Poly(2-oxazoline)s: synthesis, self-assembly and biomedical applications

Poly(2-oxazolin)e (POx) stellen aufgrund ihrer Möglichkeit maßgeschneidert hergestellt zu werden, interessante Kandidaten für die biomedizinische Anwendung, insbesondere für den Gen- und Wirkstofftransport, dar. In der vorliegenden Arbeit wurden 2-Oxazoline und Oxazolidinimine synthetisiert, charakterisiert und polymerisiert. Hierbei ergaben sich in Abhängigkeit von der Reaktionskonstanten der Monomere zufällig, gradiell oder blockähnlich verteilte Polymere. Wasserlösliche nicht-ionische POx konnten zur Stabilisierung hydrophober Nanopartikel genutzt werden. Wasserlösliche, aminhaltige POx sowie aminhaltige, pH-responsive Nanostrukturen bestehend aus amphiphilien Block-Copolymeren wurden für den Gentransport genutzt. Dabei konnten die wasserlöslichen POx nicht zu einer Transfektion der Zellen führen, während die Nanostrukturen Transfektionseffizienzen aufwiesen, wie vergleichbar mit der Positivkontrolle Poly(ethylenimin) waren. Für den Wirkstofftransport wurden wasserlösliche POx genutzt. Hierbei wurden niedermolekulare Wirkstoffe oder Proteine kovalent an die Polymere gebunden. Es konnte gezeigt werden, dass die Wirkstoffe eine vergleichbare oder erhöhte Aktivität besitzen wie Wirkstoffe, welche nicht an ein Polymer gebunden wurden. Des Weiteren konnte im Falle des Doxorubicins, eines Zytostatikums, gezeigt werden, dass die Verwendung von kernvernetzten POx Nanogelen, an die der Wirkstoff über eine Iminbindung reversibel kovalent gebunden wurde, zu einer erhöhten Überlebensrate von Versuchstieren im in vivo Experiment führte

Molecular and rheological characterization of sodium hyaluronate (HA) and equine synovial fluid

Sodium hyaluronate (HA) is a polysaccharide found in all parts of the body Although it performs important functions in the eye, the coagulation process and other parts of the body, its contribution to synovial fluid is particularly important. As the major component of synovial fluid, HA is responsible for the viscoelastic properties important in joint lubrication and cartilage protection. In this thesis, molecular and rheological characterization techniques were used to study; i) commercial HA materials and HA synovial fluid supplements; ii) equine synovial fluid from different joints of both live and deceased horses; iii) equine synovial fluid from a clinical study of intraarticular HA supplementation in the hock joints of a group of six horses. Commercial HA materials and HA intended for intra-articular, intravenous and oral supplementation were studied using size exclusion chromatography combined with inline multi-angle laser light scattering (SEC-MALLS), dilute solution capillary viscometry to obtain intrinsic viscosity ([η]), and steady shear and dynamic oscillatory shear rheology. The molecular weight range of the HA samples was 2.88x10⁵ to 1.96x10⁶ Da. The molecular weight and intrinsic viscosity were correlated and a Mark-Houwink-Sakurada equation for HA in phosphate buffer solution (PBS) was found to be [η] = 0.17 Mw⁰`⁶⁸. The "a" value of 0.68 indicates HA behaves as a random coil in PBS which is consistent with values reported in literature. Zero shear viscosities of the samples at a concentration of 2.5 mg/ml ranged from approximately 0.06 to 0.5 Pa-s and were found to have a nearly linear relationship with the product of molecular weight and concentration (η ∝ cMw¹.⁰⁸). All samples exhibited both viscous and elastic properties in the dynamic oscillatory shear tests. The correlation between molecular weight and rheological properties of pure HA indicates that these techniques may be used in the future to characterize HA materials and possibly to discern the connection between molecular properties of HA and their lubrication properties in synovial fluid. The techniques used to characterize pure sodium hyaluronate samples were then applied to equine synovial fluid from a number of live and deceased horses (euthanized for reasons unrelated to this study) in an attempt to elucidate the role of HA in joint lubrication. The concentration and molecular weight of the HA-protein complex in synovial fluid was measured using SECMALLS. Steady shear and dynamic oscillatory shear tests were also performed on synovial fluid samples. The investigation of the properties of synovial fluid in normal equine joints reported in this thesis is the beginning of an attempt to establish baseline values for comparison with diseased joints. The molecular weight of HA in synovial fluid ranged from 1.5x10⁶ to 6.5x10⁶ Dalton (Da) and concentration ranged from 0.11 to 0.84 mg/mI, both are in the range of values reported in literature. The steady shear viscosity of synovial fluid samples ranged from about 0.001 to 1 Pa-s, with slight upturns at low shear rates in some samples, indicative of aggregation. The molecular characterization is difficult due to the complexity of the fluid. Although each sample exhibits unique rheological properties, at this time changes in viscosity or elasticity cannot be correlated to changes in either molecular weight or concentration of HA. Finally, a preliminary study of the intra-articular injection of HA was completed using six healthy horses and rheological characterization of synovial fluid from tarsocrural hock joints. The horses were divided into three groups: the experimental group (2 ml of Hyvisc, an HA supplement, in each hock); the positive control group (2 ml of Lactated Ringers Solution (LRS) in each hock); and the negative control group (no treatment). The horses received the above treatments after aspiration of synovial fluid for the samples that were treated as the baseline value for each hock joint. Synovial fluid samples were also taken one and two weeks after treatment. Cytology, including total protein and nucleated cell counts, was performed to monitor the health of the joints throughout the study. Rheological properties of synovial fluid in the experimental group increased one week after treatment compared to the control groups. This could be due to exogenous HA remaining in the joint after treatment, indicating that it takes longer than one week for exogenous HA to be cleared from the joint. Two weeks after treatment all test groups returned to the pre-treatment state. This was most likely due to the fact that the joints were aspirated one week after treatment, negating both treatment and non-treatment effects by the second week of the study

