No description available.

Polycyclic aromatic hydrocarbons (PAHs) are a group of ubiquitous environmental contaminants with two or more aromatic rings and originating from different emission sources. They are extremely toxic, carcinogenic and mutagenic to human, animals and plants. Consequently, the need to expand economical and practical remediation technologies for PAH contaminated sites is evident. In this study, the effect of biotic and abiotic factors on degradation of PAH was studied. The degradation was studied on the key model PAH (phenanthrene, anthracene, fluoranthene and pyrene) in J. Arthur Bower’s top soil. The hypothesis for this study was that roadside soil would contain PAH degrading bacteria; pH would influence the microbial degradation of PAH, chemical oxidation of PAH would be as efficient as microbial breakdown of PAH and mobilising agents, would move PAH throughout soil, potentially making the PAH more available for biodegradation. The greatest degradations were found for the lowest molecular weight PAH, phenanthrene and anthracene; whilst lowest degradation was observed for higher molecular weight PAH, fluoranthene and pyrene. Twelve bacteria genera were isolated and identified by biochemical and molecular techniques from the roadside soil with the four PAHs as the sole carbon source. However, potentially new PAH biodegrader bacteria species and a novel were found in this study, which was not reported in the literature. The effect of pH between 5.0 and 8.0 at half pH intervals on biodegradation of the four PAHs and on bacterial populations in the soil over 32 days was monitored. The greatest population of bacteria and greatest biodegradation for the four PAHs was found at pH of 7.5. It is likely that the general increase in population was also linked with greater metabolic activities of bacteria at basic pHs which assists pollutant biodegradation. Although there is high pollutant mobility at low pHs, the biodegradation was limited due to reduced microbial activity. High pHs resulted in greater PAH biodegradation suggesting that pH manipulation by liming may be an effective way of stimulating biodegradation of PAH. The effect of potassium permanganate on oxidation of the four PAHs in the soil was examined. Studies in this thesis, indicated that potassium permanganate had a significant (p<0.05) effect on oxidation of the four PAHs at pH 7.5 over 35 days. However in comparison to biodegradation, chemical oxidation has significantly (p<0.05) less effect. Finally, the effect of Tween 20 only on translocation and biodegradation of the four PAHs at pH 7.5 over 35 days was examined. Studies indicated that Tween 20 had significantly (p<0.05) enhanced translocation of the four PAHs in the sterile soil. Moreover, the greatest biodegradation was found in the soil inoculated with only the roadside soil microorganisms but without Tween 20. This suggested that Tween 20 had a significant (p<0.05) inhibitory effect on the roadside soil microorganisms and therefore less microorganism were grown in the soil containing Tween 20. This indicated that Tween 20 was translocated PAH, but inhibited breakdown. This study indicated microbial biodegradation was the most effective technique for removing of the PAH from contaminated soil, which was cost effective and easier to perform in comparison to the other two techniques. Microbial biodegradation could be improved by adjusting pH through liming if soil was acid.

Résumé français manquant / Scientific background: GAGs mimetics properties on regenerative process.Glycosaminoglycans (GAGs) are sulfated polysaccharides actually considered as major structural components of the extracellular matrix as well as regulators of cells functions during homeostatic and pathological processes. These GAGs activities are based on their ability to interact with heparin binding growth-factors (HBGF), chemokines and enzymes, to protect them from proteolytic degradation and to potentialyze their interaction with cell surface specific receptors and/or other components of the ECM. GAGs are characterized by their extensive structural diversity, based on the number and location of sulfate or acetylate groups, that would determine specific biological interactions.As comparative tool to study the relationship between the complexity of GAGs chemical structures and their biological functions, we used synthetic GAGs mimetics, derivate from a polymer of dextran and functionalized with carboxylate, sulfate and/or acetate groups. They are structurally and functionally related to natural heparan sulfates. These compounds improved both the rate and quality of regenerative process in numerous animal models of injury after topical treatment.Our hypothesize is that specific HS cooperative interactions with HBGF and ECM compounds could influence both therapeutic progenitors and stem cells properties by compartmentalizing them to specific microenvironment niches, and protecting them against deleterious signals. Such abilities to modulate stem cell biology could be a new way to explain and to take advantage of regenerative properties of these compounds. The principal aim of this work was to demonstrate the effects of GAGs mimetics on Mesenchymal Stem Cells (MSC) properties for application in bone repair. GAGs mimetics as new potentializing agents of mesenchymal stem cells propertiesDuring osteogenesis, a controlled expression of functional HS is required to interact and regulate the activity of growth promoting and osteogenic differentiation factors. However effects of GAGs on MSC properties remain to be analyzed. We focus on two GAGs mimetics leader molecules [OTR4131] and [OTR4120], with distinct chemical characteristics, since sulfated mimetic [OTR4120] was previously shown to stimulate bone repair in vivo. We demonstrate that its acetylated and sulfated counterpart [OTR4131] enhances proliferation, whereas [OTR4120] clearly stimulates migration and osteogenic differentiation properties of rat MSC in vitro, that could explain its bone regenerative effect in vivo. This indicates that GAGs mimetics would be of great interest for potential application in therapy, since according to their structural signature they could modulate specific activities of progenitors and stem cells, and represent an alternative to exogenous growth factor treatments. New matricial strategy for bone repair associating GAGs mimetics to biomaterials and human MSCCell based therapy associated to biomaterials for repair of bone defects are promising but not enough efficient. We proposed to develop matricial strategy, associating efficient micro-environment molecules such as GAGs mimetics, to optimize cell therapeutic approaches. First we validated that GAGs mimetics are effective on human MSC proliferation, migration and differentiation properties in vitro. We demonstrated that colonization efficiency of hydroxyapatite/β-tricalcium phosphate biomaterial scaffolds by human MSC was improved when scaffolds are functionalized with GAGs mimetics in vitro. Finally osteoformation in vivo was evaluated after ectopic transplantation of functionalized and/or cellularized biomaterials in nude mice: few effects were observed on bone formation, whereas osteoclastogenesis and vascularization were clearly modulated by GAGs mimetics immobilized. GAGs mimetics as new mobilizing agents of stem cells...