INMdok (Leibniz Institute for New Materials)
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Nanomechanics of self-assembled DNA building blocks
Get PDFDNA has become a powerful platform to design functional nanodevices. DNA nanodevices are often composed of self-assembled DNA building blocks that differ significantly from the structure of native DNA. In this study, we present Flow Force Microscopy as a massively parallel approach to study the nanomechanics of DNA self-assemblies on the single-molecular level. The high-throughput experiments performed in a simple microfluidic channel enable statistically meaningful studies with nanometer scale precision in a time frame of several minutes. A surprisingly high flexibility was observed for a typical construct used in DNA origami, reflected in a persistence length of 10.2 nm, a factor of five smaller than for native DNA. The enhanced flexibility is attributed to the discontinuous backbone of DNA self-assemblies that facilitate base pair opening by thermal fluctuations at the end of hybridized oligomers. We believe that the results will contribute to the fundamental understanding of DNA nanomechanics and help to improve the design of DNA nanodevices with applications in biological analysis and clinical research
Fabrication of physically crosslinked hydrogel materials with good mechanical properties
Get PDFSoft gels serve promising features for various applications. For this aim, several strategies to form crosslinked networks have been implemented. Mostly, they suffer from non-dynamicity, which leads to limitations of swelling and good mechanical properties. In this thesis, polymer entanglements are used as the main crosslinking method, and enabled good mechanical properties with high swelling (∼98 wt%). Entanglements are weak physical interactions, which are result of arbitrary passing polymer chains. They are believed to be too weak to build networks for hydrogelation. The crosslinking is based on in-situ entanglement cluster formation inside polymer nanogels. Following that, stimulus-responsive behavior is supplied into the physical entanglement hydrogels (PEH). When nanogels had been switched to thermoresponsive PNIPAM, sliding of chain entanglements can be regulated. PEH does not undergo clear shrinkage, even it is stiffened. In addition, organohydrogel with anisotropic behaviors is investigated in this study. Anisotropy is common in nature, and provides different features in materials. Organohydrogels are able to consist of binary phases of hydrophilic and oleophilic molecules. Herein, anisotropic organohydrogel fabrication via polymerization induced phase separation is developed. The gel can show different properties, including stiffness, viscoelasticity and surface roughness.Weiche Gele bieten vielversprechende Eigenschaften für verschiedene Anwendungen. Zu diesem Zweck wurden verschiedene Strategien zur Bildung vernetzter Netzwerke implementiert. Meistens leiden sie unter Nichtdynamik, was zu Einschränkungen der Quellung und guten mechanischen Eigenschaften führt. In dieser Arbeit werden Polymerverschränkungen als Hauptvernetzungsmethode verwendet und ermöglichen gute mechanische Eigenschaften bei hoher Quellung (98 Gew.-%). Verwicklungen sind schwache physikalische Wechselwirkungen, die auf willkürlich vorbeiziehende Polymerketten zurückzuführen sind. Es wird angenommen, dass sie zu schwach sind, um Netzwerke für die Hydrogelierung aufzubauen. Die Vernetzung basiert auf der Bildung von In-situ-Verschränkungsclustern in Polymer-Nanogelen. Anschließend wird den physikalischen Verschränkungshydrogelen (PEH) ein auf Reize ansprechendes Verhalten zugeführt. Wenn Nanogele auf thermoresponsives PNIPAM umgestellt wurden, kann das Gleiten von Kettenverschränkungen reguliert werden. PEH schrumpft nicht deutlich, auch wenn es versteift ist. Zusätzlich wird in dieser Studie Organohydrogel mit anisotropem Verhalten untersucht. Anisotropie ist in der Natur üblich und bietet verschiedene Eigenschaften in Materialien. Organohydrogele können aus binären Phasen hydrophiler und oleophiler Moleküle bestehen. Hierin wird eine anisotrope Organohydrogelherstellung durch polymerisationsinduzierte Phasentrennung entwickelt. Das Gel kann verschiedene Eigenschaften aufweisen, einschließlich Steifheit, Viskoelastizität und Oberflächenrauheit
Cylindrical Microparticles Composed of Mesoporous Silica Nanoparticles for the Targeted Delivery of a Small Molecule and a Macromolecular Drug to the Lungs: Exemplified with Curcumin and siRNA
Get PDFThe transport of macromolecular drugs such as oligonucleotides into the lungs has become increasingly relevant in recent years due to their high potency. However, the chemical structure of this group of drugs poses a hurdle to their delivery, caused by the negative charge, membrane impermeability and instability. For example, siRNA to reduce tumour necrosis factor alpha (TNF- α) secretion to reduce inflammatory signals has been successfully delivered by inhalation. In order to increase the effect of the treatment, a co-transport of another anti-inflammatory ingredient was applied. Combining curcumin-loaded mesoporous silica nanoparticles in nanostructured cylindrical microparticles stabilized by the layer-by-layer technique using polyanionic siRNA against TNF-α was used for demonstration. This system showed aerodynamic properties suited for lung deposition (mass median aerodynamic diameter of 2.85 ± 0.44 µm). Furthermore, these inhalable carriers showed no acute in vitro toxicity tested in both alveolar epithelial cells and macrophages up to 48 h incubation. Ultimately, TNF- α release was significantly reduced by the particles, showing an improved activity co-delivering both drugs using such a drug-delivery system for specific inhibition of TNF-α in the lung
