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Physically disabled people belong to a stigmatised group that is subject to negative societal stereotypes of incompetence and dependency on others. In order to maintain a positive sense of self, as well as receive needed support from others, physically disabled people need to continually navigate the stigma associated with disability. In so doing, they may face a number of dilemmas about how to express their disabled identity to others. The core argument of this thesis is that managing these identity dilemmas can have implications for support-seeking behaviour, as well as individual health and well-being. To develop this argument, this thesis aimed: first, to investigate the way in which physically disabled people experience their identity; second, to explore the role of stigma in shaping the experience and expression of identity among disabled individuals; and third, to elaborate a model of identity performance to describe how physically disabled people enact their identities in ways that navigate the twin concerns of stigma and accessing needed support. Before presenting a series of studies designed to address these aims, Chapters 1 through 3 explore the existing literature and develop the rationale for the present work. Chapter 1 presents a substantive review of previous research into stigma and physical disability. This review includes studies of general attitudes about disability and toward disabled individuals from the perspective of the non-disabled, and studies documenting the experience of stigmatisation from the perspective of disabled individuals themselves. Chapter 2 presents the social identity approach as a general framework for understanding identity in the context of stigma, and for theorising links between these processes and individual outcomes in terms of health and well-being. This chapter extends the basic social identity approach by incorporating recent thinking about identity performance, and considers the applicability of this to the disability context. Chapters 4 through 6 present the empirical work undertaken as part of this thesis. Chapter 4 provides a qualitative investigation of the ways in which people with cerebral palsy experience stigmatisation when accessing support. These experiences demonstrate individual awareness of stigma in support-seeking contexts and that this awareness is associated with felt pressures to perform one’s disabled identity in specific ways. In particular, respondents reported a tension between needing to be seen as sufficiently disabled in order to qualify for others’ support, but also the need to downplay feelings of difference from non-disabled people when accessing this support. Chapter 5 explores this tension further via a series of three connected quantitative studies. Using self-report data, these studies assessed how the salience of stigma as an issue (Study 2), and the salience of specific stigmatising audiences (healthcare providers, the general public, educators and employers; Studies 3 and 4) might promote changes in how physically disabled people enact their selves, and the implications of this for subjective feelings of health and well-being, and willingness to engage in support-seeking behaviour. The key finding from these studies is that the salience of specific audiences (but not the issues to which these connect) can activate expectations of stigma in the form of negative meta-stereotypes, and that these activated stereotypes shape the form and consequences of individual identity expressions. Healthcare providers were associated with especially negative stereotypes about disabled people, and these stereotypes undermined individual health and well-being as well as willingness to engage with support. Consistent with our identity-based analysis of these processes, individual differences in identification were found to play a role in modifying responses to these salient audiences and the meta-stereotypes these audiences activated in Studies 3 and 4. Finally, Chapter 6 presents a further qualitative investigation designed to build on the insights of the previous four studies. Specifically, Study 5 delves deeper into physically disabled people’s experiences of stigma when interacting with healthcare providers, educators and employers, the behavioural pressures they felt when doing so, and the strategies they engaged to deal with those pressures. When interacting with healthcare providers, participants discussed concerns about their deservingness for care potentially being questioned, and so sought to perform their identity in ways that demonstrated their legitimacy or need for support. When interacting with educators and employers, participants were instead concerned about being devalued in terms of their competence, and so sought to demonstrate their identity in ways that amplified their capabilities. However, in enacting these performances, participants noted the possible negative implications these behaviours had for how they personally viewed themselves (and wanted to be viewed by others). In this sense, Study 5 demonstrated that disabled people face dilemmas in negotiating demands from their audience, while also attempting to maintain a positive view of their self. In the concluding Chapter 7, a final discussion is completed in which the results from the five studies are reviewed and integrated, and the theoretical and practical contributions this work are noted.

