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Model-based design and the implementation of dosing and blending unit-operations for continuous direct compression
Get PDFThis thesis presents a comprehensive investigation and implementation of models for individual process units within a continuous dosing and blending module, aiming to support risk-based decision-making and data-driven process development. A material library was constructed using a reduced yet diverse set of material attributes (e.g., flowability, particle size, density, cohesion), enabling targeted experimentation and transferability of insights to various materials.
A model for selecting feeding equipment configurations was developed based on feeder emptying curve parameters and the intra-bin variability. The study highlighted the advantages of flat-bottom feeders and the necessity of screw variety for material-specific selection. Key correlations were found between bulk/tapped density and curve parameters, while hopper design and agitator features were shown to mitigate flow issues like ratholing.
Blending process analysis emphasized the role of flow regimes (shear, avalanching, cataracting, fluidized) and their dependence on material properties, blender fill level, and impeller speed. The integration of a sieving step improved blend uniformity by breaking API aggregates. The strategic placement of lubricant addition ports and weir plates was shown to enhance process robustness, particularly for high drug load formulations.
Theoretical assessments using Egermann's equation enabled pre-selection of blend formulations based on drug load and particle size distribution. Steady-state determination for segregation-prone blends was refined using tracer pulse experiments. Impeller rotation direction was found to influence dead mass accumulation, with weir plates offering a better alternative for increasing fill levels.
Pneumatic transport was generally feasible, though limitations were observed with micronized APIs and fine powders. Alternative transport methods were proposed. A scaling approach using geometric and dynamic principles proved effective for well-flowing and cohesive materials under various process conditions.
Overall, this work establishes a systematic understanding of continuous dosing and blending, linking material attributes and process parameters from raw material to final tablet
Expression von Hitzeschockproteinen (Hsp27, 60, 70) und Aquaporinen (AQP1 und 3) in verschiedenen Organsystemen beim Tod durch Unterkühlung
Get PDFDie vorliegende Dissertation untersucht die Expression von Aquaporinen (AQP1 und AQP3) und Hitzeschockproteinen (HSP27, HSP60 und HSP70) in Herz-, Leber- und Nierengewebe von an Hypothermie Verstorbenen im Vergleich zu einer Kontrollgruppe mit anderen Todesursachen. Ziel war es, mögliche spezifische Marker für die forensische Diagnostik von Hypothermie zu identifizieren.
Das Hypothermiekollektiv umfasste 51 Fälle, das Kontrollkollektiv 48 Fälle. Die Gewebeproben wurden immunhistochemisch analysiert, um die Proteinexpression zu quantifizieren und deren Intensität zu bewerten. Die Ergebnisse zeigen organspezifische Expressionsmuster: Im Hypothermiekollektiv wurden AQP1, AQP3, HSP27, HSP60 und HSP70 in Herz- und Lebergewebe häufiger exprimiert als in der Kontrollgruppe. In den Nieren war die Expression von AQP3 und HSP60 im Kontrollkollektiv höher, während AQP1, HSP27 und HSP70 im Hypothermiekollektiv stärker ausgeprägt waren.
Die Studie zeigt, dass die Expression dieser Proteine durch Hypothermie beeinflusst werden kann, jedoch nicht als alleinige Marker für die Todesursache geeignet ist. Zahlreiche Faktoren wie Vorerkrankungen und andere Stressoren können die Expression ebenfalls beeinflussen. Eine fehlende Proteinexpression schließt eine Hypothermie als Todesursache nicht aus.
Die Ergebnisse legen nahe, dass AQP- und HSP-Expression als ergänzende diagnostische Werkzeuge in der forensischen Medizin verwendet werden können, jedoch weiterhin eine gründliche Anamnese und Obduktion erforderlich sind. Zukünftige Studien könnten weitere Proteine oder Isoformen untersuchen, um spezifischere Marker für Hypothermie zu identifizieren
Mapping the Anatomical basis for motor control of a single vibrissa muscle across Rat Brain
No full textHow does the cerebral cortex control a single muscle to orchestrate movement? Rabies virus was injected into the intrinsic muscle that protracts the rat C3 vibrissa. The retrograde transneuronal transport of rabies virus was used to identify the most direct output pathways from the cerebral cortex to a single muscle that moves facial vibrissae.