Scanning electron microscopy preparation of the cellular actin cortex: A quantitative comparison between critical point drying and hexamethyldisilazane drying
Get PDFThe cellular cortex is an approximately 200-nm-thick actin network that lies just beneath the cell membrane. It is responsible for the mechanical properties of cells, and as such, it is involved in many cellular processes, including cell migration and cellular interactions with the environment. To develop a clear view of this dense structure, high-resolution imaging is essential. As one such technique, electron microscopy, involves complex sample preparation procedures. The final drying of these samples has significant influence on potential artifacts, like cell shrinkage and the formation of artifactual holes in the actin cortex. In this study, we compared the three most used final sample drying procedures: critical-point drying (CPD), CPD with lens tissue (CPD-LT), and hexamethyldisilazane drying. We show that both hexamethyldisilazane and CPD-LT lead to fewer artifactual mesh holes within the actin cortex than CPD. Moreover, CPD-LT leads to significant reduction in cell height compared to hexamethyldisilazane and CPD. We conclude that the final drying procedure should be chosen according to the reduction in cell height, and so CPD-LT, or according to the spatial separation of the single layers of the actin cortex, and so hexamethyldisilazane
Enhancing Dry Adhesion of Polymeric Micropatterns by Electric Fields
Get PDFMicropatterned dry adhesives rely mainly on van der Waals interactions. In this paper, we explore the adhesion strength increase that can be achieved by superimposing an electrostatic field through interdigitated subsurface electrodes. Micropatterns were produced by replica molding in silicone. The adhesion forces were characterized systematically by means of experiments and numerical modeling. The force increased with the square of the applied voltage for electric fields up to 800 V. For larger fields, a less-than-quadratic scaling was observed, which is likely due to the small, field-dependent electrical conductivity of the materials involved. The additional adhesion force was found to be up to twice of the field-free adhesion. The results suggest an alternative method for the controlled handling of fragile or miniaturized objects
PhysioSkin: Rapid Fabrication of Skin-Conformal Physiological Interfaces
Get PDFAdvances in rapid prototyping platforms have made physiological sensing accessible to a wide audience. However, off-the-shelf electrodes commonly used for capturing biosignals are typically thick, non-conformal and do not support customization. We present PhysioSkin, a rapid, do-it-yourself prototyping method for fabricating custom multi-modal physiological sensors, using commercial materials and a commodity desktop inkjet printer. It realizes ultrathin skin-conformal patches (~1μm) and interactive textiles that capture sEMG, EDA and ECG signals. It further supports fabricating devices with custom levels of thickness and stretchability. We present detailed fabrication explorations on multiple substrate materials, functional inks and skin adhesive materials. Informed from the literature, we also provide design recommendations for each of the modalities. Evaluation results show that the sensor patches achieve a high signal-to-noise ratio. Example applications demonstrate the functionality and versatility of our approach for prototyping a next generation of physiological devices that intimately couple with the human body
Influence of core size and capping ligand of gold nanoparticles on the desorption/ionization efficiency of small biomolecules in AP-SALDI-MS
Get PDFGold nanoparticles (AuNP) are frequently used in surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) for analysis of biomolecules because they exhibit suitable thermal and chemical properties as well as strong surface plasmonic effects. Moreover, the structures of AuNP can be controlled by well-established synthesis protocols. This was important in the present work, which studied the influence of the nanoparticles’ structures on atmospheric pressure (AP)-SALDI-MS performance. A series of AuNP with different core sizes and capping ligands were investigated, to examine the desorption/ionization efficiency (DIE) under AP-SALDI conditions. The results showed that both the AuNP core size as well as the nature of the surface ligand had a strong influence on DIE. DIE increased with the size of the AuNP and the hydrophobicity of the ligands. Chemical interactions between ligand and analytes also influenced DIE. Moreover, we discovered that removing the organic ligands from the deposited AuNP substrate layer by simple laser irradiation prior to LDI further amplified DIE values. The optimized AuNP were successfully used to analyze a wide arrange of different low molecular weight biomolecules as well as a crude pig brain extract, which readily demonstrated the ability of the technique to detect a wide range of lipid species within highly complex samples
Synthese, Charakterisierung und optoelektronische Anwendungen von Nb-TiO2
