From anionic polymerization in continuous flow to macromolecular architectures and stimuli-responsive surfaces

The thesis can be divided in four parts and summarized as follows:(i) The investigation and development of a continuous flow synthesis procedure affording end-functional polymers by anionic polymerization and subsequent termination in one reaction step and on a multigram scale was carried out. Furthermore, the implementation of not only a single hydroxyl but multiple orthogonal functionalities at the chain terminus was achieved by utilizing individually designed, functional epoxide-based end-capping reagents.(ii) In an additional step, the respective polymers were used as macroinitiators to prepare in-chain functionalized block copolymers and star polymers bearing intriguing novel structural and material properties. Thus, the second part of this thesis presents the utilization of end-functional polymers as precursors for the synthesis of amphiphilic complex and in some cases unprecedented macromolecular architectures, such as miktoarm star polymers based on poly(vinyl pyridine), poly(vinyl ferrocene) and PEO.(iii) Based on these structures, the third part of this thesis represents a detailed investigation of the preparation of stimuli-responsive ultrathin polymer films, using amphiphilic junction point-reactive block copolymers. The single functionality at the block interface can be employed as anchor group for the covalent attachment on surfaces. Furthermore, the change of surface properties was studied by applying different external stimuli.(iv) An additional topic related to the oxyanionic polymerizations carried out in the context of this thesis was the investigation of viscoelastic properties of different hyperbranched polyethers, inspired by the recent and intense research activities in the field of biomedical applications of multi-functional hyperbranched materials.

Stimuli-responsive materials for self-healing in corrosion protection

The corrosion of metallic materials is a crucial issue on an economical and ecological scale. Corrosion protection becomes then necessarily needed. The main focus of the thesis is to develop stimuli-responsive nanocontainers for self-healing in corrosion protection. A nanocontainer is efficient if distinct payloads can be selectively released via different stimuli because unwanted and unspecific release can be avoided. For anti-corrosion, the wanted nanocontainer is the one able to release its self-healing agents or corrosion inhibitors upon change of pH- or/and redox-potential due to the variation of these two signals at the corroded sites. Conducting polymers such as polyaniline (PANI) were chosen for building the shell of capsules due to their important characteristics of being both pH- and redox responsive.

Synthesis and application of stimuli responsive tunable systems based on physical interactions

Novel single step synthetic procedure for hydrophobically modified alkali soluble latexes (HASE) via a miniemulsion-analogous method is presented. This facile method simplifies the copolymerization of the monomers with basically “opposite” character in terms of their hydrophilic/hydrophobic nature, which represent one of the main challenges in water based systems. Considered systems do not represent classical miniemulsions due to a high content of water soluble monomers. However, the polymerization mechanism was found to be rather similar to miniemulsion polymerization process.rnThe influence of the different factors on the system stability has been investigated. The copolymerization behavior studies typically showed strong composition drifts during copolymerization. It was found that the copolymer composition drift can be suppressed via changing the initial monomer ratio.rnThe neutralization behavior of the obtained HASE systems was investigated via potentiometric titration. The rheological behavior of the obtained systems as a function of the different parameters, such as pH, composition (ultrahydrophobe content) and additive type and content has also been investigated.rnDetailed investigation of the storage and loss moduli, damping factor and the crossover frequencies of the samples showed that at the initial stages of the neutralization the systems show microgel-like behavior.rnThe dependence of the rheological properties on the content and the type of the ultrahydrophobe showed that the tuning of the mechanical properties can be easily achieved via minor (few percent) but significant changes in the content of the latter. Besides, changing the hydrophobicity of the ultrahydrophobe via increasing the carbon chain length represents another simple method for achieving the same results.rnThe influence of amphiphilic additives (especially alcohols) on the rheological behavior of the obtained systems has been studied. An analogy was made between micellation of surfactants and the formation of hydrophobic domains between hydrophobic groups of the polymer side chain.rnDilution induced viscosity reduction was investigated in different systems, without or with different amounts or types of the amphiphilic additive. Possibility of the controlled response to dilution was explored. It was concluded that the sensitivity towards dilution can be reduced, and in extreme cases even the increase of the dynamic modulus can be observed, which is of high importance for the setting behavior of the adhesive material.rnIn the last part of this work, the adhesive behavior of the obtained HASE systems was investigated on different substrates (polypropylene and glass) for the standard labeling paper. Wet tack and setting behavior was studied and the trends for possible applications have been evaluated.rnThe novel synthetic procedure, investigation of rheological properties and the possibility of the tuning via additives, investigated in this work create a firm background for the development of the HASE based adhesives as well as rheology modifiers with vast variety of possible applications due to ease of tuning the mechanical and rheological properties of the systems.

