The main hypothesis of this research project was that optimisation of treatment based on pharmacokinetic principles is on its own a powerful approach in improvement of treatment outcomes. This work therefore focused on optimisation of treatment of cancer based on principles of pharmacokinetics using two main approaches 1) lipophilic prodrug approach to specifically target the intestinal lymphatic system following oral administration and 2) identification of orally bioavailable candidate anticancer agents and biopharmaceutical development to increase the bioavailability for sufficient systemic exposure to the drug. The first approach was the prodrug derivatisation to take advantage of the physiological process of intestinal lymphatic transport in order to deliver anticancer agents to the mesenteric lymph nodes. Similar prodrug approaches have been researched by other groups but the main focus previously was on increasing the overall bioavailability where they mostly used long-chain or triglyceride mimetic prodrug moieties. However, in this project, through a series of stability and chylomicron association studies, it was revealed that activated ester prodrugs are the most suitable forms for yielding high concentrations of active drugs in the mesenteric lymph nodes. It was remarkable that using this novel approach significantly higher concentrations of the active drugs were achievable in the intestinal lymphatics without affecting the systemic exposure. The second approach taken in this PhD project was achieving sufficient systemic exposure of anticancer agents by identification of orally bioavailable candidate and improvement of oral bioavailability by biopharmaceutical development. The candidates with promising pharmacokinetic properties were rank-ordered by application of a rational drug discovery and development approach of integrated in vitro-in silico assessments. Following in vivo confirmation studies, oral bioavailability was further enhanced for a compound that exhibited a double-peak phenomenon. The results of the two approaches indicate that pharmacokinetic optimisation can be useful in development of anticancer agents to improve the treatment outcomes of cancer.

In order to achieve drug delivery via the respiratory route, an understanding of particulate interactions is of vital importance. For successful delivery to the distal airways, an aerodynamic diameter of less than 5 μm must be achieved. However, particles of this size presents a difficult formulation challenge, due to the inherent cohesiveness between particles and adhesion to the device, due to the high surface to volume ratio of such small particles, causing the particles to clump together. This tendency will thereby cause a reduction in dispersion, aerosolisation and device efficiency; for this reason dry powder inhalers (DPIs) invariably fail to achieve a fine particle fraction efficiency above 15%. There are a wide variety of factors which affect particulate interactions including; surface roughness, surface chemistry, particle size or shape and particle mechanical properties. However, these factors are highly interrelated and so previous attempts to investigate their effect on particle adhesion generally have difficulty isolating the impact of each factor. For instance, investigating the effect of morphology on particulate interactions invariably utilise destructive techniques to alter the roughness, which is likely to alter other factors like surface energy and provide limited control for optimisation. With the rise of 3D printing (additive manufacturing) there is now the capability to produce sub- micron morphologies, and so a bottom-up approach to studying the effect of morphology on particulate interactions can be achieved. The aims of this thesis are therefore twofold. Firstly, to identify, optimise and evaluate a suitable additive manufacturing technique to produce well-defined micron scale morphologies appropriate for furthering the understanding of the importance of morphology on particle adhesion. This is a scale which is at least two orders of magnitude improvement on current state of the art 3D inkjet printers. Secondly, to measure the effect on particle adhesion and deposition to these morphologies, both on an individual particle and on a bulk powder basis, allowing elucidation and understanding of the effect of surface roughness on particle adhesion, with a specific focus on respiratory drug delivery. Printing well defined geometries of an appropriate micron scale size