The results show that the most direct cortical output pathways responsible for control of this muscle originate from almost entire primary motor cortex (M1), vibrissae-related primary somatosensory cortex – barrel cortex(S1), secondary somatosensory (S2)and motor cortex(M2), and insular cortex. Apart from the barrel cortex, all these regions exhibit bilateral organization. Interestingly, M1 contains distinct subregions in both hemispheres that can differentially contribute to the control of contralateral and ipsilateral vibrissa muscles.
For comparison, the rabies virus was also injected into a single forepaw muscle, extensor digitorium communis (EDC). The direct cortical output pathways for forelimb motor control originate majority from contralateral cortical regions that were also represented by the vibrissae, particularly in M1, M2, and S2 and minor overlap in S1. However, output pathways from S1 are topographically organized and remain segregated for forelimb and vibrissae movements. This topological distinction suggests fundamental differences in how cortex integrate information for different muscle groups.
Surprisingly, while infected neurons were observed in the insular cortex for vibrissa control, no neurons were detected in this region for forelimb control. This suggests that its role is specific to facial motor functions. This also highlights that the cortical output system for controlling a single vibrissa muscle is more complex than that for a single forelimb muscle.
In the final part of this study, I also examined the distribution of rabies-infected motoneurons (vMNs) in the facial nucleus (FN) in higher-order brains. I observed a higher number of infected vMNs along with labeling in the contralateral FN, indicating the presence of indirect interhemispheric projections. Additionally, mean size of these vMNs was lower compared to second and third-order brains, indicating potential differences in functional roles or connectivity patterns of these vMNs.
In conclusion, the findings reveal that multiple functionally distinct cortical areas, both within and beyond the primary motor cortex (M1), contribute in parallel to the control of individual muscles. The evidence shows that robustness rabies virus tracing is a powerful tool for studying the anatomical basis of motor control in rats. These insights offer a foundation for further research into the hierarchical and integrative mechanisms underlying motor control in mammals
Aktivierung von pathogenem MCT8 mithilfe von Natriumphenylbutyrat in juvenilen Mäusen
Get PDFKontext: Mutationen im Gen SLC16A2 verursachen die seltene, X-chromosomal vererbte MCT8-Defizienz. Die Erkrankung führt zu einer charakteristischen Kombination von Symptomen einer zentralen Hypothyreose mit schweren Entwicklungsstörungen, neurokognitiven Einschränkungen und globaler muskulärer Hypotonie, sowie Symptomen einer peripheren Hyperthyreose. Natriumphenylbutyrat (NaPB) konnte in Zellkulturmodellen bereits die Expression und Funktion bestimmter pathogener MCT8-Varianten, darunter MCT8P321L, verbessern. Ziel dieser Arbeit war es, die Wirkung von NaPB auf die pathogene Variante MCT8P253L (murines Korrelat von P321L) in vivo zu untersuchen.
