4 research outputs found

    Attachment of Therapeutic and Imaging Agents to Magnetotactic Bacteria Acting as Self-Propelled Bio-Carriers for Cancer Treatment

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    RÉSUMÉ Malgré les progrès de la médecine moderne, les traitements anticancéreux actuels n’arrivent toujours pas à vaincre le cancer. Seulement une fraction des doses de médicaments administrées parvient à la tumeur en raison d’un ciblage non spécifique, de barrières physiologiques au niveau du système vasculaire ainsi que de l’élimination immédiate de médicaments par le système immunitaire. Des dosages fréquents de médicaments deviennent nécessaires afin de surmonter ces obstacles, entraînant une toxicité systémique, des effets secondaires et un échec thérapeutique. De plus, les systèmes actuels d’imagerie médicale sont incapables de produire des images de haute qualité des structures tumorales pour les diagnostiques et les traitements. Ceci est dû aux restrictions de la résolution spatiale et de l’incapacité des agents de contraste à pénétrer dans les zones tumorales afin de générer un signal suffisamment intense. Le développement de nouveaux agents thérapeutiques ainsi que de nouvelles techniques de ciblage thérapeutique sont donc requis afin d’améliorer l’efficacité des traitements actuels. Pour ce projet de recherche doctorale, l'attachement de charges utiles à la surface de bactéries magnétotactiques flagellées Magnetococcus Marinus MC-1 (BMT) a été mise en place pour transporter de façon ciblée une quantité optimale de médicaments profondément dans les zones tumorales. Ces bio-robots autopropulsés de dimensions adéquates sont équipés d’un système de propulsion dirigeable, d’un système de navigation, et de capacités sensorielles. Divers types de complexes BMT ont été fabriquées en attachant aux BMT (i) des liposomes vides (BMT-LP), (ii) des liposomes contenant un agent anticancéreux SN38 (BMT-LSC), et (iii) des nanoparticules superparamagnétiques de magnétite (BMT-S200). L’efficacité de l'attachement des charges et du comportement des bactéries soumises à un champ magnétique directionnel ont été étudiés. Par la suite, la capacité des complexes BMT à naviguer le long d’une trajectoire prédéterminée, à infiltrer profondément l'espace interstitiel, et à cibler des zones tumorales inaccessibles, ont été étudiés dans un modèle animal soumis à un champ magnétique externe. Pour parvenir à des complexes BMT aptes à transporter suffisamment de produits pharmaceutiques et de s’accumuler préférentiellement dans les régions affectées, il faut assurer un attachement solide et stable qui ne compromet pas la motilité des BMT.----------ABSTRACT Despite the substantial achievements of modern medicine, current medical therapies cannot eradicate cancer. Due to nonspecific targeting, the multiple physiological barriers that blood-borne agents must encounter, and the rapid sequestration of drugs by the immune system, a suboptimal fraction of the total injected dose reaches the intended target. These obstacles necessitate frequent dosing to compensate therapeutic effects, resulting in systemic toxicity, undesirable side effects, and treatment failure. In addition, existing medical imaging modalities struggle to provide high quality clinical images of tumor structures for treatment purposes due to limitations in spatial resolution and lack of penetration of contrast agents into tumoral regions to induce sufficient signal intensity. To address these issues, the development of new therapeutic agents alongside improved strategies for targeting therapy with the ability to control their fate is required. The attachment of payloads to the flagellated Magnetococcus Marinus MC-1 magnetotactic bacteria (MTB) to directly transport optimal quantities of pharmaceutical agents to regions located deep in tumors is what has been proposed during the accomplishment of this PhD project. These engineered self-propelled bio-robots with an appropriate dimension are equipped with steerable propulsion, navigation system, and onboard sensory capabilities. MTB complexes were fabricated by attaching the MTB to (i) empty liposomes (MTB-LP), (ii) SN38 anticancer drug encapsulated in liposomes (MTB-LSC), and (iii) 200 nm superparamagnetic magnetite nanoparticles (MTB-S200). The attachment efficacy and magnetic response behavior from the influence of a directional magnetic field of loaded bacteria with therapeutic or imaging agents were studied. Subsequently, results showed that the attachment method was suitable to allow MC-1 MTB to transport therapeutic and imaging agents along a planned trajectory prior to penetrate deep through the interstitial space in order to reach the hypoxic regions of a tumor in an animal model. To achieve MTB complexes capable of carrying sufficient pharmaceutical agents and accumulating preferentially at disease sites, the attachment must be strong and stable without compromising the natural motility of MTB. The MTB-LP were prepared by direct covalent attachment of functionalized liposomes to the amine groups naturally presented on the surface of MTB using carbodiimide (EDC/NHS) chemistry

