The introductory chapter of this doctoral thesis provides an overview of the salient properties of pharmaceutical excipients, chitin, metal silicates and sugar alcohols in order to give a scientific background/context to the research subject matter reported in subsequent chapter of the thesis. When chitin is used in pharmaceutical formulations processing of chitin with metal silicates is advantageous, from both an industrial and pharmaceutical perspective, compared to processing using silicon dioxide. Unlike the use of acidic and basic reagents for the industrial preparation of chitin-silica particles, co-precipitation of metal silicates is dependent upon a simple replacement reaction between sodium silicate and metal chlorides. When co-precipitated onto chitin particles, aluminum, magnesium, or calcium silicates result in non-hygroscopic, highly compactable, and disintegrable compacts. Disintegration and hardness parameters for co-processed chitin compacts were investigated and found to be independent of the particle size. Capillary action appears to be the major contributor to both water uptake and the driving force for disintegration of compacts. The good compaction and compression properties exhibited by the chitin–metal silicates were found to be strongly dependent upon the type of metal silicate co-precipitated onto chitin. In addition, the inherent binding and disintegration abilities of chitin–metal silicates are useful in pharmaceutical applications when poorly compressible and/or highly non-polar drugs need to be formulated. The influence of the lubricant magnesium stearate (MgSt) on the powder and tablet properties of chitin-Mg silicate co-precipitate was examined and compared with lubricated Avicel® 200 and Avicel-Mg silicate co-precipitate. Crushing strength and disintegration-time studies were conducted in order to evaluate tablet properties at different compression pressures. Lubrication of chitin-Mg silicate powder with MgSt was evaluated using a high speed rotary tablet press. The compactability and disintegration time of chitin-Mg silicate are unaffected by the possible deleterious action of up to 2% (w/w) MgSt. The deleterious effect of MgSt on Avicel® 200 compaction was found to be minimized when magnesium silicate was co-precipitated onto Avicel® 200. Lubrication of chitin-Mg silicate with MgSt does not enhance particle agglomeration, whereas the opposite is the case for Avicel® 200; the foregoing was ascertained by measurements of the fixed measured bulk density, constant powder porosity using Kawakita analysis and by the absence of variation in particle size distribution in the presence of up to 5% (w/w) MgSt. In the case of chitin-Mg silicate tablets the ejection force was greatly reduced at a compression speed of 150,000 tablet/h at a MgSt concentration of 0.5% (w/w) when compared with the unlubricated powder. The physical properties and drug dissolution profile of ibuprofen tablets were found to be unaffected when chitin-Mg silicate was lubricated up to 5% (w/w) with MgSt. Optimal drug dissolution was attained for gemfibrozil tablets using 3% (w/w) MgSt when compared to a reference (LOPID® tablets). A co-processed excipient was prepared from commercially available crystalline mannitol and -chitin using direct compression as well as spray, wet and dry granulation. The effect of the ratio of the two components, percentage of lubricant and particle size on the properties of the prepared co-processed excipient has been investigated. -Chitin forms non-hygroscopic, highly compactable, disintegrable compacts when co-processed with crystalline mannitol. The compaction properties of the co-processed mannitol-chitin mixture were found to be dependent upon the quantity of mannitol added to chitin, in addition to the granulation procedure used. Optimal physicochemical properties of the excipient, from a manufacturing perspective, were obtained using a co-processed mannitol-chitin (2:8 w/w) mixture prepared by wet granulation (Cop-MC). Disintegration time, crushing strength and friability of tablets produced by Cop-MC, using magnesium stearate as a lubricant, were found to be independent of the particle size of the prepared granules. The inherent binding and disintegration properties of the compressed Cop-MC are useful for the formulation of poorly compressible, low and high strength active pharmaceutical ingredients. The ability to co-process α-chitin with crystalline mannitol allows chitin to be used as a valuable industrial pharmaceutical excipient. The preparation and characterization of the performance of a novel excipient for use in the development of oro-dispersible tablets (ODT) has also been undertaken. The excipient consists of α-chitin and crystalline mannitol. The physical properties (disintegration and wetting times, crushing force and friability) of the ODTs produced depend on the ratio of chitin and mannitol, in addition to the processing techniques used for excipient preparation. The excipient with optimal physicochemical properties was obtained at a chitin: mannitol ratio of 2:8 (w/w) produced by roll compaction (Cop-CM). Differential scanning calorimetry (DSC), Fourier-transform infrared (FT-IR), X-ray powder diffraction (XRPD) and scanning electron microscope (SEM) techniques were used to characterize the Cop-CM, in addition to characterization of its powder and ODT dosage forms. The effect of particle size distribution of the Cop-CM was investigated and found to have no significant influence on the overall tablet physical properties. The compressibility parameter (a) for Cop-CM was calculated from a Kawakita plot and found to be significantly higher (0.661) than that of mannitol (0.576) due to the presence of the highly compressible chitin (0.818). Montelukast sodium and domperidone ODTs, produced using Cop-CM, displayed the required physicochemical properties. The exceptional binding, fast wetting and super-disintegration properties of Cop-CM, in comparison with commercially available co-processed ODT excipients, results in a unique multi-functional base which can successfully be used in the formulation of oro-dispersible and fast immediate release tablets.

