Conjugated Polymer-Based Biomaterials Through Controlled Self-Assembly

Synthetic polymeric materials have gained significant use as biological materials (biomaterials) in biomedical and pharmaceutical applications. As a result, a demand for well-defined polymers with tunable properties has emerged. The synthetic versatility of polymeric biomaterials allows the opportunity to understand the structure-property relationship of materials and their cellular interactions. A novel class of polymeric biomaterials are conjugated polymers (CPs), which possess desirable physicochemical and excellent photophysical properties, including inherent fluorescence. The synthetic versatility of CPs allows easy modification of the conjugated backbone to tune emission and side chain structures to adjust biocompatibility through increased water solubility, controlled biodegradability, and incorporation of targeting units. The aim of this dissertation is to better understand conjugated polymer nanoparticle (CPN) structure and self-assembly in an aqueous environment, and how those structural features affect cellular interactions to establish a structure-function relationship. This work presents the fabrication of several different CPNs for cancer cell targeting and labelling, and differentiation of biologically important molecules. Core−shell nanoparticles were prepared using a semi-flexible cationic CPN complexed with hyaluronic acid (HA), a polyanion. The resulting CPNs exhibited high cancer cell specificity with low adsorption to normal cells, as a result of HA’s affinity towards overexpressed receptors on cancer cell surface. A systematic investigation on the aggregation properties of CPNs that vary by side chain and backbone structures in response to different biologically important anionic polysaccharides in a complex biological medium was conducted. Mitochondria-specific CPNs were fabricated from a semi-flexible CPN modified with the mitochondrial-targeting triphenylphosphonium (TPP) group. The subcellular localization and cellular toxicity were dependent on backbone flexibility, hydrophilicity, and molecular weight. Dual-targeting CPNs grafted with folic acid (FA) side chains and complexed with hyaluronic acid (HA) were fabricated for improved uptake and bioimaging of cancer cells. The work presented here shows how modifications to CPN backbone and side chain structures modulate their cellular interactions. The physicochemical and biophysical properties of CPNs affect biocompatibility and understanding those properties will lead to the development of novel CP-based biomaterials

Characterization of PhPRP1, an extracellular arabinogalactan protein from Petunia hybrida pistils

An extracellular arabinogalactan protein, PhPRP1, was identified from Petunia hybrida pistils on the basis of nucleotide sequence similarity with NaTTS from Nicotiana alata and TTS-1 from Nicotiana tabacum. PhPRP1 exhibits 83% and 81% nucleotide identity with NaTTS and TTS-1 cDNAs, respectively. The amino acid sequence deduced from the cDNA predicts a 27.4 kDa polypeptide backbone with a 25 amino acid signal sequence. Sequence alignments of PhPRP1 and the TTS proteins reveals two hypervariable regions, including a proline-rich domain with noncontiguous KPP repeats. A short, highly-conserved histidinerich domain separates the two hypervariable regions. The C-terminal segment of the protein shows significant sequence similarity to the Pollen Ole e 1 superfamily of arabinogalactan proteins, with perfect conservation of the six cysteine residues characteristic of the family. This multidomain architecture--especially the histidine-rich conserved domain and the proline-rich hypervariable region with KPP motifs--is a distinctive feature of TTS proteins and their orthologs in Petunia hybrida (PhPRP1) and Capsicum annuum (CaPRP1). An antibody specific to NaTTS detected PhPRP1, and purified PhPRP1 also reacted with β-glucosyl Yariv reagent, a dye that is diagnostic for arabinogalactans. BLAST searches identified sequences highly similar to PhPRP1 in expressed sequence tag (EST) libraries prepared from Petunia axillaris pistils and P. axillaris primary roots, which suggests that PhPRP1 is derived from the P. axillaris progenitor of P. hybrida, and that the PRP/TTS family of arabinogalactan proteins is not unique to pistil tissues. Phylogenetic analyses cluster the vegetative tissue ESTs with the pistil-expressed PRPs/TTS proteins at polytomies, indicating little differentiation among them. The gene geneology of PRPs/TTS proteins is mostly concordant with recent interpretations of the phylogeny of the Solanaceae based on concatenation of chloroplast and nuclear genes, with some differences in topology depending on the evolutionary models employed to construct the gene tree. As key mediators of pollenpistil interactions, PRP/TTS proteins may have an important role in generating reproductive barriers between sister species

