The evaluation of prosthetic ankles/feet and the study of the gait of trans-femoral amputees (TFAs) in different walking conditions are essential for improving prostheses design and supporting TFA rehabilitation and prostheses selection. To date limited work has been done in these areas and this study aimed to address some of the existing limitations by investigating the effect of hydraulic ankles/feet (Echelon and Elan) on the gait of conventional TFAs compared with a fixed ankle/foot (Esprit) during common daily activities. Five active male unilateral conventional TFAs and fourteen non-amputees participated in this research. Spatial-temporal, kinematic and kinetic gait data were determined for level ground self-selected normal and fast speed walking, 2.5° camber walking, and ascending and descending a 5° slope. Assessment of gait symmetry was given particular focus in the data analysis. Participant feedback was obtained from questionnaires. The results for the conventional TFAs showed significant improvement with the hydraulic ankles/feet in the sagittal plane ankle moment Trend Symmetry Index. This may support a claim of enhanced prosthetic knee stance stability when using these feet. In addition, greater range in prosthetic ankle dorsiflexion/plantarflexion, and increased first vertical ground reaction force peak at the prosthetic side were found compared with the fixed ankle/foot. The subject questionnaire results supported a preference for the hydraulic ankles/feet over the fixed ankle/foot. There was no significant difference found between the Echelon and Elan foot from the gait or questionnaire data. The strategies of conventional TFAs for adapting to different activities were compared with the non-amputees. When walking on an inclined surface, reduction in impulse at the prosthetic limb is an important requirement, as is improvement of balance control. Future studies with increased number of conventional TFAs and osseo-integrated TFAs are suggested to test the findings on the improvement indicated by the use of hydraulic ankles/feet.

No description available.

A novel technology for the generation of light emitting somatic transgenic animals has been developed using lentiviral vectors where luciferase expression is transcriptionally regulated by tandem, synthetic, transcription factor binding elements. This allows signalling pathways in diseased organs to be monitored continually and consciously and in a non-invasive manner. I was able to confirm my hypothesis that long term somatic transgenesis could be achieved within the CNS after a single neonatal intracranial injection of the biosensors. No signs of activated microglia or astrogliosis from the injection or the vector expression was observed. I generated several lentiviral biosensors and this included an astrocyte specific biosensor GFAP. I established and validated a Hypoxic Ischemic Encephalopathy mouse model in outbred CD1 mice. I applied somatic transgenic technology to the HIE mouse model to investigate whether it was possible to predict the severity of the disease in live mice. Unexpectedly, the luciferase expression from the four biosensors failed to correlate with the extent of brain infarct or the weight of the mice. To investigate this surprising results, I challenged the underlying assumption that GP64 enveloped lentiviral vectors target GFAP positive astrocytes. Interestingly very few astrocyte positive cells were being targeted by the GP64 pseudotyped lentiviral vectors. As GFP expression from lentiviral vectors was limited and mainly situated around the injection site, I investigated the use of AAV delivery to the CNS. AAV8 vector generated strong and homogenous GFP expression. An AAV8 NFκB biosensor was made and injected intracranially to new-born mice. This showed substantially more stable luciferase expression compared with lentivirus vectors.

Pluripotent stem cells (PSCs) are the most favourable sources of cells for tissue engineering applications due to their unique potency and self-renewal characteristics however they are quite fragile and can be directed to differentiate erroneously by the application of external forces. A novel multi-nozzle valve-based bioprinting platform was developed that was able to position droplets of bio-ink – such as cells in suspension – with high spatial accuracy and low impact. Volumes as low as 2 nL were successfully dispensed. Several different versions of the machine were created before the final machine was made integrating improvements and solutions to problems encountered during development. A complete evaluation of cell compatibility was carried out in order to quantify the response of cells to the bioprinting process. In the first ever study of this kind, the viability and pluripotency of human embryonic and induced pluripotent stem cells was investigated post-printing and were found to be almost completely unaffected by the bioprinting process. Many cells require a 3D culture environment in order to maintain their in vivo functions. A hybrid bioprinted-hanging-droplet technique was used to create uniform spheroid aggregates of programmable sizes from PSCs which could be used to direct PSC differentiation or as building blocks for tissue generation. Hydrogels can also be used to recreate the 3D in vivo cellular environment using the bioprinter. Alginate and hybrid polypeptide-DNA hydrogels were used, the latter for the first time with a bioprinting platform. Complex 3D structures could be created in a layer-by-layer approach with programmable heterogeneous properties throughout. Cells were added to the hydrogel precursor solution and used to bioprint 3D structures. The cells were found to be functional and highly viable while being encapsulated throughout the 3D structure of the bioprinted hydrogel which will allow the future creation of more accurate human tissue models. PSCs were successfully directed to differentiate into hepatocyte-like cells. It was shown that the bioprinting process did not interrupt or alter the pre-programmed differentiation of the cells which means that these cells can be patterned in 3D using the bioprinter while differentiating, greatly speeding up the creation of mini-liver tissue. Hepatic stellates and HUVECs were co-cultured with the hepatocyte-like cells in various ratios in an attempt to improve their hepatic function. However, no clear improvement in cytochrome P450 activity was observed indicating that further optimisation is required in this area.

