Bioactive glasses have the ability to bond to bone in vivo, but they are brittle and cannot be used in load bearing applications. In this thesis, a process was developed to toughen bioactive glasses by forming a hybrid material for bone tissue engineering using the sol-gel process. As a first step, in preparation for polymer incorporation into the sol-gel process, the pH of the sol-gel synthesis had to be raised to milder pH conditions to prevent acid chain scission hydrolysis of the polymer. Solgel glasses were synthesised under the modified conditions and no adverse effects were found due to raising the pH of synthesis from pH < 1 to 5.5. These mild pH conditions were then used to synthesise hybrids of silica and calcium salt poly(γ-glutamic acid) (γCaPGA). γCaPGA was used as the toughening agent and as a low temperature calcium source with 3-glycidoxypropyl trimethoxysilane (GPTMS) providing covalent coupling between the inorganic and organic components. Hybrids of 40 wt% γCaPGA of all molecular weights tested (120 to 30 kDa) had large strain to failure (> 26 %) which showed that γCaPGA hybrids successfully softened the brittle behaviour of sol-gel glasses. However, the polymer dissolved preferentially due to its hydrophilic nature. All γCaPGA hybrids were found to form hydroxycarbonate apatite (HCA) within one week in SBF, even though they contained a low calcium concentration of 5 wt% when compared with 17.5 wt% Ca in Bioglass®. Formation of HCA is the first step in bonding to bone in vivo which is a fundamental requirement of materials for bone tissue engineering. Calcium was not only important for bioactivity, but also for ionic crosslinking, which improved compressive strength and reduced strain to failure when compared with identical hybrids made without ionic crosslinking. Although hybrids synthesised with γCaPGA dissolved too quickly for bone applications, calcium chelating polymers have been shown to offer great promise for bone tissue engineering.

The aims of the project were to produce and characterise phosphate-based glasses and glass-fibres, which were to be utilised as cell delivery vehicles. Initially the project aim was to attach muscle cells to the fibres in order to formulate alternative therapies for diseases such as Muscular Dystrophy. However, as the project progressed other cell types were also evaluated for the biocompatibility of the glass-fibres produced. Using a custom built fibre-rig (UCL) glass fibres were produced from compositions based on the ternary P205-CaO-Na20 glass system. These glasses were composed of ionic components that already exist in the body and thus minimal inflammatory responses were expected. This glass system had been investigated within the department, where the P205 content was fixed at 45 mol%, with the CaO and Na20 mol% making up the remainder. Initial studies revealed that fibres could not be produced from these compositions, and this was attributed to the structure of the glasses. By increasing the phosphate content to 50 and 55 mol% P205i glass fibres were successfully produced. Thus it was ascertained that a minimum of 50 mol% P205 was required for fibre production. Further analysis revealed that these ternary compositions proved to be too soluble for cell attachment. A quaternary component, boric oxide (B203), was added in order to reduce the degradation rates obtained. This was added due to the fact that B203 is a well known glass former. Further analysis revealed that B203 did reduce the degradation rates, however, these compositions also proved to be too soluble for cell attachment and proliferation to occur. A further quaternary component, iron oxide (Fe20s), was investigated. This was because iron is a naturally occurring ion within the body therefore, no inflammatory responses were expected. Fe2C > 3 was incorporated at 1 - 5 mol% substituted for Na20. It was seen that there was an order of magnitude difference with the degradation rates ranging from 1 - 5 mol% Fe203. Furthermore, it was seen that compositions containing 4-5 mol% Fe2C > 3 were sufficient for successful cell attachment and differentiation of muscle precursor cells. A further series of glasses were also investigated, incorporating silicon as the quaternary component. Silica was chosen due to the large volume of literature focusing on silica based glasses, with the well known Bioglass . Silicon was incorporated at 1- 5 mol%, and it was seen that silicon totally disrupted the glass network.