range for particle adhesion testing has been achieved, using two photon polymerisation (TPP). TPP is a novel 3D printing technique which as its name suggests involves the curing of usually acrylate containing polymer resins by the absorption of two infra-red photons in the focus of the laser beam. TPP has been shown to produce a sub-diffraction limit lateral resolution of 120 nm. By optimising the printer parameters and experimentation with differing structure fill and input settings the creation of a well- defined curve on a micron scale was achieved. The initial test morphologies comprised of a ridge with a semi-circular top with a diameter of 1 μm, which were shown to be reproducibly printed. These morphologies were then varied in a controllable fashion with varying ridge height and spacing between the ridges. A uniform and consistent surface chemistry was created using a plasma polymerised hexane (ppHex) coating. In order to evaluate particulate interactions relevant to pulmonary drug delivery both an understanding of the effect of morphology on both individual particle adhesion and bulk powder deposition in a fluid environment is needed. Individual particle-surface adhesion was achieved by testing the TPP structures against three particle types using single particle colloidal probe microscopy (polystyrene beads diameter 10 μm and 5 μm and a lactose particle designed for inhalation formulations). The analysis of this data provides evidence of a clear trend between particle contact area and adhesion recorded both on the ppHex control and the TPP coated morphologies. The TPP morphologies are shown to locally reduce the overall adhesion, in comparison to the flat substrate. The ridge height is also seen to have a significant effect on particle adhesion, with 5 μm < 3 μm < 1 μm for the polystyrene beads, but 3 μm < 5 μm < 1 μm for the Respitose SV003 lactose particle for all ridge spacings. Varying the ridge spacing produced two differing trends in adhesion to the polystyrene beads. If the particle was unable to penetrate the valleys of the roughness, for the 1 μm high ridges, a significant effect on particle adhesion was seen with 3 μm < 1 μm for the polystyrene beads. In contrast, the 3 μm and 5 μm high ridges showed the opposite trend when the particle is unable to descend between the ridges with 1 μm < 3 μm < 8 μm for the polystyrene beads. Investigation of the bulk powder deposition of the particles on the TPP structures and any subsequent re-entrainment in a fluid environment was then achieved using a novel methodology developed during the course of this work. This combines the use of a standard next generation impactor, which generally is used to separate out a respiratory formulation based on aerodynamic diameter, with the TPP substrates. This shows that ridge height has a significant effect on particle adhesion with 3 μm < 1 μm < 5 μm. In contrast, the different spacings of the ridges were not shown to produce a significant difference in particle deposition. This is likely due to the conflicting effect of asperity spacing on the processes of particle deposition and re-entrainment. This thesis therefore highlights the capability of TPP, to produce well-defined micron scale structures with varying morphologies. It then shows that these can be successfully utilised to provide valuable insight into the effect of surface morphology on particle- surface interactions, specifically; adhesion, deposition and re-entrainment.

The pharmaceutical industry has experienced an increase in the amount of development candidates with low aqueous solubility and accordingly poor bioavailability. In order for this problem to be solved, amorphisation is thought to be the most favourable solution. The amorphous state is higher in free energy thus higher in solubility when compared to the crystalline form. Milling and specially cryomilling is a very unique technique for providing of the crystalline to amorphous transformation since there are no heat or solvents involved. Phthalic acid, isophthalic acid and terephthalic acid, individual and pair mixtures, are crystalline organic non medicinal compounds, which have been used for the first time as model compounds to investigate whether cryogenic milling can induce crystal to amorphous transformation and if the preparation of pair mixtures could affect the recrystallization rate of the subjected materials or not. The materials were cryomilled and analysed by DSC, XRPD, and FTIR. It was found that only terephthalic acid become