SphK1 regulates proinflammatory responses associated with endotoxin and polymicrobial sepsis

During sepsis, activation of phagocytes leads to the overproduction of proinflammatory cytokines, causing systemic inflammation. Despite substantial information regarding the underlying molecular mechanisms that lead to sepsis, several elements in the pathway remain to be elucidated. We found that the enzyme sphingosine kinase 1 (SphK1) is up-regulated in stimulated human phagocytes and in peritoneal phagocytes of patients with severe sepsis. Blockade of SphK1 inhibited phagocyte production of endotoxin-induced proinflammatory cytokines. We observed protection against sepsis in mice treated with a specific SphK1 inhibitor that was enhanced by treatment with a broad-spectrum antibiotic. These results demonstrated a critical role for SphK1 in endotoxin signaling and sepsis-induced inflammatory responses and suggest that inhibition of SphK1 is a potential therapy for septic shock.

Fluorescent-magnetic hybrid nanoparticles induce a dose-dependent increase in proinflammatory response in lung cells in vitro correlated with intracellular localization

Iron-platinum nanoparticles embedded in a poly(methacrylic acid) (PMA) polymer shell and fluorescently labeled with the dye ATTO 590 (FePt-PMA-ATTO-2%) are investigated in terms of their intracellular localization in lung cells and potential to induce a proinflammatory response dependent on concentration and incubation time. A gold core coated with the same polymer shell (Au-PMA-ATTO-2%) is also included. Using laser scanning and electron microscopy techniques, it is shown that the FePt-PMA-ATTO-2% particles penetrate all three types of cell investigated but to a higher extent in macrophages and dendritic cells than epithelial cells. In both cell types of the defense system but not in epithelial cells, a particle-dose-dependent increase of the cytokine tumor necrosis factor alpha (TNFalpha) is found. By comparing the different nanoparticles and the mere polymer shell, it is shown that the cores combined with the shells are responsible for the induction of proinflammatory effects and not the shells alone. It is concluded that the uptake behavior and the proinflammatory response upon particle exposure are dependent on the time, cell type, and cell culture.

Self-efficacy buffers the relationship between dementia caregiving stress and circulating concentrations of the proinflammatory cytokine interleukin-6

the proinflammatory cytokine interleukin (IL)-6 has been linked with health morbidity, particularly risk for cardiovascular disease (CVD). The purpose of this study was to investigate the potential protective role of coping self-efficacy on the relationship between caregiving stress and circulating concentrations of IL-6.

Numerical assessment on the effective mechanical stimuli for matrix-associated metabolism in chondrocyte-seeded constructs