Development of Partial Ontogenic Resistance to Powdery Mildew in Hop Cones and Its Management Implications

Knowledge of processes leading to crop damage is central to devising rational approaches to disease management. Multiple experiments established that infection of hop cones by Podosphaera macularis was most severe if inoculation occurred within 15 to 21 days after bloom. This period of infection was associated with the most pronounced reductions in alpha acids, cone color, and accelerated maturation of cones. Susceptibility of cones to powdery mildew decreased progressively after the transition from bloom to cone development, although complete immunity to the disease failed to develop. Maturation of cone tissues was associated with multiple significant affects on the pathogen manifested as reduced germination of conidia, diminished frequency of penetration of bracts, lengthening of the latent period, and decreased sporulation. Cones challenged with P. macularis in juvenile developmental stages also led to greater frequency of colonization by a complex of saprophytic, secondary fungi. Since no developmental stage of cones was immune to powdery mildew, the incidence of powdery mildew continued to increase over time and exceeded 86% by late summer. In field experiments with a moderately susceptible cultivar, the incidence of cones with powdery mildew was statistically similar when fungicide applications were made season-long or targeted only to the juvenile stages of cone development. These studies establish that partial ontogenic resistance develops in hop cones and may influence multiple phases of the infection process and pathogen reproduction. The results further reinforce the concept that the efficacy of a fungicide program may depend largely on timing of a small number of sprays during a relatively brief period of cone development. However in practice, targeting fungicide and other management tactics to periods of enhanced juvenile susceptibility may be complicated by a high degree of asynchrony in cone development and other factors that are situation-dependent

Pre- and Postinfection Activity of Fungicides in Control of Hop Downy Mildew

Optimum timing and use of fungicides for disease control are improved by an understanding of the characteristics of fungicide physical mode of action. Greenhouse and field experiments were conducted to quantify and model the duration of pre- and postinfection activity of fungicides most commonly used for control of hop downy mildew (caused by Pseudoperonospora humuli). In greenhouse experiments, control of downy mildew on leaves was similar among fungicides tested when applied preventatively but varied depending on both the fungicide and the timing of application postinfection. Disease control decreased as applications of copper were made later after inoculation. In contrast, cymoxanil, trifloxystrobin, and dimethomorph reduced disease with similar efficacy when applied 48 h after inoculation compared with preventative applications of these fungicides. When fungicides were applied 72 h after inoculation, only dimethomorph reduced the sporulating leaf area similarly to preinoculation application timing. Adaxial chlorosis, necrosis, and water soaking of inoculated leaves, indicative of infection by P. humuli, were more severe when plants were treated with cymoxanil, trifloxystrobin, and dimethomorph 48 to 72 h after inoculation, even though sporulation was suppressed. Trifloxystrobin and dimethomorph applied 72 h after inoculation suppressed formation of sporangia on sporangiophores as compared with all other treatments. In field studies, dimethomorph, fosetyl-Al, and trifloxystrobin suppressed development of shoots with systemic downy mildew to the greatest extent when applied near the timing of inoculation, although the duration of preventative and postinfection activity varied among the fungicides. There was a small reduction in efficacy of disease control when fosetyl-Al was applied 6 to 7 days after inoculation as compared with protective applications. Trifloxystrobin had 4 to 5 days of preinfection activity and limited postinfection activity. Dimethomorph had the longest duration of protective activity. Percent disease control was reduced progressively with increasing time between inoculation and application of dimethomorph. These findings provide guidance to the use of fungicides when applications are timed with forecasted or post hoc disease hazard warnings, as well as guidance on tank-mixes of fungicides that may be suitable both for resistance management considerations and extending intervals between applications

Impact of CARDIOrespiratory FITness on Arrhythmia Recurrence in Obese Individuals With Atrial Fibrillation The CARDIO-FIT Study

