Because of recent advances in medical technology, patients who have undergone severe trauma or illness are surviving where they would not have in the past. In many instances it is necessary for patients' stay in hospital to be protracted for a number of months until they are sufficiently medically fit for discharge. Many times, before such a patient can return as a productive member of society a programme of intensive rehabilitation is necessary. Amongst the most difficult tasks confronting those responsible for rehabilitating such long stay non-acute patients, is that of rehabilitating a quadriplegic. Quadriplegia, or as it is sometimes referred to, - tetraplegia - is defined as the partial or total loss of motor function in both upper and lower limbs. This thesis deals with some of the problems that are presented by patients who suffer quadriplegia, and with practical engineering solutions to some of these problems. Functional rehabilitation, by augmenting and supplementing the patient's residual ability so that he may most effectively interface with his surroundings, is the chief theme of this work. Particular emphasis is laid on the contribution of the bio-engineer to the efforts of the team of specialists assigned to rehabilitate the quadriplegic. The purpose of this project is two-fold, being directed tov1ard returning as great a degree of independence to the patient as possible, and relieving to some extent the burden placed on the family and those having to tend to the patient's needs.

This thesis was almost wholly conducted in the confines of the Department of Bio-engineering and Medical Physics, University of Cape Town and the Bio-engineering Unit, Princess Alice Orthopaedic Hospital, Cape Town. It is an interdisciplinary thesis in that an effort has been made to bridge and thus unify the different scientific disciplines of Physics, Biology, Electrical Engineering and Mathematics. Thus the author hopes the work would appeal to as wide an audience as possible. The thesis is directed generally towards a deeper understanding of normal and pathological biped locomotion. It involves theoretical considerations in respect of model building, model testing and practical work concerned with the collection of pertinent data.

Skeletal muscle fibers develop from mono-nucleated myoblasts that fuse to form multinucleated myotubes. In embryonic growth, this process occurs concurrently with the formation of the early cartilaginous skeleton and innervation by migrating nerve cells. The goal of my research was to explore co-culture conditions that encourage proliferation, differentiation and maturation of myoblasts to myotubes. A variety of co-culture experiments tested the influence of three basic tissues types (murine neural, cartilage and kidney primary cells) on the formation of myotubes in the C2C12 myoblast cell line. Three plating strategies were used: 1) C2C12 myoblasts were plated first, grown for two days before the addition of a second cell type; 2) both cell types were mixed and plated simultaneously; and 3) C2C12 myoblasts were added to a pre-established, 10 day old neural, cartilage or kidney cell culture. In addition, a parallel set of experiments were treated with all-trans retinoic acid, a potent myogenic activator and embryonic patterning signaling molecule. Myotube formation was consistently highest in C2C12 and cartilage co-cultures across all three plating strategies with a 277% increase in myotube area compared to controls. These effects were further enhanced when grown in 1 µg/mL all-trans retinoic acid. Co-cultures with neural or kidney cells consistently exhibited fewer myotubes when compared to C2C12 controls. It is postulated that the enhanced muscle growth in cartilage co-cultures was due to a chondrocyte-secreted extracellular matrix that facilitated myotube attachment to the substratum. / Graduate

Spider silk is a material that both has impressive mechanical properties and is also environmentally friendly. Though there are limitless potential engineering applications for such materials, industrial production of spider silk has proven to be challenging. Farming silk from spiders, as is done with silkworms, is not a viable option for large-scale production of spider silk due to the venomous and predatory nature of spiders. Here, an attempt is made to express synthetic spider silk minifibroins heterologously in Escherichia coli, to purify the recombinant spidroins from cell lysate, and to spin them into artificial fibers through a biomimetic process. Silk minifibroins were designed to be similar to Major Ampullate Spidroin 1 from Latrodectus hesperus. Synthetic fibers were examined by scanning electron and light microscopy, and their mechanical properties were tested by a tensometer. Properties of synthetic silk were compared to those of native dragline silk from the same species from which their design was inspired, revealing synthetic silk fibers with lower breaking stress and breaking strain.

No description available.