Polymeric biomaterials used for applications such as coronary and vascular bypass grafting have demonstrated poor patency due to their surface thrombogenicity, initiation of chronic inflammation and unfavourable host tissue responses. The aim of this thesis has been to develop a peptide which would demonstrate an inhibitory effect on blood coagulation and/or improved endothelial cell adhesion. Employing the RGD (Arginine-Glycine-Aspartate) peptide as a base, GRGD, GRGDS and GRGD(AhxGRGD)3 were produced. In order to allow incorporation of the peptide into the polymer matrix the corresponding lauric acid (LA) conjugated peptides were synthesised. In vitro determination of blood clotting time and tissue factor activity was utilised to determine the optimum peptide concentration for an anti-thrombogenic effect. Cytotoxicity and cell adhesion were assessed on endothelial cells. The results obtained suggest that LA-GRGD offered the best anti-thrombogenic effect whilst LA-GRGDS had the most improved cell adhesive effect. These two peptides were then used to investigate the surface modification of poly(carbonate-urea)urethane (PCU). The PCU surface was modified by passive peptide coating or peptide incorporation into the polymer matrix. Cell adhesion and activity studies showed that the incorporated LA-GRGDS peptide produced a significant (P < 0.05) improvement. Biocompatibility studies demonstrated no adverse effects with respect to either platelet adhesion or haemolysis. The inhibition of platelet factor 4 obtained with coated GRGD, GRGDS and incorporated LA-GRGD was comparable to that obtained with heparin coating. An in vitro flow study showed that significantly (P < 0.005) more incorporated peptide (42.6%) was retained on the surface of the polymer after 8 hours flow compared to coated (20%). In conclusion the direct incorporation of an LA conjugated peptide into the matrix of the polymer was successful with the peptide retaining its activity. This process of incorporation by solvent casting is attractive from a commercial viewpoint and shows the potential for future development and use in a clinical situation to produce a surface modified PCU polymer.

It is important to be prepared in advance for a radiological incident should one occur in the UK. Such incidents could occur as a result of a nuclear reactor incident, a fire from a facility containing radioactive material or a deliberate release of radioactive material from a Radiological Dispersal Device (RDD). RDDs can either be explosive (a ‘dirty bomb’) or a device that silently contaminates an area or group of people. Assessment of radiation doses to exposed people would in most circumstances include making measurements of the amount of the radionuclide in the body. Usually, body monitoring calibrations for such measurements are made using a physical model of the body (a “phantom”) containing a known amount of radioactive material. Such phantoms are almost always constructed for measurements on adult males. However, in an RDD incident, men, women and children of different ages and different body sizes could be exposed. Using a calibration phantom with different physical attributes to the person being measured gives rise to a larger statistical uncertainty in the measured activity. Furthermore, calibrations with physical phantoms may not have been performed for the radionuclides that might be encountered. Radionuclides that are inhaled may be distributed non-uniformly in the respiratory tract, which will affect the detector efficiency for lung calibrations. Commercially available phantoms typically use a uniform radionuclide distribution. Phantoms designed to be used in a supine position do not always provide reliable calibrations for measurements on people made in a seated geometry, which presents problems for emergency monitoring applications. Mathematical phantoms can be applied to overcome all of these limitations. A research project (VOXPOP) is under way to develop mathematical phantoms and mathematical detector systems for use with particle transport codes such as MCNPX. Research is currently being carried out to produce more realistic phantoms that represent the range of subject sizes and used for calibration of body monitoring measurements occurring hours or days after the incident. The research is applicable to both hand-held and portal monitors that can be used for screening measurements, and dedicated static and mobile body monitoring systems.