Ergebnis: Die postnatale Behandlung von MCT8P253L-Mäusen mit NaPB führte zu einer Verbesserung der hyperthyreoten Stoffwechsellage im Lebergewebe sowie zu einer partiellen Normalisierung der Expression von T3-regulierten Zielgenen im cerebralen Cortex. Eine Gewebe-spezifische Analyse zeigte, dass die Expression von MCT8P253L in Nierengewebe reduziert, im Lebergewebe jedoch erhalten war, womit erstmals die Kontextabhängigkeit der Stabilität von MCT8P253L in vivo bestätigt werden konnte. In primären Astrozyten führte die Behandlung mit NaPB zu einer erhöhten Aufnahme von T3 und T4 durch Induktion von MCT8 und weiteren Transportern. Diese Ergebnisse unterstreichen das therapeutische Potenzial von NaPB zur Stabilisierung funktionell eingeschränkter MCT8-Varianten und zur Behandlung zentraler und peripherer Manifestationen der MCT8-Defizienz. Um das volle Potential und mögliche Nebenwirkungen der Behandlung mit NaPB abschließend zu beurteilen, sind jedoch weitere Versuche notwendig.Context: Mutations in the SLC16A2 gene cause the rare, X-linked disorder known as MCT8-deficiency. The disease is characterized by a distinct combination of symptoms, including central hypothyroidism with severe developmental delays, neurocognitive impairments, and global muscular hypotonia, alongside signs of peripheral hyperthyroidism. Sodium phenylbutyrate (NaPB) has already been shown in cell culture models to improve the expression and function of certain pathogenic MCT8 variants, including MCT8P321L.The aim of this study was to investigate the effect of NaPB on the pathogenic MCT8P253L variant (the murine equivalent of human P321L) in vivo.
Results: Postnatal treatment of MCT8P253L mice with NaPB led to an improvement of the hyperthyroid metabolic state in liver tissue and a partial normalization of the expression of T3-regulated target genes in the cerebral cortex. Tissue-specific analysis revealed a reduced expression of MCT8P253L in kidney tissue, while expression in liver tissue remained preserved, thereby confirming for the first time the context-dependent stability of MCT8P253L in an in vivo model.In primary astrocytes, NaPB treatment enhanced the uptake of T3 and T4 by inducing MCT8 and additional thyroid hormone transporters. These results highlight the therapeutic potential of NaPB for stabilizing functionally impaired MCT8 variants and for addressing both central and peripheral manifestations of MCT8 deficiency. However, further studies are necessary to fully evaluate the therapeutic potential and possible side effects of NaPB treatment
International agri-food trade: country level stability and firms' labor market interactions
Get PDFInternational trade of agri-food products is essential for global food security. However, the trade network has faced numerous challenges at different scales — global, regional, and firm-level. These include recent shocks that have tested the resilience of the trade system, as well as various policy interventions. With a particular focus on trade stability, this thesis comprises four studies that investigate determinants of trade patterns in the agri-food sector. They contribute to the understanding of challenges and benefits for agri-food trade associated with the COVID-19 pandemic, institutional quality, food safety standards, and firms' labor market power.
The first study reveals that during the COVID-19 pandemic, the agri-food trade system has experienced short-term disruptions when pandemic-related restrictions were at their peak. Correlation analyses show that changes in countries' trade values and diversification are associated with policy stringency, people's mobility, and industrial production output.
The second and third study shed light on the impact of countries' institutional quality and standard stringency on agri-food trade stability. Analyzing exports from Sub-Saharan Africa (SSA) to the EU-28 countries, the second study shows that higher levels of exporters' institutional quality and similarity of institutional quality between trading partners facilitate longer trade durations. When distinguishing between different dimensions of institutional quality, the strongest effect arises from exporters' government selection, monitoring, and replacement in SSA. Regarding bilateral similarity, respect for institutions by citizens and state is the most relevant dimension. In the third study, a theory- and literature-based framework shows that stringency and bilateral differences in food safety standards have ambiguous implications for trade stability. The global empirical analysis of agri-food trade reveals that higher importers' stringency in Maximum Residue Levels, an important agri-food standard, and bilateral similarities therein lead to longer and less volatile agri-food trade relations.