Research claims in the biomedical domain are not always consistent, and may even be contradictory. This thesis explores contradictions between research claims in order to determine whether or not it is possible to develop a solution to automate the detection of such phenomena. Such a solution will help decision-makers, including researchers, to alleviate the effects of contradictory claims on their decisions. This study develops two methodologies to construct corpora of contradictions. The first methodology utilises systematic reviews to construct a manually-annotated corpus of contradictions. The second methodology uses a different approach to construct a corpus of contradictions which does not rely on human annotation. This methodology is proposed to overcome the limitations of the manual annotation approach. Moreover, this thesis proposes a pipeline to detect contradictions in abstracts. The pipeline takes a question and a list of research abstracts which may contain answers to it. The output of the pipeline is a list of sentences extracted from abstracts which answer the question, where each sentence is annotated with an assertion value with respect to the question. Claims which feature opposing assertion values are considered as potentially contradictory claims. The research demonstrates that automating the detection of contradictory claims in research abstracts is a feasible problem.

No description available.

Atrial fibrillation (AF) is the most common cardiac arrhythmia in clinical practice, and it increases the chance of stroke fivefold. The mechanisms underlying the initiation and preparation of AF are still not clearly understood. Dominant frequency (DF) analysis has been widely used as a feature for the analysis of atrial electrograms. Atrial regions that contain high DF (HDF) signals are believed to correspond to the underlying AF drivers. HDF sites have been proven largely unstable in time and space. However, cyclic behaviours of HDF reappearance were noticed in the LA during persAF, suggesting that AF is not totally random. Similarly, re-entrant activity, also known as ‘rotors’ or spiral waves, have been shown to exist in atrial arrhythmias, and are believed to drive AF. Recently, drifting and unstable rotor behaviours were observed in persAF. The current work aims to develop techniques and tools to better track important features, especially when they are spatiotemporal unstable, such as HDF and phase singularities (PSs), to study the underlying AF mechanisms. In this work, a novel interactive graphic user interface was implemented, compatible with a commercial electro-anatomical mapping system (EnSite, St Jude Medical), providing additional features that are not currently available in commercial systems, to guide catheter ablation of persAF. In addition, a new algorithm has been developed to identify reappearing HDF patterns, and these recurring patterns showed high organisation, which could be important atrial sites for ablation. This is the first algorithm that could track recurrent patterns in DF analysis. Lastly, the performance of state-of-art PS detection methods was firstly investigated in non-contact mapping, suggesting that PS detection are method-dependent. Optimised parameters of the methods were proposed to increase detection accuracy for PSs detection in AF.

The use of bioceramic materials for the repair and regeneration of injured or diseased parts of the musculoskeletal system is a longstanding area of interest. However, the possibility to extend their range of applications, particularly for load-bearing bone defects and shape them into custom-built geometries is still an open challenge. Beyond the state of the art, this research work focused on the processing and characterisation of eight novel silicate, phosphate and borate glass formulations (coded as NCLx, where x=1 to 8), containing different oxides and in diverse molar percentages. The glass frits were provided by GTS Ltd (Sheffield, UK) along with apatite-wollastonite (AW), used as comparison material. In the first part of the work glass powders were characterised in terms of physico-chemical and biological properties. Subsequently, the glass powders were processed in form of dense bulk materials, and their sintering and mechanical behaviour was evaluated. On the basis of the biocompatibility data, assessed using rat osteoblasts, three formulations were selected for further characterisation. In vitro bioactivity testing using simulated body fluid showed that after 7 days of incubation the three materials, and NCL7 in particular, showed the formation of globular shape apatite precursor precipitates, indicating the bioactive behaviour of these glasses. In the last part of the study, 3D porous structures were manufactured via a binder jetting, powder-based 3D printing technology. The sintered 3D printed parts exhibited architecture and mechanical property values similar to those of AW. In addition, the in vitro biocompatibility indicated a biological positive response with a cell viability comparable to AW after 7 days. The research overall has processed and characterised a range of novel bioceramic formulations, and demonstrated the potential and effectiveness of the 3DP strategy to manufacture highly reproducible ceramic-based structures.