amorphous after cryomilling, and even after the cryomilled sample been stored for three weeks DSC thermogram still detects recrystallization exothermic along with the XRPD pattern, which shows a very broad peaks indicative of particle size reduction. Pair mixtures were also studied and analysed by DSC and XRPD. Phthalic acid/isophthalic acid, isophthalic acid/terephthalic acid, phthalic acid/terephthalic acid were cryomilled together and mixed physically after been cryomilled separately. XRPD results show that unlike the cryomilled separately mixtures, phthalic acid/ isophthalic acid, isophthalic acid/terephthalic acid, terephthalic acid/phthalic acid cryomilled together samples produces a synergistic effect in which the Bragg peaks of both phthalic acid and isophthalic acid are suppressed. It appears that co cryomilling of these pair mixtures together resulted in the production of a new material that could potentially either be two-component single phase (nano-sized co-crystal), or a new polymorphic form of either phthalic acid, isophthalic acid or terephthalic acid. Single-component of aspirin (ASP), paracetamol (PCM) and caffeine (CAFF), along with multi-component systems of paracetamol/aspirin, paracetamol/caffeine and aspirin/caffeine were milled at room temperature and by a cryomill. The milled samples were analysed using DSC, XRPD and FTIR. It was noted that there are no clear indications of crystal to amorphous transformation in all three materials. When milling aspirin at room temperature a marked reduction in the melting point was observed. Generally, a reduction in the melting point is either attributed to particle size effects, polymorphism, impurities and decomposition. In this case, the decrease in the melting point was only noticed when aspirin was milled at room temperature, so it is possible that the heat generated during the milling process resulted in chemical decomposition of aspirin to salicylic acid. Anhydrous caffeine is acknowledged to have two polymorphic forms, Form II which is considered to be stable at room temperature until ~145 °C. Form I is stable from ~145 °C to its melting point ~ 236 °C. This polymorphic transformation was detected by DSC, XRPD and hot stage microscope and it was noticed only with the as received and the room temperature milled samples. Cryomilled caffeine data showed only the presence of Form I. On the other hand, for the cryomilled multi-component systems DSC and hot stage microscope images confirmed the eutectic formation with a composition of 45:55% w/w (PCM:ASP), 50:50% (ASP:CAFF) AND 50:50% (PCM:CAFF). The obtained data were compared with room temperature milled and the theoretical values resulted from Van Laar equation. Solid pharmaceuticals represent heterogeneous systems that typically consist of one or more active pharmaceutical ingredients (APIs) and a number of excipients. Multi-component systems from mixing aspirin, paracetamol and caffeine with different excipients, which included sucrose, lactose monohydrate, xylitol and trehalose dihydrate were prepared by the use of a cryomill and were analyesd by DSC and XRPD. It was found from the XRPD data that mixing both sucrose and lactose monohydrate respectively with ASP, PCM and CAFF would produce more of a synergistic effect than xylitol and trehalose dihydrate. Cryomilling caffeine/sucrose and caffeine/lactose resulted in a production of a new XRPD trace that cannot be described in terms of a linear combination of caffeine, sucrose and lactose monohydrate. A new material was therefore formed as a result of cryomilling which has not been reported before.

Made available in DSpace on 2015-10-06T13:03:06Z (GMT). No. of bitstreams: 0 Previous issue date: 2020-10-05. Added 1 bitstream(s) on 2015-10-06T13:18:59Z : No. of bitstreams: 1 000849923.pdf: 2014627 bytes, checksum: 1b6eae4b9c988513760eff69d5c21a37 (MD5) / Membranas poliméricas de PVDF, PVDF/TiO 2 e PVDF/TiP foram obtidas com êxito pela técnica de fiação por sopro em solução. Inicialmente foi realizado um estudo sobre a influência da concentração de PVDF em solução de DMF, na obtenção de membranas de PVDF puras. As micrografias obtidas destas membranas mostraram que a variação da concentração do PVDF influencia a morfologia e o diâmetro das nanofibras. Os resultados obtidos por difratometria de raios X mostraram a presença da fase β polar do PVDF. A influência da incorporação de TiO 2 em solução de PVDF/DMF também foi estudada. As micrografias obtidas das nanofibras de PVDF/TiO 2 mostraram