AbstractBackgroundObesity begets atrial fibrillation (AF). Although cardiorespiratory fitness is protective against incident AF in obese individuals, its effect on AF recurrence or the benefit of cardiorespiratory fitness gain is unknown.ObjectivesThis study sought to evaluate the role of cardiorespiratory fitness and the incremental benefit of cardiorespiratory fitness improvement on rhythm control in obese individuals with AF.MethodsOf 1,415 consecutive patients with AF, 825 had a body mass index ≥27 kg/m2 and were offered risk factor management and participation in a tailored exercise program. After exclusions, 308 patients were included in the analysis. Patients underwent exercise stress testing to determine peak metabolic equivalents (METs). To determine a dose response, cardiorespiratory fitness was categorized as: low (<85%), adequate (86% to 100%), and high (>100%). Impact of cardiorespiratory fitness gain was ascertained by the objective gain in fitness at final follow-up (≥2 METs vs. <2 METs). AF rhythm control was determined using 7-day Holter monitoring and AF severity scale questionnaire.ResultsThere were no differences in baseline characteristics or follow-up duration between the groups defined by cardiorespiratory fitness. Arrhythmia-free survival with and without rhythm control strategies was greatest in patients with high cardiorespiratory fitness compared to adequate or low cardiorespiratory fitness (p < 0.001 for both). AF burden and symptom severity decreased significantly in the group with cardiorespiratory fitness gain ≥2 METs as compared to <2 METs group (p < 0.001 for all). Arrhythmia-free survival with and without rhythm control strategies was greatest in those with METs gain ≥2 compared to those with METs gain <2 in cardiorespiratory fitness (p < 0.001 for both).ConclusionsCardiorespiratory fitness predicts arrhythmia recurrence in obese individuals with symptomatic AF. Improvement in cardiorespiratory fitness augments the beneficial effects of weight loss. (Evaluating the Impact of a Weight Loss on the Burden of Atrial Fibrillation [AF] in Obese Patients; ACTRN12614001123639

Characterizing the cancer genome in lung adenocarcinoma

Somatic alterations in cellular DNA underlie almost all human cancers(1). The prospect of targeted therapies(2) and the development of high-resolution, genome-wide approaches(3-8) are now spurring systematic efforts to characterize cancer genomes. Here we report a large-scale project to characterize copy-number alterations in primary lung adenocarcinomas. By analysis of a large collection of tumours ( n = 371) using dense single nucleotide polymorphism arrays, we identify a total of 57 significantly recurrent events. We find that 26 of 39 autosomal chromosome arms show consistent large-scale copy-number gain or loss, of which only a handful have been linked to a specific gene. We also identify 31 recurrent focal events, including 24 amplifications and 7 homozygous deletions. Only six of these focal events are currently associated with known mutations in lung carcinomas. The most common event, amplification of chromosome 14q13.3, is found in similar to 12% of samples. On the basis of genomic and functional analyses, we identify NKX2-1 ( NK2 homeobox 1, also called TITF1), which lies in the minimal 14q13.3 amplification interval and encodes a lineage-specific transcription factor, as a novel candidate proto-oncogene involved in a significant fraction of lung adenocarcinomas. More generally, our results indicate that many of the genes that are involved in lung adenocarcinoma remain to be discovered.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/62944/1/nature06358.pd

College student adaptation to childhood adversity: a model of stress and resilience

2010 Summer.Includes bibliographic references (pages 58-70).Covers not scanned.Print version deaccessioned 2022.A model of resilience was tested in a college sample of 672 students. Data were collected on the association of negative life events and college adjustment. The influence of Neuroticism, coping style, and social/emotional resources was also studied. Structural equation modeling procedures were used to analyze these data, and a moderating effect of gender was hypothesized. Results provided support for the hypothesized model and indicated that stress, Neuroticism, Engagement coping, and social/emotional resources have important implications for adjustment. Specifically, it was found that the experience of negative life events was positively associated with elevated levels of Neuroticism for both men and women. Neuroticism, in turn, was associated with Disengagement coping as well as a decrease in social/emotional resource availability. Neuroticism was also negatively associated with college adjustment, though Neuroticism was somewhat more strongly related to college adjustment for females. Coping styles were also related to the availability of social/emotional resources, such that the use of Engagement coping was associated with greater resource availability. Furthermore, results indicated the presence of a positive relationship between Engagement coping and college adjustment, whereas no relationship was observed between college adjustment and Disengagement coping. Surprisingly, results suggested the presence of no relationship between /emotional resources and adjustment to college. Additional analyses examined social the relationship between life events and adjustment, and it was found that those disproportionately experiencing more negative life events reported poorer college adjustment. Possible explanations for the observed findings are considered. Implications for practice are discussed