Vitamin D3 deficiency is a worldwide public health problem that can lead to a wide range of disorders including rickets, osteoporosis, and infections. Vitamin D3 has also been used as a therapeutical molecule systemically and locally, however, the numerous available oral and topical preparations suffer from low bioavailability. The aim of this project was to synthesise a new series of vitamin D3 analogues to improve the bioavailability of this essential chemical using the skin as the delivery route. A new series of vitamin D3 analogues were synthesised successfully, introducing a phosphate group to reduce their lipophilicity. The synthetic procedures were confirmed by NMR and LC/MS analysis. Ex vivo skin permeation studies using porcine skin in Franz diffusion cells determined the transdermal delivery of the new analogues with HPLC quantification. Cholecalciferol phosphate, a novel vitamin D analogue improved skin absorption significantly (p < 0.05) in both the acidic and salt forms, compared to cholecalciferol. Cholecalciferol phosphate disodium salt in a simple propylene glycol solution formulation exhibited the best skin permeation, showing 1,090.10 ± 500.38 μg/cm2 (43,604 IU) vitamin D transdermal penetration, which was 35-fold higher than cholecalciferol after 24 h A patch formulation containing cholecalciferol phosphate disodium salt also showed good penetration into the skin, with 299.60 ± 22.85 μg/cm2 vitamin D in the skin (11,983 IU) after 24 h, which was a 25-fold increase compared to the commercial patch. However, the phosphorylation of calcitriol did not improve its skin absorption. Experiments in rat keratinocytes demonstrated that the introduction of a phosphate group into cholecalciferol did not affect its biological activity with no mTOR inhibitory action. The phosphorylation of vitamin D3, enabled >100 times more than the minimum recommended daily supplement dose (400 IU) to pass through porcine skin thus being a viable route of delivery to enhance vitamin D bioavailability.

Human African trypanosomiasis (HAT) is fatal unless treated. Pentamidine has been used to treat first-stage (hemolymphatic) HAT since the 1940s, but it is ineffective against second-stage (meningoencephalitic, or central nervous system) infection. Research has suggested that hOCT1 and P-gp are involved in the transport of pentamidine across the blood-brain barrier (BBB). The aim of this study was to investigate if through the formation of ion-pairs the passive diffusion and hOCT1 and P-gp mediated BBB transport of pentamidine could be improved.

Topically applied vitamin E (α-tocopherol, α-T) can provide protection from ultraviolet radiation induced skin damage and photoaging. However, α-T is oxidized and due to its hydrophobicity it is not easily delivered into viable skin layers where it elicits its photo-protective effect. Alpha-tocopherol phosphate (α-TP), a chemically stable, water-soluble derivative of α-T, could have similar effects as α-T as well as it may be able to more easily reach epidermis. The aim of this thesis was to investigate the skin penetration of α-TP and its photoprotection in vitro. At concentration of 35 mM, α-TP was found to form aggregates with 9 nm hydrodynamic size at a critical aggregation concentration of 4.2 mM when dissolved in 20% ethanol, 20% propylene glycol, 60% tris buffer at pH 7.4. The AFM images showed that at low concertation's (~1 mM), α-TP formed spherical liposomes (diameter of 50 nm, height of 17 nm) and at high concentrations (6 mM) α-TP formed rods (diameter of 300-570 nm, height of 12 nm). The α-TP nanomaterial at pH 7.4 showed a 5-fold higher total skin deposition than α-T. In stratum corneum (SC) lipid monolayer model, the mean molecular area (MMA) per molecule of pure SC lipids at surface pressure of 30 mN/m (30.18 A2/molecule) increased with the addition of 30% α-TP (38.12 A2/molecule), this may be due increase the repulsive forces upon increasing the percentage of α-TP and thus weaken the attractive forces between SC lipids head groups and disrupt their packing. The 24 h pre- incubation of HaCaT keratinocytes with α-TP in low serum media significantly suppressed the cell viability reduction induced by UVA1 (226 J/cm2) by 14% compared to irradiated vehicle control and whereas α-T did not. In vitro α-TP displayed weak antioxidant activity using the DPPH and ORAC assay, but the radical-scavenging activity in HaCaT keratinocytes using pre-irradiation treatment with 100 μM α-TP significantly reduced the ROS generation by ~ 24% compared to the irradiated vehicle control. Adding SLN to the α-TP topical formulation to mimic sunscreen products enhanced the release of α-TP from a 2% lotion and 2% gel by 2-fold and 11-fold, respectively possibly by deaggregation. The α-TP could be delivered into the viable epidermis where it showed photoprotective effects and it seemed feasible to include the α-TP in topical sunscreen (e.g. SLN) formulation to add or maximize the protection.