Focusing on the food processing sector, the last study analyses the relation of firms' export activities and their labor market power. Employing French firm-level data, the study finds that export participation and higher export intensity are associated with lower labor market power of firms. Reciprocally, higher labor market power of firms decreases export intensities but does not affect export participation. Investigating the relevance of markdown components demonstrates that wage and productivity components matter for both directions of the relationship between labor market power and export activities.Der internationale Handel mit Agrarerzeugnissen und Lebensmitteln ist essenziell für die globale Ernährungssicherheit. Zuletzt wurde das Handelssystem jedoch mit zahlreichen Herausforderungen auf verschiedenen Ebenen — global, regional und auf Unternehmensebene — konfrontiert. Daher werden in dieser Dissertation, mit besonderem Fokus auf die Stabilität von Handelsbeziehungen, die Determinanten des internationalen Agrar- und Lebensmittelhandels anhand von vier Studien analysiert. Die Untersuchungen tragen zum Verständnis jener Dynamiken im internationalen Agrar- und Lebensmittelhandel bei, die mit der COVID-19-Pandemie, der Qualität von Institutionen, Lebensmittelsicherheitsstandards und der Macht von Unternehmen auf dem Arbeitsmarkt verbunden sind.
Die erste Studie zeigt, dass das Agrar- und Lebensmittelhandelssystem während der COVID-19-Pandemie kurzfristige Einbrüche erlebte, insbesondere als pandemiebedingte Einschränkungen ihren Höhepunkt erreichten. Durch Korrelationsanalysen wird deutlich, dass Veränderungen von Handelswerten und -diversifizierung mit der Strenge politischer Maßnahmen, der industriellen Produktionsleistung und den Bewegungsmustern der Bevölkerung zusammenhängen.
Die zweite und dritte Studie beleuchten den Einfluss der Qualität staatlicher Institutionen sowie der Stringenz von Standards auf die Handelsstabilität im Agrar- und Lebensmittelsektor. In der zweiten Studie werden Exporte aus Subsahara-Afrika (SSA) in die EU-28 analysiert. Hierbei zeigt sich, dass eine höhere institutionelle Qualität der Exportländer sowie geringere institutionelle Unterschiede zwischen Handelspartnern zu länger andauernden Handelsbeziehungen führen. Von den verschiedenen Dimensionen institutioneller Qualität hat die Regierungsauswahl, -überwachung und -absetzung in den SSA-Ländern den stärksten Einfluss. Hinsichtlich der bilateralen Unterschiede ist die Achtung von Institutionen durch Bürger und staatliche Organe am relevantesten. Die dritte Studie verdeutlicht zum einen, basierend auf Theorie und Literatur, dass die Stringenz und bilaterale Unterschiede bezüglich Lebensmittelsicherheitsstandards ambivalente Auswirkungen auf die Handelsstabilität haben können. Zusätzlich ergibt eine globale empirische Untersuchung, dass höhere Rückstandshöchstwerte für Substanzen auf Lebensmittel und Futter sowie ähnlichere Werte zwischen Handelspartners zu längeren und weniger volatilen Handelsbeziehungen führen.
Die vierte Studie analysiert den Zusammenhang zwischen Exportaktivitäten lebensmittelverarbeitender Unternehmen und deren Macht auf dem Arbeitsmarkt. Basierend auf französischen Unternehmensdaten ergibt die Studie, dass eine Exportteilnahme und höhere Exportintensität mit einer geringeren Marktmacht der Unternehmen auf dem Arbeitsmarkt verbunden sind. Umgekehrt verringert eine höhere Marktmacht von Unternehmen die Exportintensität, beeinflusst jedoch nicht die Exportteilnahme. Zudem verdeutlicht die Untersuchung, dass Lohn- und Produktivitätskomponenten von Marktmacht für diese wechselseitige Beziehung von Bedeutung sind
Veränderungen des subgingivalen Mikrobioms nach subgingivaler Instrumentierung und 3- oder 7-tägiger Antibiotikagabe bei Parodontitispatienten
Get PDFHintergrund: Adjuvante systemische Antibiotika können die Effekte der subgingivalen Instrumentierung (SI) bei aggressiver Parodontitis verstärken, sind jedoch mit Risiken für Resistenzentwicklung assoziiert. Ziel dieser Arbeit war die vergleichende Analyse zweier Antibiotikaprotokolle hinsichtlich ihrer Wirkung auf das subgingivale Mikrobiom sowie die Etablierung einer Methodik zur Resistomdetektion.