que as incorporações não afetam a morfologia. As nanofibras, se apresentaram aleatoriamente dispersas, homogêneas e sem uma orientação preferencial. As análises por difratometria de raios X realizadas nas nanofibras identificaram a fase β do PVDF e a fase anatase do TiO 2 . As micrografias das nanofibras puras de PVDF/TiP apresentaram morfologias homogêneas, rugosas e sem o aparecimento de contas. Também foram obtidas nanofibras puras de TiO 2 . Essas nanofibras foram obtidas após o processo de queima das mantas de PVDF/TiP. As nanofibras puras de TiO 2 apresentaram uma morfologia que varia de acordo com o tratamento térmico recebido. Para as nanofibras tratadas termicamente a 400, 600 e 800 °C, as morfologias apresentadas são formadas pela união dos grãos de TiO 2 . As nanofibras tratadas a 1000 °C apresentaram uma morfologia lisa e a formação de nanofibras ocas. A difratometria de raios X das nanofibras de TiO 2 identificou picos característicos da fase cristalográfica anatase nas amostras tratadas a 400 e 600 °C. Para o tratamento a 800 °C é observado além da fase anatase a fase rutilo em menor proporção. No entanto, nas nanofibras tratadas a 1000 °C é observado apenas a fase rutilo. As mantas de PVDF obtidas neste trabalho podem ser utilizadas na área... / PVDF, PVDF/TiO 2 and PVDF/TiP membrane of were successfully prepared by solution blow spinning method. A study on the influence of concentration of PVDF in DMF, to obtain PVDF nanofibers without incorporation of nanoparticles was performed. The micrographs show that the variation of PVDF concentration influences the morphology and the diameter of the nanofibers. The results obtained by diffraction X-ray showed the presence of the β-phase of PVDF. The influence of TiO 2 incorporated in the PVDF/DMF solution was studied. The micrographs PVDF/TiO 2 nanofibers showed that the incorporation do not affect the morphology, they present randomly dispersed, homogeneous and without a preferred orientation. X-ray diffraction identified the β phase of PVDF and the anatase phase of TiO 2 . The micrographs PVDF/TiP nanofibers showed homogeneous morphology, and without the appearance of beads. Also obtained were pure TiO 2 nanofibers. The TiO 2 nanofibers were obtained after the burning of PVDF/TiP nanofibers. The nanofibers produced presented a morphology dependent of heat treatment. Nanofibers heat treated at 400, 600 and 800 °C are formed by the union of TiO 2 grains. However, the nanofibers obtained at 1000 °C are smooth and hollow. The X-ray diffraction of TiO 2 nanofibers identified the anatase phase in the samples obtained at 400 and 600 °C. The sample obtained at 800 °C was observed anatase and rutile in lower proportion. In nanofibers obtained at 1000 °C was observed only rutile phase. PVDF blankets those obtained in this work can be used as filters and the TiO 2 incorporation can add the photocatalytic property. The pure TiO 2 nanofibers can also be used in photocatalysis and in hybrid cells using the TiO 2 as electron acceptor

Resultados obtidos de processos (p,2p) coplanares são apresentados através de diagramas de contorno das distribuições de momentum, no espaço de momentum. Os diagramas de contorno, traçados para o exemplo da reação 16O(p,2p) 15N, para os estados nucleares ls e lp, a energias de bombardeio de 200 MeV e de 378 MeV, mostram-se muito sensíveis à distorção causada pelos potenciais óticos que atuam sobre os prótons incidente e emergentes. Os diagramas apresentam-se deformados e deslocados em relação às formas circulares centradas na origem que teriam, no espaço de momentum, na ausência de distorção. A deformação e o deslocamento de cada diagrama são consequência, respectivamente, da absorção e do espalhamento elástico dos prótons de alta energia. / Results obtained from (p,2p) coplanar processes are presented by means of contour diagrams of momentum distributions in momentum space. The contour diagrams obtained for the example of the 16O(p,2p) 15N reaction, for the nuclear states ls and lp, at borábarding energies of 200 MeV and 378 MeV, appear to be very sensitive to the distortion caused by the optical potentials which act on the incident and emergent protons. Compared to the diagrams obtained in the absence of distortion, which are circular and centered at the origin, in momentum space, the distorted diagrams appear deformed and shifted. The deformation and the shift of each diagram are a consequence of the absorption and the elastic scattering of the high-energy protons, respectively.