Gram-negative bacteria possess numerous defence mechanisms against antibiotics, due to the intrinsic permeability barrier afforded by their outer membrane and the various efflux mechanisms which pump out drugs, explaining the recalcitrance of some common and lifethreatening infections. A novel compound, PPA148, was synthesised in-house and showed promising activity against Gram-negative bacteria. Nevertheless, in some clinical bacterial strains, drug efflux resulted in reduced efficacy was observed, which was reversed in the presence of the efflux pump inhibitor phenylalanine-arginine β naphthylamide (PAβN). A formulation of PPA148 consisting of a drug/cyclodextrin (drug/CD) complex encapsulated in liposomes is investigated as a way to increase drug uptake. PPA148 has very low water solubility, which was measured using spectroscopic techniques: photon correlation spectroscopy (PCS) and Ultra-Violet spectroscopy (UV). Its solubility is improved by complexation with βCD derivatives (HPβCD and RAMEB) and the complex is characterized by applying nuclear magnetic resonance (NMR) and fluorescence. Fluidosomes, loaded with the drug/CD complex, are manufactured by applying the thin-film hydration method followed by extrusion for reducing the size of liposomes. PCS is used to size the particles and measure their zeta-potential. A Stewart assay and UV were used to quantify the lipid and drug concentration respectively, in the final formulation. A disk diffusion microbiological assay is used to assess the efficacy of the formulation against E. coli (DH5a). A variety of in vitro biophysical techniques are used to assess the mechanism of the drug uptake. Phospholipids, Re Lipid A extracted from S. Minnesota and Rc J5 LPS extracted from E. coli are used to make a synthetic monolayer and bilayer model of the outer and inner bacterial membranes. They are adapted for use with the Langmuir trough (LT) and neutron reflectivity (NR) techniques to monitor changes occurring upon interaction with the drug alone and the formulated drug. The results revealed an possible increase in drug efficacy with a possible fusion mechanism of uptake. NR provides a new method to examine the fusion mechanism of fluidosomes with bacterial membrane.

Drug delivery via the skin is attractive, but it is challenging and thus it is an area of continual research. Challenges arise in this field because only a narrow range of drugs naturally diffuse into the cutaneous tissue. This natural passive skin diffusion process is largely dictated by the drugs physicochemical characteristics. Only moderately lipophilic, low molecular weight agents accumulate in sufficient concentrations in the systemic circulation after topical delivery to elicit a clinical effect. The inability of drugs to pass into the skin has been addressed in previous work through chemical and physical methods of penetration enhancement, but using the currently available technologies it remains problematic to force compounds through the skin without damaging the tissue. The aim of this project was to investigate if the application of topical hypobaric pressure, a new physical technique to enhance topical drug delivery, could be used to facilitate drug delivery into the skin without skin damage. To study the effect of local hypobaric pressure changes upon drug penetration into the skin three model systems were selected based on their different physicochemical properties; minoxidil (a small drug that passes into the skin via the hair follicles), dextran (a model macromolecule), and nanosized carriers (to simulate a drug delivery system). Application of the device (built-in-house) gave a stable pressure reading for 60 min. Histology, showed hypobaric pressure up to 400 ± 50 mBar did not damage the skin. The application of hypobaric pressure (400 ± 50 mbar) was shown to be significantly (P < 0.05) enhance drug deposition in the skin for the majority of test systems. For example, an enhancement ratio of 16.5, 5.3 and 5.2 was observed for minoxidil in 'stratum corneum', epidermis and dermis respectively. For solid lipid nanoparticles an enhancement ratio of 1.2, 8.8 and 7.8 was recorded for 'stratum corneum', epidermis and dermis respectively. For the dextran (FD-4) the enhancement ratios were 2.9, 2.0 and 1.2 for 'stratum corneum', epidermis and dermis respectively. The hypobaric enhanced skin permeation was dependent on the test systems size, surface charge, and hydrophobicity. Confocal microscope images showed the solid lipid nanoparticle enhancement was through the intercellular and follicular pathways, whereas the dextran enhancement was through the intercellular pathway when hypobaric pressure was applied. In conclusion the results obtained from this project suggested that the application of hypobaric pressure was an effective, safe and promising method to enhance the delivery of drugs into the skin and it warrants further assessment in vivo to enable its clinical use.