Methoden: In einer randomisierten, kontrollierten Sekundäranalyse wurden 50 systemisch gesunde Patienten (18–38 Jahre, Parodontitis Stadium III/IV, Grad C) nach SI zusätzlich mit Amoxicillin (3 × 500 mg) und Metronidazol (3 × 500 mg) für entweder 3 Tage (Testgruppe) oder 7 Tage (Kontrollgruppe) behandelt. Subgingivale Plaqueproben wurden zu Baseline sowie nach 3, 6 und 12 Monaten entnommen und mittels 16S-rRNA-Metagenomsequenzierung (Illumina MiSeq, QIIME2) hinsichtlich Zusammensetzung, Alpha- und Betadiversität analysiert. Ergänzend wurde ein Resistom-Analyseprotokoll basierend auf Gesamtgenomsequenzierung (Oxford Nanopore Technologies) an Patientenproben und Porphyromonas gingivalis-Kulturen evaluiert.
Ergebnisse: Beide Gruppen zeigten über den Beobachtungszeitraum eine signifikante Diversitätszunahme. Pathogene des roten Komplexes (P. gingivalis, T. forsythia, T. denticola) waren nach Therapie reduziert, während Aggregatibacter actinomycetem-comitans persistierte bzw. zunahm. Zwischen 3- und 7-tägiger Antibiose bestanden keine signifikanten Unterschiede hinsichtlich mikrobieller Diversität oder Zusammensetzung. Rauchen zeigte keinen signifikanten Einfluss. Die Resistomanalyse ermöglichte den Nachweis vereinzelter Resistenzgene (z. B. Polymyxin-B-Resistenz bei P. gingivalis, Fluorchinolon-Resistenz bei Streptococcus oralis), war jedoch durch hohe Kosten, begrenzte Sensitivität und methodische Komplexität limitiert.
Schlussfolgerung: Eine 3-tägige adjuvante Antibiose in Kombination mit SI führt zu vergleichbaren mikrobiologischen Effekten wie eine 7-tägige Therapie. Dies deutet auf ein Potenzial zur Reduktion der Antibiotikadauer ohne Wirksamkeitsverlust hin. Die Etablierung eines Resistom-Analyseprotokolls legt die Grundlage für zukünftige Untersuchungen, ist aktuell jedoch nicht für die Routinediagnostik geeignet
<em>PBRM1</em> loss in clear cell renal cell carcinoma leads to a proangiogenic phenotype via the CXCL5/CXCR2 axis that can be targeted by CXCR2 inhibition
No full textImmune checkpoint blockade (ICB) and anti-angiogenic tyrosine kinase inhibitors (TKI) have substantially improved the outcomes of metastatic clear cell renal cell carcinoma (ccRCC). Nevertheless, the anti-angiogenic TKIs targeting the VEGF/ VEGFR axis result only in temporary antitumor response, and most ccRCCs become ultimately TKI-resistant. Mutations of polybromo-1 (PBRM1) occur in about one-third of ccRCC. It is well known that PBRM1-mutated tumors are highly vascularized. This project aims to dissect the molecular mechanism driving the proangiogenic phenotype of PBRM1-mutated ccRCC. In an unbiased approach, pharmacological inhibition of PBRM1 in ccRCC cell line leads to strong upregulation of the CXCR2 ligands CXCL5 and CXCL6. Accordingly, our TCGA in silico analysis revealed that PBRM1-mutant ccRCC exhibited enhanced CXCL1, CXCL2, CXCL3, and CXCL5 expression; furthermore, patients who had high CXCL5 mRNA expression are associated with worse prognosis in TCGA-KIRC. We established CRISPR-Cas9 induced polyclonal PBRM1-knockouts in the ccRCC cell lines 786O and Caki1. We also identified elevated secretion of CXCL1, CXCL2, CXCL5, CXCL6, and CXCL8, all CXCR2-activating chemokines in PBRM1-loss cell lines. Exposing the cells to pro-inflammatory cytokines (TNFα, and IL-17A) leads to hyper-induction of these chemokines. PBRM1-KO conditioned-media (CM) significantly promoted HUVECs viability and culminated in the enhanced phosphorylation of GSK-3β compared to PBRM1-wild-type CM. The addition of CXCR2 blockade to ccRCC not only suppressed the inhibition of GSK3β signaling, but also the proliferation of HUVECs. The association between PBRM1-deficiency and an enhanced tumor angiogenesis was recapitulated using the spheroid sprouting assay, a three-dimensional (3D) in vitro angiogenic model. Augmented angiogenic sprouting was detected in HUVEC-spheroids which were incubated with supernatant from PBRM1-loss cells. CXCL5 was identified as one of the drivers of the pro-angiogenic phenotype of PBRM1-mutated tumors. Of note, enhanced sprouting capacity of the supernatant of PBRM1-KO ccRCC cell lines can be selectively suppressed by CXCR2 inhibitor and CXLC5 blocking antibody. The therapeutic potential of CXCL5/CXCR2 signaling pathway disruption in ccRCC were shown in the CAM assay, underscoring that targeting CXCL5/CXCR2 axis is a promising approach for ccRCC treatment, specifically in PBRM1-defective ccRCC