Qu’est-ce que la bio-ingénierie ? Assimilée à l’essor des nouvelles manières de manipuler et contrôler le vivant par la modification du génome depuis les années 70-80, la bio-ingénierie est fréquemment identifiée et restreinte aux biotechnologies à ADN. Ingénieriser le vivant est alors synonyme du développement des plantes génétiquement modifiées et des transformations de l’industrie pharmaceutique qui témoignent de l’apparition d’un nouvel agencement entre science, industrie et politique. Au milieu des années 2000, une communauté d’ingénieurs se rassemble autour du terme de « biologie synthétique » avec pour ambition de faire advenir la « vraie » bio-ingénierie. Davantage qu’un nouveau domaine scientifique, cette communauté naissante revendique une véritable utopie technique de modification du vivant sur le modèle de l’électronique et de l’informatique en rupture avec les biotechnologies à ADN et leurs régulations. Cette utopie est néanmoins marginalisée et la biologie synthétique se range alors comme un domaine scientifique stabilisée.La thèse enquête à partir de l’émergence de la biologie synthétique pour interroger les pratiques et les régulations de la bio-ingénierie depuis le milieu des années 80. Suivre la bio-ingénierie permet alors de mettre à jour un régime de production de savoir à l’ombre des biotechnologies à ADN et des récits dominants sur la manière dont le savoir contemporain est produit. L’expression « à l’ombre » renvoie alors aux régulations délaissées, aux applications peu révolutionnaires, aux acteurs puissants et discrets, aux secteurs économiques peu enquêtés, aux programmes peu étudiés pour rendre compte de ce que l’on appelle les biotechnologies et de la production de savoirs contemporaine. / What is bioengineering? Associated to the rise of the ways of manipulating and controlling the living through the modification of the genome since the 70s-80s, bioengineering is frequently identified and restricted to DNA biotechnologies. Engineering the living is then synonymous with the development of genetically modified plants and transformations of the pharmaceutical industry which testify to the appearance of a new arrangement between science, industry and politics. In the mid-2000s, a community of engineers gathered around the term "synthetic biology" with the ambition to bring about the "true" bio-engineering. More than a new scientific field, this emerging community claims a real technical utopia of modification of life based on the model of electronics and computer technology breaking with DNA biotechnologies and their regulations. This utopia is nevertheless marginalized and synthetic biology ranks as a stabilized scientific domain.The thesis starts from the emergence of synthetic biology to interrogate the practices and regulations of bioengineering since the middle of the 80's. Following bioengineering then allows to update a regime of production of knowledge in the shadow of DNA biotechnologies and dominant narratives of how contemporary knowledge is produced. The term "in the shadow" then refers to neglected regulations, non-revolutionary applications, powerful and discrete actors, the economic sector under investigation, under-researched programs to account for is commonly called biotechnology and contemporary knowledge production.

Vegetation can increase the resistance of slopes against landsliding. The mechanical contribution of roots to the shear strength of the soil is however difficult to measure in situ. Existing methodologies are time-consuming and therefore not suitable to quantify spatial variability on the slope. Furthermore, some existing methods, for example large in situ shear box testing, can be difficult to apply on remote sites with difficult access, e.g. steep slopes. Therefore in this thesis novel, simple and portable methods to quantify mechanical root-reinforcement in the field were developed. The ‘blade penetrometer method’, one of these new methods, was based on standard penetrometer testing but used an adapted tip shape to increase sensitivity to roots. Root depths and diameters could be quantified based on characteristics of the depth–resistance trace, both in the laboratory and in the field. Several new analytical interpretive models were developed to predict the force–displacement behaviour of roots loaded under various conditions: one assuming roots broke in tension and another assuming roots broke in pure bending. Both methods did take root–soil interaction into account. Based on these models, some roots were shown to have broken in bending and others in tension, depending on plant species and root diameter. Two new methods were developed to measure the root-reinforced soil strength directly. The ‘pin vane’ was an adaptation of a standard field shear vane, replacing the cruciform blades of the latter by prongs to minimise the effects of soil disturbance and root breakage during installation. This was one of the main problems encountered when using standard vanes in rooted soil. This ‘pin vane’ method was qualitatively shown to be able to measure the reinforcing effects of both fine and thick roots (or root analogues), both in the laboratory and the field. This method will be most useful when the strength of densely rooted surface layers is to be analysed, e.g. for erosion resistance purposes. Another newly developed shear device was the ‘corkscrew’. Rotational installation of the screw ensured minimal soil and root disturbance. During vertical extraction the root-reinforced shear strength was mobilised along the interface of the soil plug caught within the screw. The measured extraction force could be related to the reinforced soil strength. This method underestimated the strength in surface layers (especially at 0–125 mm and less so at 125–250 mm depth) but functioned well in deeper soil layers important for landsliding. Although laboratory results were promising, during in situ testing in deeper layers ( > 125 mm) local variation in soil stress, gravel content and water content, combined with low root volumes, made it difficult to accurately quantify the effect of the roots. Where the effect of roots was pronounced, e.g. in more heavily rooted surface layers (0–125 mm), significant positive trends between the measured soil strength and root strength and quantity were found. Measured reinforcements were small compared with various root-reinforcement model predictions but comparable to direct shear tests on rooted soil reported by others. These new methods, although still in the early stages of development, showed promising results for practical use in field conditions. The equipment was simple to use and portable, enabling measurements on sites with difficult accessibility. However, more work is required to validate the interpretive models developed and to calibrate these methods for a wider range of soil and root conditions.