Specific ligand targeting has been shown to facilitate drug transport across biological membranes. The aim of this PhD was to investigate whether ion-pairing a drug (theophylline) with a polyamine transporter system (PTS) substrate (polyamine) could actively target drug delivery into the lungs from the pulmonary circulation. To try and achieve this, cyclodextrins were used in a co-solvent to engineer a physically stable cyclodextrin-ion-pair complex. FT-IR and HPLC binding assays showed that theophylline (THE) bound most tightly to spermine (SP) (THE-SP: pKFT-IR = 1.96 ± 0.04, pKHPLC = 2.81 ± 0.06) than to spermidine (SPD) (THE-SPD: pKFT-IR = 1.93 ± 0.05, pKHPLC = 2.79 ± 0.065) followed by ethylenediamine (EDA) (THE-EDA: pKFT-IR = 1.43 ± 0.02, pKHPLC = 2.49 ± 0.05) and the least with ethylamine (EA) (THE-EA: pKFT-IR = 1.32 ± 0.04, pKHPLC = 2.43 ± 0.042). Ion-pairing theophylline with the counter-ions significantly increased the drug’s solubility and reduced its lipophilicity. The formation of 1:1 cyclodextrin/[theophylline-spermine] ion-pair complexes were confirmed by NMR. Reducing the dielectric constant of the vehicle was found to increase the binding affinity of theophylline to spermine (pKTHE-SP in 70 % PG: pKTHE-SP = 2.11 + 0.045 > pKTHE-SP in 10% EtOH: 2.05 + 0.053 > pKTHE-SP in water: 1.96 + 0.06) when assayed with FT-IR. However, it was found that the ion-pair, regardless of the vehicle used or when complexed with cyclodextrins, dissociated rapidly when the pH of the solution was dropped to 7.4. The theophylline-spermine uptake in A549 showed that the PTS was involved in the membrane transport of the drug. In addition, a sustained delivery of theophylline was achieved when cyclodextrin was complexed with the ion-pair, which suggested cyclodextrins could stabilize the ion-pair association. Hence, a cyclodextrin-theophylline-spermine complex described herein represents a potential for lung targeting delivery.

