to NETs.
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| 6. |
- Poot, Thirza
(författare)
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Sustainable Surface Functionalization of Lightweight Materials : Cerium Oxide Nanoparticles Replacing Chromium in Anodic Coatings and Carbon Nanomaterials for Lightning Strike Protection
- 2022
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Aviation accounts for 2-3% of the carbon dioxide emitted globally. One way to reduce emissions is to develop and introduce sustainable, functional, lightweight materials and coatings that increase the lifetime and fuel efficiency of aircraft. The main lightweight materials used in the aerospace industry today are aluminum alloys and carbon fiber reinforced plastic composites. In the work presented in this licentiate thesis, a new sustainable alternative for the replacement of toxic hexavalent chromium in a low energy and chemical consumption sealing procedure of anodized aluminum alloys is suggested (paper I and II). An alternative to the conventional metal mesh used as lightning strike protection for composite structures used today is also presented. The proposed solution adds considerably less weight and has a possibility to reduce the CO2 emission from aviation (paper III). Aluminum alloys as well as composites both exhibit high strength-to-weight ratios but come with individual drawbacks. Fiber reinforced plastics exhibit limited electrical conductivity, which is why additional protection is needed to avoid severe damage following a lightning strike. Aluminum alloys have instead the disadvantage of being susceptible to corrosion and surface protection is required to prolong the materials lifetime and to avoid devastating failures. Anodization, formation of a porous aluminum oxide coating, is the most common choice of surface treatment. This is often followed by closure of the pores through a sealing procedure. Both processes have up until recently been performed in large, energy consuming tanks with highly toxic solutions containing hexavalent chromium which must be replaced to reduce the environmental impact. In paper I, the environmentally friendly tartaric sulfuric acid has been used as anodization electrolyte and cerium oxide nanoparticles have been investigated as a promising alternative for sealing. Cerium-based and hydrothermal sealing (immersion in hot water), individually and combined, were investigated. The morphological and chemical composition were studied by means of scanning electron microscopy, scanning transmission electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The investigation confirmed the growth of cerium oxide nanoparticles throughout the coating and closing of the pores by hydrothermal sealing. A corrosion immersion test revealed a superior corrosion resistance of surfaces treated with the two-step sealing process compared to plain anodized, cerium or hydrothermally sealed surfaces. In paper II, the potential use of an aerosol-based wet thin film coating technique called nFOG for cerium sealing as a low chemical and energy consumption alternative to traditional bath-type sealing was investigated. Characterizations of the morphology and composition reveal cerium oxide nanoparticles evenly distributed within the porous coating by the nFOG technique. The new application of the nFOG method was also shown to provide anti-corrosion properties comparable to bath-type sealing. This wet coating technique has the potential to replace chromium and reduce the environmental impact in the treatment process. Furthermore, the limited electrical conductivity of carbon fiber reinforced plastics can be circumvented by loading the polymer matrix of the composite structure (commonly epoxy) with highly conductive carbon nanomaterials. In paper III, graphene nanoplatelets and carbon nanotubes were loaded into the epoxy. Simulated lightning strike tests showed an improved damage tolerance for the loaded composites compared to composites prepared with plain epoxy. The results suggest that a combination of graphene nanoplatelets and carbon nanotubes increases the damage tolerance by carrying the resulting high electric current from a lightning strike. In conclusion, the application of cerium oxide nanoparticles and carbon nanomaterials moves the aerospace industry towards a sustainable fuel efficiency using functional, lightweight materials and coatings.