A proteção física é um importante mecanismo de estabilização da matéria orgânica (MO) em solos subtropicais. Desenvolveu-se quatro estudos sobre essa temática em solos com textura e mineralogia distintas, sendo os estudos 1 e 2 relacionados à avaliação de produtos (iodeto-NaI e politungstato de sódio-PTS) e de densidades de solução (1,8 a 2,2 g cm-3) sobre o rendimento das frações leve livre (FLL), leve oclusa (FLO) e pesada (FP) da MO do solo. Por sua vez, os estudos 3 e 4 objetivaram avaliar o efeito de sistemas de manejo de solo na agregação e acúmulo de C orgânico no solo, bem como verificar a importância da oclusão no acúmulo de C nas camadas de 0-5, 5-10 e 10-20 cm de um Argissolo Vermelho (220 g kg-1 argila) e de um Latossolo Vermelho (680 g kg-1 argila), há 18 e 25 anos, respectivamente, sob plantio direto (PD). Do ponto de vista metodológico verificou-se que na densidade de 1,8 g cm-3, o uso da solução de PTS resultou num aumento de 176 a 726% no C quantificado como FLO em comparação ao NaI, enquanto não foi verificado efeito significativo no rendimento do C na FLL. O aumento da densidade da solução de PTS de 1,8 para 2,0 g cm-3 aumentou de 30 a 99% o rendimento de C na FLO, não tendo sido verificado vantagens na recuperação de C com o uso da solução de 2,2 g cm-3. O sistema PD resultou num aumento dos estoques de carbono (C) orgânico e na estabilidade de agregados em comparação ao solo em preparo convencional (PC), sendo este efeito mais expressivo na camada superficial do solo (0-5 cm). Os estoques crescentes de C nas frações (FLL>FLO>FP) em ambos os solos indicam o efeito aditivo dos mecanismos de recalcitrância molecular, oclusão e proteção coloidal na estabilidade da MO do solo. O sistema PD não resultou em aumento no C da FLL em comparação ao solo em PC, indicando que as alterações no microclima, normalmente verificadas sob este sistema de manejo conservacionista, não foram responsáveis pelo acúmulo de C orgânico nos solos avaliados. Por outro lado, o PD promoveu aumento no C da FLO, evidenciando-se que a oclusão foi responsável por aproximadamente 30% do acúmulo de C orgânico nos solos sob este sistema conservacionista de manejo, em comparação ao solo em PC. A solução de PTS 2,0 g cm-3 é a mais adequada para os solos estudados em avaliações da proteção física da MO do solo, mecanismo o qual contribui expressivamente para o acúmulo de C orgânico em camadas superficiais de solos em plantio direto no Sul do Brasil. / The physical protection is a important mechanism of soil organic matter (SOM) stabilization in tropical and subtropical soils. Four studies focusing this subject were developed using soils with different texture and mineralogy. Two studies evaluated products (sodium iodide-NaI and sodium politungstate -SPT) and density of solutions (1.8 to 2.2 g cm-3) on C recovery in the free light fraction (FLF), occluded light fraction (OLF), and heavy fraction (HF) of the SOM. Other two studies evaluated the effect of the no-tillage (NT) on soil aggregates stability and on organic C accumulation, as well as the importance of the mechanism of occlusion on the C accumulation in the soil profile (0-5, 5-10 and 10-20 cm) of a sandy clay loam Paleudult (220 g kg-1 clay) and of a Rhodic Hapludox (680 g kg-1 clay). The use of 1.8 g cm-3 of solutions of SPT had a C recovery in the OLF 176 to 726% higher than using NaI solution, while no significant effect was verified on the C recovery in the FLF. The increase of density of SPT solution from 1,8 to 2,0 g cm-3 recovered from 30 to 99% more C in the OLF, while no advantages were verified on C recovery using density of 2.2 g cm-3. NT soil had higher aggregate stability and the stocks of organic C in comparison to conventional tillage (CT) soil, effects that were more pronounced on the surface soil layer (0-5 cm). The increase of C stocks in the fractions (FLF>OLF>HF) in both soils indicated an additive effect of the mechanisms of molecular recalcitrance, occlusion, and colloidal protection in the stability of the SOM. C stock in the FLF not increased in NT soils in comparison with CT soils, indicating that the microclimate alterations usually verified under this conservation management system were not responsible for the C accumulation in the evaluated soils. On the other hand, NT increases the C in the OLF, evidencing the occlusion as a mechanism responsible for approximately 30% of the C accumulation in the NT soils, in comparison with CT soils. The solution of SPT 2,0 g cm-3 was the more appropriate for using in studies of physical protection of the SOM in the evaluated soils, mechanism that have an important role to the C accumulation in the surface soil layers of Southern Brazilian no-tilled soils.