Prior work has shown that spin-coating tunicin cellulose nanowhiskers onto a glass surface creates a highly oriented surface that supports the adhesion, spreading and proliferation of myotubes. Building on this work, this project aimed to develop culture surfaces with biologically active topography and tuneable stiffness with the aim of better mimicking native muscle tissue. The ultimate aim is to develop biomaterials that can direct the differentiation of mesenchymal stem cells. Cellulose nanocrystals (CNWs) from Ascidiella spp were isolated and characterised. Polyelectrolyte multilayers (PEMs) are nanocomposite films formed from the sequential deposition of oppositely charged polymers and offer a flexible method of building films with a variety of chemical compositions and physical properties. CNWs were used in combination with chitosan to create PEMs using a combination of two well-established, low-cost and facile production methods, dip-coating and spin-coating. The resulting PEM was shown to be a nanoporous substrate that was stable under cell culture conditions. It robustly allowed the attachment, alignment and myogenic differentiation of the immortalised C2C12 myoblast cell line. Proteomic analysis of the ECM produced by C2C12 cells in response to the substrate showed that cells cultured on CNW-chitosan PEMs secreted increased fibronectin, tenascin-c, elastins and collagen I, an expression pattern that is consistent with a more developmental, rather than mature, muscle ECM. The thickness and mechanical stiffness of the PEM films could be tuned by replacing replacing increasing volume fractions of CNWs with poly(4-sodium styrene sulfonate) (PSS). The thickness of the dry films increased with increasing CNW content, increasing from 20 nm for films containing 12 bilayers of PSS and chitosan to 100 nm for films containing 12 bilayers of CNW and chitosan. The compressive stiffness of hydrated films decreased with increasing CNW content, from 1.67 ± 0.73 MPa, to 1.06 ± 0.24 MPa. Unfortunately, PSS-modified PEMs proved to be cytotoxic to cells. The response of bone marrow stem cells to the substrates showed that mesenchymal stem cells were contact guided by the CNWs, but did so by avoiding the material, thus being better guided by substrates where CNWs were present at a low surface density than substrates where it was present at a high density. When cultured directly on PEMs, MSCs expressed myogenin, a key marker of terminal muscle differentiation, which was suggestive, but not definitive, of a potential of the biomaterial to direct the myogenic differentiation of MSCs.

The work contained within concerns itself with the synthesis and characterisation of phosphonated polymers intended for application as nanofibrous tissue scaffolds for improving the healing of bone; it is based on previous work performed in the University of Manchester that identified poly(ε-caprolactone) (PCL) nanofibres coated with poly(vinylphosphonic acid-co-acrylic acid) (PVPA-co-AA) as a promising material for enhancing bone healing. This thesis initially focuses on the characterisation of a commercially sourced PVPA-co-AA by defining its composition and molar mass using quantitative 31P NMR and aqueous gel permeation chromatography. A method of synthesising the copolymer by free radical polymerization, with controlled rates of monomer addition, was developed to produce PVPA-co-AA copolymers with a range of compositions. Additionally, nanofibres of PVPA-co-AA were then formed by electrospinning and crosslinked with ethylene glycol; the subsequent nanofibres were found to be water stable and retain their structure after hydration and subsequent drying. A block copolymer, polycaprolactone-b-poly(acrylic acid) (PCL-b-PAA), was synthesised by four-step ATRP and two-step NMP based approaches, with the block character of the resulting copolymer being demonstrated by GPC and dynamic light scattering. The PCL-b-PAA was subsequently used as a compatibiliser for PCL and PVPA-co-AA emulsions, which were used to create composite nanofibres by electrospinning. These nanofibre were in turn characterized by scanning electron microscopy and compared to nanofibres formed using a surfactant, Span® 80, and the original dip-coated nanofibres. Finally, a small portion of work was undertaken to develop phosphonated PCL analogues, by attempting to synthesise phosphonated ε-caprolactone monomers.