Le tissu adipeux est traditionnellement décrit comme étant constitué de lobules : des entités de formes ovoïdales composées de cellules et de vaisseaux et faiblement connectées entre elles.Récemment, il a été montré qu’un potentiel métabolique spécifique (le browning) co-localise avec cette organisation en lobules au sein d’un même tissu. Dans ce travail de thèse, nous nous intéressons à décrire plus précisément l’organisation structurelle et fonctionnelle du tissu adipeux selon plusieurs aspects. Dans un premier temps, on s’attache à segmenter les lobules du tissu adipeux en utilisant une méthode de traitement d’image originale. Nous mettons en évidence une organisation 3D complexe et suivant plusieurs échelles. En particulier, il semble que le potentiel de browning soit également lié à une organisation structurelle particulière en clusters de lobules. Dans un second temps, à partir d’imagerie 3D, nous reconstruisons le réseau vasculaire entier du tissu adipeux et réalisons une simulation d’écoulements sanguins micro-vasculaires. Plusieurs hétérogénéités structurelles et fonctionnelles sont alors mises en valeurs à l’aide d’une analyse en communautés qui composent le tissu adipeux (par algorithme de clustering). Ces résultats confirment l’existence d’une zone centrale fortement vascularisée et qui se démarque également comme étant le lieu d’une perfusion sanguine d’intensité différente. Dans une dernière partie, nous abordons la question de transferts thermiques entre vaisseaux sanguins suivant des géométries simples mais pertinentes. Nous réalisons une étude systématique des paramètres adimensionnels clés du problème et mettons en évidence un invariant des échanges de chaleur : un optimum à faible nombre de Péclet (convection de même ordre que la diffusion). Nous introduisons également une méthode de calibration de paramètres effectifs dans le contexte des modèles homogénéisés de température à travers des tissus vascularisés. / Adipose tissue is traditionally described as consisting of lobules: ovoid-shaped entities composed of cells and vessels and weakly connected to each other. Recently, it has been shown that a specific metabolic potential (browning) colocalize with this organization in lobules within the same tissue. In this thesis work, we are interested in describing more precisely the structural and functional organization of adipose tissue from several aspects. We first perform a segmentation of adipose tissue lobules using an original image processing method. We highlight a complex 3D organization and relevant on several scales. In particular, it seems that browning potential is also linked to a particular structural organisation in clusters of lobules. In a second step, using 3D imaging, we reconstruct the entire vascular network of adipose tissue and simulate micro-vascular blood flow. Several structural and functional heterogeneities are then highlighted using an analysis in communities among adipose tissue (by clustering algorithm). These results confirm the existence of a highly vascularized central area that also stands out as the site of a more marked blood perfusion. In a last part, we approach the question of heat transfers between blood vessels following simple but relevant geometries. We carry out a systematic study of the key dimensionless parameters of the problem and highlight an invariant of heat exchanges: an optimum at low Péclet number (convection of the same order as diffusion). We also introduce a method of calibrating effective parameters in the context of homogenized temperature models across vascularized tissues.

No description available.

Stem cell bioengineering and therapy require different model systems and materials in different stages of development. If a chemically defined biomatrix system can fulfill most tasks, it can minimize the discrepancy among various setups. By screening biomaterials synthesized through a coacervation-mediated self-assembling mechanism, a biomatrix system optimal for 2D human mesenchymal stromal cell (hMSC) culture and osteogenesis is identified. Its utility for hMSC bioengineering is further demonstrated in coating porous bioactive glass scaffolds and nanoparticle synthesis for esiRNA delivery to knock down the SOX-9 gene with high delivery efficiency. The self-assembled injectable system is further utilized for 3D cell culture, segregated co-culture of hMSC with human umbilical vein endothelial cells (HUVEC) as an angiogenesis model, and 3D bioprinting. Most interestingly, the coating of bioactive glass with the self-assembled biomatrix not only supports the proliferation and osteogenesis of hMSC in the 3D scaffold but also induces the amorphous bioactive glass (BG) scaffold surface to form new apatite crystals resembling bone-shaped plate structures. Thus, the self-assembled biomatrix system can be utilized in various dimensions, scales, and geometries for many different bioengineering applications.