The elucidation of the brain’s anatomical and functional organisation during specific tasks is a challenging field in modern brain research. There is also a growing interest in the field of brain connectivity and its relation to specific motor and mental tasks, as well as neurodegenerative diseases like Parkinson’s and Alzheimer’s. In this thesis, a novel approach for modelling motor tasks is proposed. This approach combines diffusion adaptation and brain connectivity measures in order to build models which describe complex tasks through time and space. In particular, an S-transform based measure is introduced to estimate the connectivity on single-trial basis. The connectivity values, corresponding to different frequency bands across time, are effectively coupled with diffusion adaptation. The diffusion strategy exploits the time-space characteristics in a distributed and collaborated manner, and leads to an enhanced model for motor or mental tasks. Specifically, the imaginary part of S-transform coherency is introduced as an EEG connectivity measure. The performance improvement over the existing connectivity measures on a single-trial basis is demonstrated. Moreover, diffusion Kalman filtering is used as it performs well for nonstationary problems like this. This novel method is tested on various scenarios. Initially, its performance is demonstrated for simulated datasets which are based on realistic scenarios. Then, the method is applied to two datasets of real data. The first set of experiments includes a complex motor task of clockwise and anticlockwise hand movement and the second set includes a multi-modal dataset acquired from Parkinson’s patients. The results show that the connectivity enhanced modelling outperforms the simple case where connectivity information is ignored, and can build a robust task-related model.

This research was carried out to characterise mechanical properties of the large intestine. Assessing the mechanical properties of tissue plays an important role in understanding the links between histological structure and physical properties, physical functioning and normal anatomy. The mechanical properties of large intestine are poorly understood but essential for more accurate characterisation of their behaviour, for example during interaction with surgical instrumentation or devices. This project was set in the context of designing a new robotic colonoscopy device. The aim of this study was to develop and evaluate a robust methodology to characterise the ex-vivo mechanical properties of porcine large intestine tissue and create a database of these properties. In order to study the unique and complex physical properties of the large intestine two common techniques were employed: indentation and tensile stretching. A series of indentation and tensile tests were conducted and the time, strain-rate and strain history dependent responses of porcine large intestine during loading and stress relaxation were observed. Linear and non-linear models were used to analyse the tissue response. The results identified strong dependency of the large intestine mechanical properties to strain-rate and loading history. Tissue preconditioning was also found to be an effective way to stabilise the tissue response in air. Tissue hydration was also found to better preserve the natural state of tissue similar to the in-vivo environment. One of the most important observations was the necessity to produce an appropriate testing protocol for such investigations. Guidelines are proposed to set the requirements for mechanical tissue characterisation. For in-vivo investigation of tissue properties, a system based on measuring acoustic impedance properties of the tissue was successfully designed. Stiffness and tissue relaxation properties of the large intestine were examined using this probe and the results were linked back to the indentation outcomes. This system has the capability to be miniaturised and deployed during conventional colonoscopy or robotic hydro-colonoscopy.

Raman spectroscopy is an important emerging tool for biomedical research, with a growing number of medical applications. Raman probes allow chemical analysis to be carried out in-situ, and often in places no other analytical technique can reach. The design of a Raman probe is a large factor in its performance, the subsequent success of the application. In this work, a number of Raman probe designs are evaluated and the underlying factors for their performance investigated. It is found that the internal Raman scattering inside a probe is an important factor in its performance, an area previously seen as of marginal benefit. A probe is presented that uses this design paradigm to gain some useful performance characteristics: reduced interference from background, and improved medical compatibility. A new application for a Raman needle probe is also explored: monitoring of subcutaneously injected drugs. The needle probe is found to show promise for this technique, but performance improvements must be made before it can be applied without caveats. Finally, the safety of infra-red laser light was also evaluated directly by assessing the viability of cells after exposure. The results suggest that the current safety guidelines are excessively conservative and further investigation into this is recommended.