This thesis investigates whether the formation of ion-pairs can influence the delivery of salbutamol to the airways of the lung. Presenting a drug with an excess of oppositely charged ion can force it to form an ion-pair complex, and this complex can modify a drug’s dissolution or transport across epithelia without chemically altering the drug. The binding of salbutamol with pharmaceutically relevant counter ions was studied. It was found that the larger more hydrophobic counter ions bound more tightly to the drug. Only 2 of the investigated counter ions had a significant effect on the LogD7.4 of salbutamol. Phytic acid was investigated as a novel counter ion. Generation of phytic acid derivatives was attempted via chemical synthesis however this method did not yield a pure sample. The binding of phytic acid was studied and was found to be stronger than the other investigated counter ions, although no change in the logD7.4 of salbutamol was observed. Salbutamol ion-pair dry powders with particle size < 5 μm were generated via spray drying. Impactor testing found that the powders were in the respirable range. Stability testing after 4 weeks found that the powders containing both PVP and l-leucine were the most stable after this time. The biocompatibility of the counter ions with Calu-3 human bronchial epithelial cells was assessed and all counter ions were shown to be well tolerated. The effect of the ion-pairs on the transport of salbutamol across a monolayer of Calu-3 cells found a significant difference in the transport of the sulfate, gluconate and phytate ion-pairs when compared with salbutamol base. There was no significant difference in the dissolution of the phytate or octanoate powders when compared with the base. An in vivo bronchoprotection study of salbutamol base and phytate was performed. The work in this thesis suggests that an ion-pairing strategy is suitable for use to prolong drug action in the lung.

Oral microbial disease is highly prevalent globally and is being associated with a multitude of systemic illnesses. There is a vast range of oral health products containing tooth hardening and antimicrobial agents yet the problem persists. The aim of this thesis was to chemically modify the anti-inflammatory vitamin E in order to introduce novel substantive antimicrobial activity giving it multifunctional activity to combat oral disease. (+) Alpha tocopherol (α-T) was chemically modified by phosphorylation to generate (+) alpha tocopheryl phosphate (α-TP). (+) α-TP was observed to form nano sized aggregates with a μM critical aggregation constant when dispersed in Tris buffer. The addition of the phosphate group was found to introduce substantive antimicrobial activity as (+) α-TP retarded Streptococci biofilm growth, adhered to hydroxyapatite and inhibited salivary biofilm growth whilst (+) α-T did not. This activity was related to nanostructure architectures as (+) α-T formed spherical, non-surface adherent liposomes (563 ± 1 nm, -10.5 ± 0.2 mV) whilst (+) α-TP formed surface adherent, planar bilayer islands (175 ± 21 nm, -14.9 ± 3.5 mV). Tris facilitated (+) α-TP antimicrobial activity as when it was dispersed in phosphate buffer it did not penetrate, kill or retard biofilm bacterial growth. This was shown to be due to the presence of the ions affecting bacterial membrane packing, aggregate packing and aggregate charge. The small monolayer pressure increase of the (+) α-TP bilayer planar island interactions suggested the antibacterial mechanism was not likely to be simple lyses, but perhaps internalisation and enzymatic inhibition. The (+) α-TP bilayer planar islands swelled into micron sized aggregates when dispersed in cell culture media, selectivity killed macrophages and selectively inhibited monocyte chemoattractant 1 production from human gingival fibroblast cells. The strategy of utilising phosphorylated vitamin E nanoaggregates as multifunctional agents in oral health described herein represents a potential technology platform worthy of clinical evaluation.

Topical nanomaterials can enhance the passive diffusion of therapeutic agents into biological tissues but the mechanism by which they function is not yet fully understood. The aim of this study was to elucidate the interactions between the model drug tetracaine and the surfaces of nanomaterials with the view to understand and optimise the transmembrane transport process. Tetracaine was observed to form aggregates in aqueous solutions in the μM range and this aggregation process changed its percutaneous permeation. Nanoparticles co-administered on the membrane surface upon drug application were shown to manipulate the drug aggregation, thereby enhancing transmembrane transport. Tetracaine adsorbed strongly to the surface of carboxylmodified polystyrene nanoparticles (NanoPSCOOH) and minimally to silica nanoparticles (NanoSiO₂ ). The NanoSiO₂ enhanced tetracaine transport by 3.6-fold while the NanoPSCOOH hindered tetracaine transport, leading to the conclusion that a mild perturbation of the tetracaine aggregation by a nanoparticle surface produced the most interesting effects in terms of transmembrane transport. These results were translated to a topical HPMC spray formulation. The co-administration of HPMC tetracaine spray formulation with NanoSiO₂ enhanced tetracaine transport by 95-fold, improved accumulative by 307-fold and reduced the lag time by 15.6-fold when compared to the commercially available Ametop. The superiority was attributed to the NanoSiO₂ breaking of tetracaine aggregates, known to hinder permeation. In addition, the decrease in formulation macroviscosity was hypothesized to have reduced drugvehicle interactions and thus facilitate permeation. The strategy of utilising nanomaterials to manipulate drug aggregation described herein represents a potential technology platform worthy of clinical evaluation.