Context-aware Deep Learning in Medical Image Analysis
Get PDFDeep Learning (DL) has demonstrated outstanding performance in the area of medical image analysis, with models achieving levels of accuracy that may exceed those of human experts across various applications. This highlights the significant potential of DL-based diagnostic decision support systems to optimize clinical workflows and improve patient outcomes. However, challenges remain that limit the clinical impact and advancements of DL-based systems, such as the need of interpretability or extensive labeled data sets. Since annotation typically requires expert knowledge, generating large-scale annotated data sets presents significant time- and cost constraints. In the following thesis, we address these challenges by incorporating prior contextual information into the DL process, a method known as context-aware DL. Specifically, we focus on two types of contextual information: expert knowledge and prior insights regarding the label quality. The following open research questions are addressed to support the advancement of DL-based decision support systems: 1) Can expert knowledge be leveraged to mitigate current challenges in medical image analysis, and if so, how? 2) Is it possible to utilize contextual information to attain good performance in the multi-label classification of medical image data despite a substantial proportion of missing labels, and if so, how? 3) Is it feasible to integrate contextual information about the label quality to enhance performance when handling data sets with label noise, and if so, how?
Firstly, we integrate expert knowledge regarding the elements of bilateral symmetry of the lung fields into the DL method to automatically detect lung diseases in chest X-ray data. The symmetry-aware architectures and loss function surpass state-of-the-art data-driven DL baselines, enhancing interpretability and data efficiency. To further investigate the potential of expert knowledge as contextual insight, we examine the context-aware analysis of lumbar spine magnetic resonance imaging scans. We demonstrate that contextual information can be integrated through a two-step process. The given work presents an expert knowledge system that utilizes data-driven segmentation masks of the most crucial entities, enabling interpretable diagnostic decision support. These methods emphasize the benefits of context-aware DL based on expert knowledge to address crucial challenges in the medical image analysis field.
Moreover, we focus on the contextual information based on prior insights regarding the label quality to address missing labels or label noise. Proposed novel loss functions achieve high classification performance, surpassing state-of-the-art methods when handling single positive multi-label training for medical images. Additionally, we present a context-aware pre-training strategy to efficiently utilize automatically generated labels, significantly reducing the annotation costs. The context-aware method surpasses purely data-driven training (e.g. not distinguishing between manually and automatically generated labels), highlighting the potential of context-aware training pipelines.
Finally, we introduce a novel context-aware loss function, that achieves remarkable performance even in the presence of label noise. This given context-aware loss enables the abstaining of potentially noisy samples by integrating insights about the expected label noise as a form of regularization. The presented work underscores the significant potential of context-aware DL to mitigate the adverse effects of missing labels or label noise.