Transcriptional responses of Burkholderia cenocepacia to polymyxin B in isogenic strains with diverse polymyxin B resistance phenotypes

<p>Abstract</p> <p>Background</p> <p><it>Burkholderia cenocepacia </it>is a Gram-negative opportunistic pathogen displaying high resistance to antimicrobial peptides and polymyxins. We identified mechanisms of resistance by analyzing transcriptional changes to polymyxin B treatment in three isogenic <it>B. cenocepacia </it>strains with diverse polymyxin B resistance phenotypes: the polymyxin B-resistant parental strain K56-2, a polymyxin B-sensitive K56-2 mutant strain with heptoseless lipopolysaccharide (LPS) (RSF34), and a derivative of RSF34 (RSF34 4000B) isolated through multiple rounds of selection in polymyxin B that despite having a heptoseless LPS is highly polymyxin B-resistant.</p> <p>Results</p> <p>A heptoseless LPS mutant of <it>B. cenocepacia </it>was passaged through multiple rounds of selection to regain high levels of polymyxin B-resistance. This process resulted in various phenotypic changes in the isolate that could contribute to polymyxin B resistance and are consistent with LPS-independent changes in the outer membrane. The transcriptional response of three <it>B. cenocepacia </it>strains to subinhibitory concentrations of polymyxin B was analyzed using microarray analysis and validated by quantitative Real Time-PCR. There were numerous baseline changes in expression between the three strains in the absence of polymyxin B. In both K56-2 and RSF34, similar transcriptional changes upon treatment with polymyxin B were found and included upregulation of various genes that may be involved in polymyxin B resistance and downregulation of genes required for the synthesis and operation of flagella. This last result was validated phenotypically as both swimming and swarming motility were impaired in the presence of polymyxin B. RSF34 4000B had altered the expression in a larger number of genes upon treatment with polymyxin B than either K56-2 or RSF34, but the relative fold-changes in expression were lower.</p> <p>Conclusions</p> <p>It is possible to generate polymyxin B-resistant isolates from polymyxin B-sensitive mutant strains of <it>B. cenocepacia</it>, likely due to the multifactorial nature of polymyxin B resistance of this bacterium. Microarray analysis showed that <it>B. cenocepacia </it>mounts multiple transcriptional responses following exposure to polymyxin B. Polymyxin B-regulated genes identified in this study may be required for polymyxin B resistance, which must be tested experimentally. Exposure to polymyxin B also decreases expression of flagellar genes resulting in reduced swimming and swarming motility.</p

Accelerated spreading of inviscid droplets prompted by the yielding of strongly elastic interfacial films

The complexity associated with droplets spreading on surfaces has attracted significant interest for several decades. Sustained activity results from the many natural and manufactured systems that are reliant on droplet-substrate interactions and spreading. Interfacial shear rheology and its influence on the dynamics of droplet spreading has to date received little attention. In the current study, saponin β-aescin was used as an interfacial shear rheology modifier, partitioning at the air-water interface to form a strongly elastic interface (G’/G” ∼ 6) within 1 min aging. The droplet spreading dynamics of Newtonian (water, 5 wt% ethanol, 0.0015 wt% N-dodecyl β-D-glucopyranoside) and non-Newtonian (xanthan gum) fluids were shown to proceed with a time-dependent power-law dependence of ∼0.50 and ∼0.10 (Tanner’s law) in the inertial and viscous regimes of spreading, respectively. However, water droplets stabilized by saponin β-aescin were shown to accelerate droplet spreading in the inertial regime with a depreciating time-dependent power-law of 1.05 and 0.61, eventually exhibiting a power-law dependence of ∼ 0.10 in the viscous regime of spreading. The accelerated rate of spreading is attributed to the potential energy as the interfacial film yields as well as relaxation of the crumpled interfacial film during spreading. Even though the strongly elastic film ruptures to promote droplet spreading, interfacial elasticity is retained enhancing the dampening of droplet oscillations following detachment from the dispensing capillary

archiv.gut.normieren: Das Projekt GND4C am Landesarchiv Baden-Württemberg

Vortrag beim 90. Deutschen Archivtag am 28. September 2023 in Bielefeld INHALT: - GND4C-Phase 1: Aller Anfang ist schwer… : Ausgangslage - GND4C-Phase 2: …aber am Ende wird (fast) alles gut : Ergebniss