The prediction of percutaneous absorption is of enormous importance for the effective design, development and quality assessment of topical and transdermal formulations. In vitro diffusion experiments are widely carried out for such predictions and are of substantial interest across the pharmaceutical and cosmetic industries. Human or animal skin, usually excised, are often used in in vitro drug diffusion studies. However, difficulties in obtaining the mammalian skin and variation in their permeability directed researchers towards using synthetic membranes as skin mimics in preformulation screening experiments, where a large number of experiments are required. Polydimethylsiloxane (PDMS) membranes have been accepted as the most commonly used in vitro skin mimic because of their homogeneity, uniformity and skin-analogous rate-limiting permeation properties. This thesis investigates the effects of ionisation and surfactants on the permeation of pharmaceutical compounds of varied physicochemical properties through PDMS membranes using a flow-through diffusion cell system. Data suggests that drug permeation had a dependency on the extent of its ionisation, with the permeation being more favourable for the more unionised form of a drug. All of the surfactants studied were found to reduce the permeation of the drugs, with an inverse relationship being observed between the surfactant concentration and the amount of drug permeated. DSC (differential scanning calorimetry), SEM (scanning electron microscopy), FTIR (Fourier transform infrared) and NMR (nuclear magnetic resonance) spectroscopy were employed to study the interactions between the membrane and the surfactants. Results indicated that the permeation effects of the surfactants are a consequence of the interactions between the drugs and surfactant micelles, and/or the membrane and the surfactants. Air plasma treatment was used to modify the PDMS surfaces to become hydrophilic, which was confirmed by water contact angle (WCA) and SEM-EDX analysis. The permeation data for the modified membranes revealed that the plasma-induced hydrophilicity significantly reduced the fluxes of the hydrophobic compounds, while not affecting that of the hydrophilic drug. Aging studies of the plasma-treated membranes showed that the hydrophilic surfaces were maintained even after 8 weeks under airtight storage conditions. In summary, ionisation and surfactant effects on drug permeation across PDMS were thoroughly investigated, and plasma treatment was found to be a stable, economic and convenient method of modifying PDMS to offer skin-like slower drug permeation i.e. to produce a potential in vitro skin mimic.