Caveolae-Mediated Endocytosis Of Conjugated Polymer Nanoparticles

Understanding the cellular entry pathways of synthetic biomaterials is highly important to improve overall labeling and delivery efficiency. Herein, cellular entry mechanisms of conjugated polymer nanoparticles (CPNs) are presented. CPNs are intrinsic fluorescent materials used for various biological applications. While CPNs cause no toxicity, decreased CPN uptake is observed from cancer cells pretreated with genistein, which is an inhibitor of caveolae-mediated endocytosis (CvME). CvME is further confirmed by high co-localization with caveolin-1 proteins found in the caveolae and caveosomes. Excellent photophysical properties, non-toxicity, and non-destructive delivery pathways support that CPNs are promising multifunctional carriers minimizing degradation of contents during delivery. A detailed cellular entry mechanism of conjugated polymer nanoparticles (CPNs) is presented. Cancer cells pretreated with an inhibitor of caveolae-mediated endocytosis (CvME) exhibit decreased CPN uptake. High co-localization with caveolin-1 proteins found in the caveolae and caveosomes further confirms CvME of CPNs. Non-toxicity and non-destructive delivery pathways support that CPNs are promising carriers, minimizing content degradation during delivery. © 2013

Synthesising wave attenuation for seagrass: drag coefficient as a unifying indicator

An estimated 100 million people inhabit coastal areas at risk from flooding and erosion due to climate change. Seagrass meadows, like other coastal ecosystems, attenuate waves. Due to inconsistencies in how wave attenuation is measured results cannot be directly compared. We synthesised data from laboratory and field experiments of seagrass-wave attenuation by converting measurements to drag coefficients (C). Drag coefficients varied from 0.02–5.12 with C¯ = 0.74 for studies conducted in turbulent flow in non-storm conditions. A statistical model suggested that seagrass species affects C although the exact mechanism remains unclear. A wave model using the estimated C¯ as an input parameter demonstrated that wave attenuation increased with meadow length, shoot density, shoot width and canopy height. Findings can be used to estimate wave attenuation by seagrass, in any given set of conditions

GentDavidBotanyPlantPathPrePostinfectionActivitySup.1.pdf

Optimum timing and use of fungicides for disease control are improved by an understanding of the characteristics of fungicide physical mode of action. Greenhouse and field experiments were conducted to quantify and model the duration of pre- and postinfection activity of fungicides most commonly used for control of hop downy mildew (caused by Pseudoperonospora humuli). In greenhouse experiments, control of downy mildew on leaves was similar among fungicides tested when applied preventatively but varied depending on both the fungicide and the timing of application postinfection. Disease control decreased as applications of copper were made later after inoculation. In contrast, cymoxanil, trifloxystrobin, and dimethomorph reduced disease with similar efficacy when applied 48 h after inoculation compared with preventative applications of these fungicides. When fungicides were applied 72 h after inoculation, only dimethomorph reduced the sporulating leaf area similarly to preinoculation application timing. Adaxial chlorosis, necrosis, and water soaking of inoculated leaves, indicative of infection by P. humuli, were more severe when plants were treated with cymoxanil, trifloxystrobin, and dimethomorph 48 to 72 h after inoculation, even though sporulation was suppressed. Trifloxystrobin and dimethomorph applied 72 h after inoculation suppressed formation of sporangia on sporangiophores as compared with all other treatments. In field studies, dimethomorph, fosetyl-Al, and trifloxystrobin suppressed development of shoots with systemic downy mildew to the greatest extent when applied near the timing of inoculation, although the duration of preventative and postinfection activity varied among the fungicides. There was a small reduction in efficacy of disease control when fosetyl-Al was applied 6 to 7 days after inoculation as compared with protective applications. Trifloxystrobin had 4 to 5 days of preinfection activity and limited postinfection activity. Dimethomorph had the longest duration of protective activity. Percent disease control was reduced progressively with increasing time between inoculation and application of dimethomorph. These findings provide guidance to the use of fungicides when applications are timed with forecasted or post hoc disease hazard warnings, as well as guidance on tank-mixes of fungicides that may be suitable both for resistance management considerations and extending intervals between applications