This thesis focuses on the development of novel nanomaterials for biomedical imaging using both iron oxide nanoparticles and cadmium based quantum dots, and two different coating methods. The first approach involved a coating ligand consisting of the stealth molecule polyethylene glycol, and a bisphosphonate enabling strong binding to the nanoparticle surface. This polymer conjugate was chosen in order to reduce undesirable reticuloendothelial system uptake, and hence increase blood circulation times allowing for efficient delivery of particles to specific in vivo vascular targets. The second route employed a naturally occurring amphiphilic protein, hydrophobin, as an encapsulation agent according water solubility of nanomaterials and potential for bioconjugation. The first part of the study involved the synthesis of novel iron oxide nanomaterials of small size distribution and a near-zero surface charge resulting in dispersions that were stable in solution for several months. Both longitudinal (r 1) and transverse (r 2) relaxivity measurements were performed at a clinically relevant magnetic field of 3 T, revealing a low r 2/r 1 ratio of 2.97 showing the particles to have optimal properties for efficient T1-weighted magnetic resonance imaging. The strong T1 effect was validated in vivo, revealing a long blood circulation time and a 6-fold enhancement of its signal, allowing for high resolution visualisation of vessels and vascularised organs. The low reticuloendothelial system uptake observed was confirmed by radiolabelling the particles, hence according dual-modality contrast, and performing in vivo single photon emission computed tomography. From this study, the blood half-life was calculated to be 2.97 h. In vitro targeting studies using three different cardiovascular/cancer biomarkers (VCAM-1, PSMA, and p32) were conducted, showing specific uptake of the targeted particles to relevant cell lines. The second section examines the potential for applying the polyethylene glycol-bisphosphonate coating to other inorganic nanomaterials. CdZnSeS alloyed quantum dots were successfully synthesised, with the resulting particles exhibiting red emission (_604.0 nm) and no significant shift after phase transfer into aqueous solution. Preliminary in vitro cell studies revealed particle emission at the expected wavelength. Finally, the synthesised nanoparticles were successfully coated with the amphiphilic protein (hydrophobin). The resulting nanoparticles exhibited no change in core size or morphology as determined by transmission electron microscopy, as well as no shift in emission (~627.0nm). In vitro studies were performed allowing for visualisation of the quantum dots in a biological environment after incubation at physiological temperature. In addition, particles were injected intratumourly into a live mouse model, with emission detected up to 24 h post injection. Lastly, radiolabelling with iodine-131 was achieved; confirming the possibility of utilising exposed residues on the protein to further functionalise the surface. In conclusion, the described methods and nanoparticles synthesised represent a promising platform for the development of targeted agents for multimodal medical imaging and other bio-applications.

Biomaterials play an essential role in modern medicine replacing and or facilitating normal physiological function. Despite their many advantages they serve as reservoirs for bacterial adhesion and subsequent biofilm infection. These are extremely difficult to treat, displaying resistance to conventional antibiotics up to 1000 times that of planktonic bacteria. In addition, biomaterial associated infections have a significant impact on patient recovery time and healthcare budgets. Researchers are developing biomaterial coatings in order to prevent bacterial adhesion and biofilm development. Taking inspiration from nature, antimicrobial peptides are now coming to the forefront of research and development. Variation of the R group attached to the alpha carbon confers peptides with tailored therapeutic, biodegradable and toxicity profiles. Synthetic peptides may be exploited for a variety of applications including as antimicrobial biomaterials and drug delivery vehicles. Ultrashort peptides (<7 amino acids) are a highly innovative and economical development strategy. These not only possess the tunable properties of longer peptides but they have the ability to self-assemble to hydrogel structures in response to external stimuli including pH, light, temperature and enzymes. Ultrashort self-assembling peptides are considered as novel ’smart’ nanomaterials. This thesis focuses on the development of a library of ultrashort self-assembling peptides prepared following standard Fmoc solid phase synthesis protocols and confirmed using NMR, RP-HPLC and ESI-MS. pH induced assembly resulted in hydrogel formation. Hydrogels were physically characterised using Cryo-SEM, TEM, oscillatory rheology, FTIR, CD and TGA. Antimicrobial activity was determined against a range of Gram-positive and Gram-negative biofilm forming healthcare associated pathogens and in vivo Galleria mellonella infection models. Toxicity profiles were determined via in vitro haemolysis and cell culture assays. The work highlights the promising contribution of ultrashort self-assembling peptides to future biomaterial development.

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