An investigation into the aspects of innovation within the downstream domain of the pharmaceutical supply chain This research evaluates the implementation of innovative programmes within the downstream domain of the Pharmaceutical Supply Chain (PSC). Pharmacies are considered as key links between healthcare services and patients because they are responsible for dispensing and managing pharmaceuticals in order to prolong life. Considering the healthcare organisations‘ crucial role and that they face the challenge of minimising the cost of healthcare services while enhancing service quality, healthcare organisations tend to try improvement approaches and innovative interventions to enhance their efficiency and effectiveness. Specifically, they tend to focus on improving their Supply Chain Management (SCM) in order to reduce waste, in particular with regards to their medicine expenditure, and to provide improved services. However, implementing innovation within the Pharmaceutical Supply Chain (PSC) is not yet adequate; at present there appears to be a lack of experience and knowledge of how such initiatives should be undertaken. Research that examines potential innovative contributions might therefore make a defined contribution to the sector. This research, therefore, aims to assess the current medicine delivery process and identify the issues responsible for weak process performances and the factors that influence pharmacies‘ innovativeness within two diverse European contexts, the UK and Greece. An exploratory research design, embracing a mixed-methods approach, was used to analyse the issues associated with PSC inefficiency and assess to what extent innovation could be adopted by hospital and community pharmacies to improve the delivery process of pharmaceutical products. The qualitative data was gathered through 30 interviews with key professionals working within the downstream domain of the PSC in the two selected geographical areas. A total of 21 in-depth interviews in the UK and 9 in Greece were conducted to examine the elements preventing the effective and efficient delivery of medicines. Simultaneously, an online survey was developed to collect the quantitative data. The final sample (N=130) consisted of specialists working within the down stream domain of the PSC in Greece and the UK. The quantitative data analysis aimed to identify the factors that support or prevent innovation within this specific and complex environment. The analysis and combination of these two sets of data enabled the researcher to gain a comprehensive understanding and recommend innovative solutions that are suitable to the system under investigation, leading to continuous improvement. This research contriputes to academic literature as it adds more theoritical insights to innovative delively processes, especially those that have been characterised as highly complex. The results led to the generation of the Innovative Pharmaceutical Supply Chain Framework (IPSCF) that provides guidelines to healthcare organisations about how the identified problems can be overcome by implementing suitable innovative techniques. The implementation of Lean and Reverse Logistics practices, which are supported by integrated Information Technology (IT) systems, are suggested as a means for healthcare organisations to enhance their delivery system in terms of quality (products and service quality), visibility (knowledge and information sharing), speed (respond to customers and suppliers needs) and cost (minimisation of cost and waste) and therefore generate a competitive edge. The study‘s recommendations have important implications for pharmacies, as they provide guidance regards suitable innovative programmes that can be adopted. The outputs of this research are specifically relevant to the pharmacy sectors of the UK and Greece, but may have also relevance for European healthcare organisations.

Chemical risk assessment for human health effects is performed in order to establish safe exposure levels of chemicals to which individuals are exposed. The process of risk assessment traditionally involves the generation of toxicological studies from which health based guidance values are derived for a specific chemical. For low level exposures to chemicals, where there are no or limited chemical specific toxicity data, the application of the Threshold of Toxicological Concern (TTC) approach may estimate whether the exposure levels can be considered safe. The TTC approach has recently gained increasing interest as new requirements, under different regulatory frameworks, emerge for the safety assessment of chemicals and to assess chemicals for which testing is not routinely required. The application of TTC relies heavily on computational (in silico) methods. In silico tools are computer implemented models that, based on commonalities in the toxicity of “similar” chemical structures, may predict hazard. In silico methods are rapidly evolving and gaining importance within the context of Integrated Approaches to Testing and Assessment (IATA) and their acceptance for regulatory purposes is expanding. The work presented in this thesis has focused on the use and applicability of a wide range of computational approaches to assist in the application of the TTC concept. In the TTC approach, the identification of genotoxic chemicals is a primary requirement. In silico approaches apply expert knowledge and/or statistical methods to either