The self-regeneration capacity of articular cartilage is limited, due to its avascular and aneural nature. Loaded explants and cell cultures demonstrated that chondrocyte metabolism can be regulated via physiologic loading. However, the explicit ranges of mechanical stimuli that correspond to favourable metabolic response associated with extracellular matrix (ECM) synthesis are elusive. Unsystematic protocols lacking this knowledge produce inconsistent results. This study aims to determine the intrinsic ranges of physical stimuli that increase ECM synthesis and simultaneously inhibit nitric oxide (NO) production in chondrocyte-agarose constructs, by numerically re-evaluating the experiments performed by Tsuang et al. (2008). Twelve loading patterns were simulated with poro-elastic finite element models in ABAQUS. Pressure on solid matrix, von Mises stress, maximum principle stress and pore pressure were selected as intrinsic mechanical stimuli. Their development rates and magnitudes at the steady state of cyclic loading were calculated with MATLAB at the construct level. Concurrent increase in glycosaminoglycan and collagen was observed at 2300 Pa pressure and 40 Pa/s pressure rate. Between 0-1500 Pa and 0-40 Pa/s, NO production was consistently positive with respect to controls, whereas ECM synthesis was negative in the same range. A linear correlation was found between pressure rate and NO production (R = 0.77). Stress states identified in this study are generic and could be used to develop predictive algorithms for matrix production in agarose-chondrocyte constructs of arbitrary shape, size and agarose concentration. They could also be helpful to increase the efficacy of loading protocols for avascular tissue engineering. Copyright (c) 2010 John Wiley \& Sons, Ltd.

Factor analysis of responses to thermal, electrical, and mechanical painful stimuli supports the importance of multi-modal pain assessment

During the last decade, a multi-modal approach has been established in human experimental pain research for assessing pain thresholds and responses to various experimental pain modalities. Studies have concluded that differences in responses to pain stimuli are mainly related to variation between individuals rather than variation in response to different stimulus modalities. In a factor analysis of 272 consecutive volunteers (137 men and 135 women) who underwent tests with different experimental pain modalities, it was determined whether responses to different pain modalities represent distinct individual uncorrelated dimensions of pain perception. Volunteers underwent single painful electrical stimulation, repeated painful electrical stimulation (temporal summation), test for reflex receptive field, pressure pain stimulation, heat pain stimulation, cold pain stimulation, and a cold pressor test (ice water test). Five distinct factors were found representing responses to 5 distinct experimental pain modalities: pressure, heat, cold, electrical stimulation, and reflex-receptive fields. Each of the factors explained approximately 8% to 35% of the observed variance, and the 5 factors cumulatively explained 94% of the variance. The correlation between the 5 factors was near null (median ρ=0.00, range -0.03 to 0.05), with 95% confidence intervals for pairwise correlations between 2 factors excluding any relevant correlation. Results were almost similar for analyses stratified according to gender and age. Responses to different experimental pain modalities represent different specific dimensions and should be assessed in combination in future pharmacological and clinical studies to represent the complexity of nociception and pain experience.

Effects of Echinaforce® treatment on ex vivo-stimulated blood cells

The herb Echinacea purpurea, also called purple coneflower, is regarded as an immune modulator. This study examined changes in cytokine production in blood samples from 30 volunteers before and during 8-day oral administration with an ethanolic extract of fresh Echinacea purpurea (Echinaforce(®)). Daily blood samples were ex vivo stimulated by LPS/SEB or Zymosan and analysed for a series of cytokines and haematological and metabolic parameters. Treatment reduced the proinflammatory mediators TNF-α and IL-1β by up to 24% (p<0.05) and increased anti-inflammatory IL-10 levels by 13% (p<0.05) in comparison to baseline. This demonstrated a substantial overall anti-inflammatory effect of Echinaforce(®) for the whole group (n=28). Chemokines MCP-1 and IL-8 were upregulated by 15% in samples from subjects treated with Echinaforce(®) (p<0.05). An analysis of a subgroup of volunteers who showed low pre-treatment levels of the cytokines MCP-1, IL-8, IL-10 or IFN-γ (n=8) showed significant stimulation of these factors upon Echinaforce(®) treatment (30-49% increases; p<0.05), whereas the levels in subjects with higher pre-treatment levels remained unaffected. We chose the term "adapted immune-modulation" to describe this observation. Volunteers who reported high stress levels (n=7) and more than 2 colds per year experienced a significant transient increase in IFN-γ upon Echinaforce(®) treatment (>50%). Subjects with low cortisol levels (n=11) showed significant down-regulation of the acute-phase proteins IL1-β, IL-6, IL-12 and TNF-α by Echinaforce(®) (range, 13-25%), while subjects with higher cortisol levels showed no such down-regulation. This is the first ex vivo study to demonstrate adapted immune-modulation by an Echinacea preparation. While Echinaforce(®) did not affect leukocyte counts, we speculate that the underlying therapeutic mechanism is based on differential multi-level modulation of the responses of the different types of leukocytes. Echinaforce(®) thus regulates the production of chemokines and cytokines according to current immune status, such as responsiveness to exogenous stimuli, susceptibility to viral infection and exposure to stress.