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| 7. |
- Rodner, Marius, 1991-
(författare)
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Towards a versatile gas sensing platform with epitaxial graphene
- 2019
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The work presented in this thesis focuses on how to utilize epitaxially grown graphene on SiC as a basis for ultra-sensitive gas sensor. Several approaches have been tested and evaluated to increase the sensitivity, selectivity, speed of response and stability and of the graphene based gas sensors with a focus on air quality monitoring applications. The graphene surfaces have been functionalized with different metal oxide nanoparticles and nanolayers using hollow-cathode sputtering and pulsed laser deposition. The modified surface was investigated towards its topography, integrity and chemical composition with characterization methods such as AFM, Raman and XPS. Moreover, the binding energy was calculated with density functional theory for benzene and formaldehyde when reacting with pristine epitaxial graphene and iron oxide nanoparticle decorated graphene to verify the usefulness of this approach. The impact of environmental influences such as operating temperature, relative humidity and UV irradiation towards sensing properties was investigated as well. To further decrease time constants, the first-order time-derivative of the sensor’s resistance is introduced as an alternative sensor signal and evaluated towards its applicability.Applying these methods in laboratory conditions, sensors with a quantitative readout of single ppb benzene and formaldehyde were developed and time constants of less than one minute could be achieved with the first-order time-derivative signal. These results show promise to fill the existing gap of low-cost but highly sensitive and fast gas sensors for air quality monitoring.
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| 8. |
- Skallberg, Andreas, 1983-
(författare)
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Photoemission and Characterization of Neutrophils and Nanoparticles : Energy Mapping and Elemental Composition with sub-µm Resolution
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Imaging and visualization of cells and tissues are important when studying various biological phenomena. The ability to provide spatial information with molecular and chemical specificity may increase our insight and understanding of biological problems within life sciences. There is a need for well suited analytical imaging tools for addressing challenges that can increase our knowledge from the visualization on the cellular and subcellular level. In this thesis, we have focused on the use of surface analytical techniques based on the photoemission process. Synchrotron based surface analytical tools such as mirror electron microscopy, low energy electron microscopy, X-ray photoelectron spectroscopy, X-ray photoemission electron microscopy and near edge X-ray absorption fine structure spectroscopy were used to obtain highly resolved chemical information for both fundamental biological systems and technical innovations.A combined photoemission electron microscopy and imaging X-ray photoelectron spectroscopy instrument have been used for visualization and characterization of neutrophils attached to silicon and gold surfaces. Neutrophils are white blood cells and a major part of our innate immune system. In the body they circulate and scavenge for possible threats, such as pathogens. The neutrophils possess three main defense mechanisms to tackle any possible threat in the body. One of these mechanisms is the release and formation of extracellular traps used for entrapping and capturing. We have visualized the extracellular trap formation in presence of nanoparticles and images of the neutrophils have been obtained with threshold mapping and work function contrast from energy-filtering operations together with element specific imaging and chemical maps. We demonstrated work function variation in imaging mode for the cellular morphology and the characteristic polymorphonuclear morphology of the nucleus. These results demonstrate the potential and extend the use of photoemission electron microscopy and imaging X-ray photoelectron spectroscopy as analytical tools for visualization of biological materials and processes on the cellular level.The use of nanoparticles in recent years have significantly increased. Today, nanoparticles are being used in a wide range of applications, such as in electronics, energy, biology, and medicine. One hot topic in medicine is the development of contrast enhancement agents for magnetic resonance imaging. We report the development of two types of nanoparticles to be used as contrast enhancers for magnetic resonance imaging. The first type is water-dispersible and ultra-small Fe3O4 nanoparticles coated with polyacrylic acid. The Fe3O4 nanoparticles exhibit good magnetic properties, biocompatibility, excellent relaxivity properties and can be employed as a potential dual T1 and T2 weighted contrast agent. The second type is cerium oxide nanoparticles with the integration of gadolinium. Cerium oxide has unique redox properties due to the coexistence of Ce3+ and Ce4+ states making them suitable for scavenging reactive oxygen species. The integration of gadolinium makes these nanoparticles promising contrast agents with both therapeutic and diagnostic properties. We have designed a new technical innovative energy saving process where a reduction in the annealing temperature for oxide removal is obtained, by the presence of europium doped gadolinium oxide nanoparticles in comparison to Eu3+ and Gd3+. A low coverage of nanoparticles and ions revealed a significant reduction in annealing temperature for the oxide removal. These results deliver a promising one step energy saving strategy of producing silicon-based contacts. In summary, this thesis work demonstrates the power of element specific imaging and chemical mapping of bio-related surfaces as well as nanoparticle tracking in the sub-micro and nano region.