Get PDFIn dieser Arbeit wurde eine Synthese zur Herstellung von Ti-Nb-Oxid-Nanopartikeln für unterschiedliche Verhältnisse zwischen Ti und Nb entwickelt. Es entstehen mikrometer-große kugelförmige Agglomerate mit einer hierarchisch aufgebauten Kern-Schale-Struktur, deren Kern Nb-arm im Vergleich zur Schale ist. Die Partikel wurden später für (opto-)elektronische Anwendungen getestet. Als erstes wurde der Einsatz als transparent leitfähiges Oxid (TCO) untersucht. Die deagglomerierten Partikel wurden zu Tinten verarbeitet und daraus Schichten auf Glas hergestellt. Der Zusatz der Vorstufen, die auch für die Synthese verwendeten wurden, wirkte sich im Vergleich zu Acrylaten als Binder positiv auf den Widerstand aus. Im Gegensatz zu anderen TCOs zeigt Nb:TiO2 eine photokatalytisch Aktivität, wel- che bei der Nachbehandlung berücksichtigt werden muss. Weiterhin wurden die elektrischen Eigenschaften von Pellets untersucht, die aus dem Pulver gepresst und nachbehandelt wurden. Der Widerstand der Pellets hängt maßgeblich von den Temperaturen und Gasen während der Nachbehandlung sowie den erhaltenen Strukturen und Phasen ab. Der geringste Widerstand wurde bei Nb-Gehalten um 20 und 66 at% und Temperaturen über 750◦C erzielt. Als weitere Anwendung wurden die Mikrokugeln für Photoanoden von farbstoffsensibilisierten Solarzellen mit zwei unterschiedlichen Farbstoffen verwendet. Der maximale Wirkungsgrad lag bei 4,1 % und 8,0 % für Eosin Y und N719.In this work, a synthesis for Ti-Nb-oxide-nanoparticles with various Nb-Ti-ratios was developed. The synthesis resulted in microsized spherical agglomerates with hierarchical core-shell-structures where the shell was Nb-rich compared to the core. The particles were subsequently tested in (opto-)electronic applications. First, the application as transparent conductive oxides was investigated. The particles were deagglomerated to produce inks which were coated onto glass substrates. Compared to coatings with an acrylate binder, the resistivity decreased by adding the precursors used in the synthesis of the particles. During the post treatment of coatings, the photocatalytic activity of Nb:TiO2 had to be considered. Furthermore, the electrical properties of pellets pressed from the powders and post-treated were analyzed. The resistivity depended significantly on the temperatures and gases during post-treatment, as well as the resulting structures and phases within the pellet. Temperatures of more than 750◦C and Nb contents of around 20 or 66 at% yielded the lowest resistivities. Additionally, the microspheres were tested as photoanodes of dye-sensitized solar cells with two different dyes. The cells reached efficiencies of up to 4,1 % and 8,0 % for Eosin Y and N719
Tofacitinib loaded squalenyl nanoparticles for targeted follicular delivery in inflammatory skin diseases
Get PDFTofacitinib (TFB), a Janus kinase inhibitor, has shown excellent success off-label in treating various dermatological diseases, especially alopecia areata (AA). However, TFB’s safe and targeted delivery into hair follicles (HFs) is highly desirable due to its systemic adverse effects. Nanoparticles (NPs) can enhance targeted follicular drug delivery and minimize interfollicular permeation and thereby reduce systemic drug exposure. In this study, we report a facile method to assemble the stable and uniform 240 nm TFB loaded squalenyl derivative (SqD) nanoparticles (TFB SqD NPs) in aqueous solution, which allowed an excellent loading capacity (LC) of 20%. The SqD NPs showed an enhanced TFB delivery into HFs compared to the aqueous formulations of plain drug in an ex vivo pig ear model. Furthermore, the therapeutic efficacy of the TFB SqD NPs was studied in a mouse model of allergic dermatitis by ear swelling reduction and compared to TFB dissolved in a non-aqueous mixture of acetone and DMSO (7:1 v/v). Whereas such formulation would not be acceptable for use in the clinic, the TFB SqD NPs dispersed in water illustrated a better reduction in inflammatory effects than plain TFB’s aqueous formulation, implying both encouraging good in vivo efficacy and safety. These findings support the potential of TFB SqD NPs for developing a long-term topical therapy of AA
Targeted delivery of functionalized PLGA nanoparticles to macrophages by complexation with the yeast Saccharomyces cerevisiae
Get PDFAbstract Nanoparticles (NPs) are able to deliver a variety of substances into eukaryotic cells. However, their usage is often hampered by a lack of specificity, leading to the undesired uptake of NPs by virtually all cell types. In contrast to this, yeast is known to be specifically taken up into immune cells after entering the body. Therefore, we investigated the interaction of biodegradable surface-modified poly (lactic-co-glycolic acid) (PLGA) particles with yeast cells to overcome the unspecificity of the particulate carriers. Cells of different Saccharomyces cerevisiae strains were characterized regarding their interaction with PLGA-NPs under isotonic and hypotonic conditions. The particles were shown to efficiently interact with yeast cells leading to stable NP/yeast-complexes allowing to associate or even internalize compounds. Notably, applying those complexes to a co-culture model of HeLa cells and macrophages, the macrophages were specifically targeted. This novel nano-in-micro carrier system suggests itself as a promising tool for the delivery of biologically active agents into phagocytic cells combining specificity and efficiency. This article is protected by copyright. All rights reserved