    African Handbook of Climate Change Adaptation

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    This open access book discusses current thinking and presents the main issues and challenges associated with climate change in Africa. It introduces evidences from studies and projects which show how climate change adaptation is being - and may continue to be successfully implemented in African countries. Thanks to its scope and wide range of themes surrounding climate change, the ambition is that this book will be a lead publication on the topic, which may be regularly updated and hence capture further works. Climate change is a major global challenge. However, some geographical regions are more severly affected than others. One of these regions is the African continent. Due to a combination of unfavourable socio-economic and meteorological conditions, African countries are particularly vulnerable to climate change and its impacts. The recently released IPCC special report "Global Warming of 1.5º C" outlines the fact that keeping global warming by the level of 1.5º C is possible, but also suggested that an increase by 2º C could lead to crises with crops (agriculture fed by rain could drop by 50% in some African countries by 2020) and livestock production, could damage water supplies and pose an additonal threat to coastal areas. The 5th Assessment Report produced by IPCC predicts that wheat may disappear from Africa by 2080, and that maize— a staple—will fall significantly in southern Africa. Also, arid and semi-arid lands are likely to increase by up to 8%, with severe ramifications for livelihoods, poverty eradication and meeting the SDGs. Pursuing appropriate adaptation strategies is thus vital, in order to address the current and future challenges posed by a changing climate. It is against this background that the "African Handbook of Climate Change Adaptation" is being published. It contains papers prepared by scholars, representatives from social movements, practitioners and members of governmental agencies, undertaking research and/or executing climate change projects in Africa, and working with communities across the African continent. Encompassing over 100 contribtions from across Africa, it is the most comprehensive publication on climate change adaptation in Africa ever produced

    Triple Helix as a Strategic Tool to Fast-Track Climate Change Adaptation in Rural Kenya: Case Study of Marsabit County

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    AbstractThe lack of affordable, clean, and reliable energy in Africa's rural areas forces people to resort to poor quality energy source, which is detrimental to the people's health and prevents the economic development of communities. Moreover, access to safe water and food security are concerns closely linked to health issues and children malnourishment. Recent climate change due to global warming has worsened the already critical situation.Electricity is well known to be an enabler of development as it allows the use of modern devices thus enabling the development of not only income-generating activities but also water pumping and food processing and conservation that can promote socioeconomic growth. However, all of this is difficult to achieve due to the lack of investors, local skills, awareness by the community, and often also government regulations.All the above mentioned barriers to the uptake of electricity in rural Kenya could be solved by the coordinated effort of government, private sector, and academia, also referred to as Triple Helix, in which each entity may partially take the other's role. This chapter discretizes the above and shows how a specific county (Marsabit) has benefited from this triple intervention. Existing government policies and actions and programs led by nongovernmental organizations (NGOs) and international agencies are reviewed, highlighting the current interconnection and gaps in promoting integrated actions toward climate change adaptation and energy access

    Plants and Plant Products in Local Markets Within Benin City and Environs

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    AbstractThe vulnerability of agriculture systems in Africa to climate change is directly and indirectly affecting the availability and diversity of plants and plant products available in local markets. In this chapter, markets in Benin City and environs were assessed to document the availability of plants and plant products. Markets were grouped into urban, suburban, and rural with each group having four markets. Majority of the plant and plant product vendors were women and 88 plant species belonging to 42 families were found. Their scientific and common names were documented as well as the parts of the plant and associated products available in the markets. Most of the plant and plant products found in local markets belong to major plant families. Urban markets had the highest diversity of plants and plant products. Three categories of plants and plant products were documented. Around 67% of the plants and plant products were categorized as whole plant/plant parts, 28% as processed plant parts, while 5% as reprocessed plant/plant parts. It was revealed that 86% of these plants are used as foods, 11% are for medicinal purposes, while 3% is used for other purposes. About 35% of plants and plant products across the markets were fruits, which is an indication that city and environs are a rich source of fruits. The local knowledge and practices associated with the plants and plant products can contribute towards formulating a strategic response for climate change impacts on agriculture, gender, poverty, food security, and plant diversity
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