Local barometric pressure changes at the apical surface of the skin have been reported to alter the mechanical and physiological properties of the cutaneous tissue. However, how skin changes induced by barometric pressure alter percutaneous penetration require further investigation. The aim of this study was to understand the effects of local barometric pressure changes upon cutaneous drug delivery with a view to understand if such an approach could be used to design a novel medicinal product. To accomplish this, one of the most widely used test systems for studying in vitro skin permeability, the Franz diffusion cell, was adapted to operate under sub-atmospheric pressure. Three relevant agents (tetracaine, diclofenac diethylamine and aciclovir) were selected, based upon their different physicochemical properties, and a suitable analytical method was developed for each molecule. The model agents were shown to aggregate in solution and the process of aggregation appeared to retard penetration into the skin. In vitro hypobaric driven delivery was shown to be an effective means to achieve ‘targeting’ of diclofenac diethylamine and aciclovir within the epidermal tissue after topical application of the aggregated agents. The calculated epidermal ‘targeting’ potential was 4 and 1.4 for each model agent, respectively. The mechanical and morphological changes in the hypobaric stressed skin showed that the ‘targeted’ drug deposition to the epidermal layer was accompanied by an enlargement of the follicular infundibula (p < 0.001), reduced corneocyte size (p < 0.001) and skin thinning (p < 0.05). These findings suggested that both enhanced follicular and passive stratum corneum transport played a role in the manner which hypobaric pressure improved cutaneous penetration. Local hypobaric stress application to the skin was also shown to induce a haemodynamic response (i.e. a significant increase in blood flow (p < 0.001)), which together with the ability to alter skin drug diffusion significantly enhanced cutaneous and systemic bioavailability (p < 0.01) of a model macromolecule. These results demonstrated that the application of topical barometric stress represented a promising technology to deliver molecules into the skin and it was thought worthy of further evaluation.

Tuberculosis is a contagious disease caused by Mycobacterium Tuberculosis and is recognised as a global public health emergency. New approaches are required to improve the chemotherapy of TB, in particular to target the reservoir of M. Tuberculosis that accumulates in alveolar macrophages and lung lesions. The aim of this thesis was to develop polymeric nanoparticle-loaded formulations for the delivery of rifampicin to the lungs. Poly (vinyl alcohol) nanospheres (NS) and nanocapsules (NC) were developed using a modified nanoprecipitation method. Both types of nanocarrier were spherical with a mean diameter of ca. 220 nm (NS) and 150 nm (NC). Rifampicin was successfully encapsulated with efficiencies of 29.3 ± 0.7% and 32.3 ± 0.3%, for NS and NCs, respectively. Methods for enhancing the stability and modifying the release of rifampicin were developed. The uptake of the PVA nanocarriers was studied in-vitro using the J774A.1 macrophage-like cell line. After 6 h incubation, the amount of rifampicin imported into macrophages by drug-loaded nanoparticles, containing 1000 μg/ml of drug, was twice (NC) or three times (NS) greater than that attained with rifampicin solution. The drug-loaded PVA nanoparticles were formulated into a powder for pulmonary administration by spray drying into lactose to yield spherical microspheres of ca. 2 μm diameter. The deposition studies of the spray dried powders, carried out using a modified twin stage impinger, showed that the NS-loaded-microspheres had a better deposition profile than the NC-loaded microspheres. This work generated novel PVA nanocarriers, demonstrated that they are effective in targeting rifampicin to macrophages and exemplified their formulation as an inhaled drug delivery system.