predict genotoxicity or to identify structural alerts associated with it. This thesis focused, in part, on a group of important environmental pollutants, nitrobenzenes, to assess the applicability of in silico tools to predict genotoxicity. For this purpose a dataset containing 252 nitrobenzenes including Ames test results was compiled. Based on these test results a case study for sodium nitro-guaiacolate, a pesticide active substance, was developed. The case study demonstrated that (Q)SAR and a category approach incorporating read-across, are applicable for the prediction of genotoxicity and supports their use within a weight of evidence approach. Another aspect of the TTC approach is the evaluation of repeat dose, non-cancer endpoints. For that purpose chemicals are separated into groups related to three levels of concern based on the Cramer classification. For each level, namely the Cramer Classes (I, II and III), a safe exposure level has been established. Therefore, as interest to apply TTC expands to new groups of chemicals, the reliability and conservativeness of the established thresholds relative to Cramer Classes for the new chemistries must be established. In this thesis the TTC approach was evaluated for 385 cosmetic ingredients, 77 biocides and 102 compounds classified as reproductive and developmental toxicants. To support the evaluation at different levels, chemical datasets containing toxicological data were utilised and computational tools were applied to compare datasets. The results indicated, that the historical “Munro” dataset is broadly representative for cosmetics and biocides. In addition, that the threshold levels for Cramer Class III are within the range of Munro’s threshold further supports the validity of the TTC approach and its conservativeness for the groups of chemicals analysed. Cramer Class I thresholds were found to be valid only for classified developmental and reproductive toxicants. The results also supported the validity of the classification of chemicals into Cramer class III. It is foreseen that the TTC approach will gain increasing acceptance in the risk assessment of different groups of chemicals. Therefore it is emphasised that the future work should focus on the identification of the limitations of the application of TTC, including the identification of groups of chemicals to which TTC cannot be applied, the expansion of the underlying toxicological datasets, and the development of tools to support the application of TTC so that is transparent and acceptable for regulatory purposes.

Clays and clay minerals (phyllosilicates) have been used for millennia to treat a range of human maladies, such as infected wounds and diseases of the skin. The unique chemistry of phyllosilicates allows them to support the wound environment and encourage healing. Their physicochemical properties can also be utilised to develop modified drug-release formulations and also enables their incorporation into polymer matrices for the development of advanced wound care materials. By developing novel antibacterial phyllosilicate-polymer composite materials it should be possible to support wound healing, whilst simultaneously treating infections locally to avoid systemic adverse effects and prevent the development of antimicrobial resistance. In this research project the clay minerals kaolin (KN), refined montmorillonite (rMMT), montmorilonite K10 (MMTK10), Laponite® RD (LRD), and Laponite® XL21 (LXL21) were investigated for their differing structure and physicochemical properties. Their ability to adsorb and desorb the antibacterial agents tetracycline (TC), doxycycline (DC) and ciprofloxacin (CIP) was determined through a series of adsorption kinetics and isotherm studies. LRD and LXL21 were shown to have the highest drug-carrying capacity and were also able to relinquish this drug-load to inhibit the proliferation of key wound pathogens; Staphylococcus epidermidis, Propionibacterium acnes, and Pseudomonas aeruginosa. XRD and FTIR analyses demonstrated that these drug molecules could be adsorbed into the interlayer space and edge groups of the Laponite® particles. LXL21-CIP composites were successfully incorporated into alginate polymer matrices through interaction of the exposed edge-groups on LXL21 and the hydroxyl groups of the alginate to produce novel nanocomposite film and foam materials. Selection of candidate materials was initially undertaken qualitatively with the support of a tissue viability nurse at the Royal Liverpool and Broadgreen University Hospitals NHS Trust. Important properties for wound-dressings such as adsorptive capacity, water vapour transmission rate, and keratinocyte compatibility were measured quantitatively and compared to materials already used for wound care in the UK. Both the film and foam materials were shown to have properties that would be beneficial for wound healing and were also able to release CIP in a controlled manner with notable activity against S. epidermidis, P. acnes, and P. aeruginosa. The nanocomposite film formulation developed in this research project showed promise for future clinical applications and future work should be undertaken to further optimise their manufacture and fully characterise their ability to support the healing of infected wounds. Although the nanocomposite foams require further research, the work presented in this thesis suggests they could also be promising materials for wound care applications.