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| 9. |
- Zhang, Xin, 1990-
(författare)
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Tailoring Fluorescent Probes for Organelle-Specific Imaging and Sensing
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Exploring and visualizing biological and pathological processes in living cells are useful for both fundamental research and applications. An understanding on the molecular level for these processes with focus on tracking biomarkers, collecting information about their surroundings, and uncovering essential molecular pathways and functions in live cells are of vital interest for cell biological study and clinical diagnosis application. Fluorescent imaging technologies have become essential tools in cell biology studies, providing dynamic information about the localization and quantity of the analytes in living systems that we can not see by our naked eyes. Since the discovery of organic fluorescent dyes, unremitting efforts have been made to visualize the behaviors of specific targets by using these fluorophores as labels. Today, a variety of probes and nanoprobes have been developed for specific targeting and sensing. However, the current probes and nanoprobes still show some inherent deficiencies, such as poor specificity, strong photobleaching, high toxicity, low signal-to-noise ratio, poor cell membrane penetration, etc. To conquer these limitations, this thesis will focus on developing fluorescent platforms for bioimaging and biosensing with improved sensitivity, selectivity, specificity, and stability.A red-emitting fluorescent probe is first proposed that not only tracks the dynamic changes in real-time, during migration and fusion of lipid droplets but also monitors starvation-induced lipophagy (Paper I). In addition to organic fluorophores, hybrid fluorescent silica nanoparticles (SiNPs) are very promising for bioimaging/sensing owing to the advantages of low toxicity, high biocompatibility, multifunctionality, hydrophilicity and accessible surface functionality. Nonetheless, to apply SiNPs for such purposes, it is mandatory to address common problems of poor cell penetration and lack of specificity. Therefore, in this thesis, an efficient membrane-penetration SiNP is tailored with the intention to enable subcellular imaging/sensing. The proposed SiNPs are characterized by rapid cellular uptake (˂ 30 min) and specific subcellular targeting capabilities with surface modification. Finally, real-time tracking of dynamic changes in mitochondria and lysosomes during autophagy process is successfully performed (Paper II). Through the rational design of new functionalities on the established SiNPs, mitochondria- and lysosome-specific pH nanoprobes are further tailored for real-time monitoring of pH variations under various stimuli (Paper III and IV). Another ratiometric nanoprobe is developed for quantitative indication of lysosomal adenosine 5'-triphosphate (ATP) levels in living cells. The nanoprobe enables a deeper understanding of the interplay between energy metabolism and autophagy (Paper V).In conclusion, throughout the studies in this thesis, the fabrication and utilization of fluorescent molecular probes and SiNP-based nanoprobes for cellular probing have been investigated and analyzed. The strategies and the fabricated SiNPs can facilitate our deeper understanding of cellular pathological processes and provide basic knowledge for the development of other functional materials for life science applications.
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| 10. |
- Rodner, Marius, 1991-, et al.
(författare)
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Iron oxide nanoparticle decorated graphene for ultra-sensitive detection of volatile organic compounds
- 2018
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Ingår i: Proceedings. - Basel Switzerland : MDPI. - 2504-3900. ; 2:13
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Tidskriftsartikel (refereegranskat)abstract
- It has been found that two-dimensional materials, such as graphene, can be used as remarkable gas detection platforms as even minimal chemical interactions can lead to distinct changes in electrical conductivity. In this work, epitaxially grown graphene was decorated with iron oxide nanoparticles for sensor performance tuning. This hybrid surface was used as a sensing layer to detect formaldehyde and benzene at concentrations of relevance in air quality monitoring (low parts per billion). Moreover, the time constants could be drastically reduced using a derivative sensor signal readout, allowing detection at the sampling rates desired for air quality monitoring applications.
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