In addition to the introduction of novel context-aware DL methods that address the relevant research questions, we tackle further significant shortcomings in the domain of medical image analysis. We evaluate both proposed and state-of-the-art DL methods within this field, with a particular emphasis on German patient cohorts. This work bridges state-of-the-art DL research and the crucial area of medical image analysis, presenting initial investigation of relevant DL methods for the domain. Consequently, our work enhances the assessment of applicable DL methods for real-life medical image use cases, ultimately improving their potential clinical impact.
Overall, this thesis contributes to the advancement of context-aware DL-based diagnosis decision support systems, aiming to alleviate the workload of medical professionals in their daily practice while enhancing patient outcomes
How legitimate are urban climate planning processes? : A comparative assessment of Accra, Ahmedabad, Bonn and São Paulo
Get PDFUrban climate action plans (UCAPs) guide cities in identifying key climate risks and in addressing climate change. Designed to guide urban transformation over decades through near-term and long-term actions reducing emissions and/or adapting to the consequences of climate change, UCAPs are intended to have significant impacts. Despite their significance for urban climate governance, the procedural quality of how UCAPs are created remains under-analysed. By analysing UCAPs of four cities from different regions of the world - Accra (Ghana), Bonn (Germany), São Paulo (Brazil), and Ahmedabad (India) - we unpack the quality of UCAP creation processes in terms of their legitimacy including whether and how key stakeholders were involved in shaping the plan. Drawing on 72 semi-structured interviews with actors involved in the plan-creation process and complemented by document analysis, this study conceptualises UCAP creation phases and assesses its quality using the framework of input, throughput, and output legitimacy. In terms of key actors, this study highlights the crucial role city networks played in designing and funding UCAP creation processes. Significant differences in UCAP legitimacy with regards to levels of co-production, transparency, accessibility, and substantive participation across the case studies are shown. Based on these findings this study provides actionable insights for the creation of legitimate and impactful UCAPs to promote just and equitable urban transformations
Imaging of osmiophilic excipients using electron microscopy approaches
No full textDrug delivery systems usually contain excipients composed of light elements such as carbon and nitrogen, oxygen. These elements in particular make up the majority of active ingredients and excipients resulting in no or minor differences in electron density. However, the materials can have different affinities towards contrast-enhancing agents, so that it is possible to differentiate between the various materials on the basis of the changes in electron density after contrasting. Cellular delivery of nanomedicines using drug delivery systems face similar challenges. Common excipients used for cellular delivery are composed of light elements and are thus nearly indistinguishable from the surrounding biological material.
Resulting from this, the main objective of this work is the visualization of pharmaceutical excipients in drug delivery systems and cells by electron microscopy using contrasting techniques. To achieve this, contrast enhancement strategies using osmium tetroxide as well as ruthenium tetroxide are explored. Contrast enhancement strategies are of particular interest for the technique of focused ion beam scanning electron microscopy (FIB-SEM), which has attracted great interest in recent years as a novel tool for the characterization of drug delivery systems. Neither contrast enhanced drug delivery systems nor imaging of cellular ultrastructure after nanoparticle treatment by electron microscopy are commonly imaged in the field of pharmaceutics.
With these approaches, it was possible to visualize the localization of a self-emulsifying drug delivery system (SEDDS) within the porous silicate carrier Florite R using scanning electron microscopy (SEM) and FIB-SEM. SEDDS-loaded Florite R-containing tablets prepared by compaction and vacuum compression molding (VCM) were also imaged using this approach.
In addition to the electron microscopic characterization of drug delivery systems, the uptake of lipid nano carriers consisting of unsaturated lipid excipients after staining with osmium tetroxide was visualized using SEM and scanning transmission electron microscopy (STEM). The lipid nano carriers were rapidly digested as indicated by Lipid droplet formation. Nevertheless, the lipid nano carriers could successfully be visualized within the endolysosomal system especially after chloroquine co-treatment.
These investigations will benefit our understanding of ultrastructural features of drug delivery systems and cellular trafficking of drug delivery systems