Validity of multi-fiber muscle velocity recovery cycles recorded at a single site using submaximal stimuli

To examine the validity of multi-fiber muscle velocity recovery cycles (VRCs) recorded by direct muscle stimulation with submaximal stimuli.

Applying chemical stimuli on feathers to reduce feather pecking in laying hens

Recent studies have shown that spraying a distasteful substance (quinine) on a bird's feather cover reduced short-term feather pecking. The present experiment evaluated if other substances offer similar or better protection against feather pecking.;One hundred and twenty birds were divided into 12 groups of 10 birds each. Over a period of 10 days the birds' response to 10 feathers coated with one of the 11 distasteful substances was observed and recorded. Feathers were soaked in a 1% garlic solution, 1% almond oil, 1% clove oil, 1% clove solution, quinine sulphate solution in four concentrations (0.1%, 1%, 2%, 4%), 0.6 mol magnesium chloride solution, anti-peck spray or an angostura solution. The control group received uncoated feathers. The number of feathers plucked, rejected or eaten was counted 60 min after presenting the feathers. All substances reduced feather plucking (p < 0.0001) and consumption (p < 0.0001) significantly, compared to uncoated feathers. Quinine concentrations of 2% and 4% were most effective. This study was the first to investigate the aversive potential of different substances to deter feather peckers from the feathers of other birds. The findings may be useful in the development of spraying devices to prevent feather pecking when other management tools fail. (c) 2011 Elsevier B.V. All rights reserved.

Functional, structural and molecular plasticity of mammalian skeletal muscle in response to exercise stimuli

Biological systems have acquired effective adaptive strategies to cope with physiological challenges and to maximize biochemical processes under imposed constraints. Striated muscle tissue demonstrates a remarkable malleability and can adjust its metabolic and contractile makeup in response to alterations in functional demands. Activity-dependent muscle plasticity therefore represents a unique model to investigate the regulatory machinery underlying phenotypic adaptations in a fully differentiated tissue. Adjustments in form and function of mammalian muscle have so far been characterized at a descriptive level, and several major themes have evolved. These imply that mechanical, metabolic and neuronal perturbations in recruited muscle groups relay to the specific processes being activated by the complex physiological stimulus of exercise. The important relationship between the phenotypic stimuli and consequent muscular modifications is reflected by coordinated differences at the transcript level that match structural and functional adjustments in the new training steady state. Permanent alterations of gene expression thus represent a major strategy for the integration of phenotypic stimuli into remodeling of muscle makeup. A unifying theory on the molecular mechanism that connects the single exercise stimulus to the multi-faceted adjustments made after the repeated impact of the muscular stress remains elusive. Recently, master switches have been recognized that sense and transduce the individual physical and chemical perturbations induced by physiological challenges via signaling cascades to downstream gene expression events. Molecular observations on signaling systems also extend the long-known evidence for desensitization of the muscle response to endurance exercise after the repeated impact of the stimulus that occurs with training. Integrative approaches involving the manipulation of single factors and the systematic monitoring of downstream effects at multiple levels would appear to be the ultimate method for pinpointing the mechanism of muscle remodeling. The identification of the basic relationships underlying the malleability of muscle tissue is likely to be of relevance for our understanding of compensatory processes in other tissues, species and organisms.