Hot-melt extrusion (HME) is one of the most widely used technologies in the plastic, rubber and food industries and it has also been extensively explored and used in academia and the pharmaceutical industry over the last decade. This project aims to investigate the efficiency of hydrophilic polymers to enhance the dissolution rate of poorly water-soluble APIs processed by HME. Indomethacin (INM) and famotidine (FMT) were selected as model active substances while polyvinyl caprolactam graft copolymer, Soluplus® (SOL) and vinylpyrrolidone-vinyl acetate copolymer grades Kollidon® VA64 (VA64) and Plasdone® S630 (S630) were used as hydrophilic polymeric carriers. For the purpose of the study, all drug-polymer binary blends at various ratios were processed by a Randcastle single screw extruder. The physico-chemical properties and the morphology of the extrudates were evaluated via x-ray powder diffraction (XRPD), differential scanning calorimetry (DSC) and scanning electron microscopy (SEM). INM and FMT exhibited strong plasticization effects at specific concentrations and were found to be molecularly dispersed within the polymer blends. The in vitro dissolution studies showed increased INM/FMT release rates for all formulations compared to that of pure APIs alone. Ibuprofen was also embedded in a methacrylate copolymer (Eudragit® EPO) matrix to produce solid dispersions by hot-melt extrusion processing. The obtained granules were incorporated into orally disintegrating tablets (ODTs). The tablets were developed by varying the ratio of superdisintegrants such as sodium croscarmellose and cross-linked polyvinylpyrrolidone while a direct compression process was used to compress the ODTs under various compaction forces to optimize tablet robustness. The properties of the compressed tablets which included porosity, hardness, and friability and dissolution profiles were further evaluated and compared with commercially available Nurofen® Meltlet ODTs. In vitro dissolution of the extruded ODTs showed rapid release of ibuprofen compared to that of Nurofen® Meltlets. The in vitro and in vivo evaluation of the masking efficiency of hot melt extruded paracetamol (PMOL) formulations was examined. Extruded granules containing high PMOL loadings in Eudragit EPO® (EPO) or Kollidon® VA64 (VA64) were prepared by HME. Similarly propranolol HCl (PRP), diphenhydramine HCl (DPD), cetirizine HCl (CTZ) and verapamil HCl (VRP) were used as model cationic active substances while pH sensitive anionic methacrylic acid based methyl methacrylate coplolymers Eudragit® L100 (L100) and ethyl acrylate copolymer Eudragit® L100-55 (Acryl-EZE®) (L100-55) were used as polymeric carriers in order to produce taste masked extruded formulations determining drug-polymers intermolecular interactions. The taste masking effect of the processed formulation was evaluated in vivo by a panel of six healthy human volunteers. In addition, in vitro evaluation was carried out by an Astree e-tongue (Alpha MOS) equipped with seven sensors and Taste Sensing System TS5000Z (INSENT), respectively. The taste and sensory evaluation in human volunteers demonstrated that the formulation masked the bitter taste of the APIs and improved tablet palatability. In addition to that the taste sensing technology demonstrated taste improvement for all polymers by correlating the data obtained for the placebo polymers and the pure APIs alone. The e-tongue results were in good agreement with the in vivo evaluation. Molecular modelling (Gaussian 09) predicted the existence of two possible H-bonding types while Fourier Transform Infra-Red (FT-IR) and NMR studies confirmed drug-polymer interactions between the functional groups of both components (cationic drugs–anionic polymers). Furthermore, the intermolecular interactions evaluated by Flory-Huggins interaction parameters theory and X-ray photoelectron spectroscopy (XPS) showed stronger interactions between drug-polymer in L100 systems compared to that of L100-55 systems. The mechanism of the intermolecular interactions derived from this research showed the presence of H bonding between the amine group of the active substances and the carboxylic groups in the polymer. Hydrocortisone (HCS) was also embedded and extruded with ethyl cellulose N10 (EC N10) or ethyl cellulose Premium 7 (EC P7) in order to develop sustained release tablets processed by HME. The compressed tablets were subsequently coated with an enteric coating polymer, Eudragit® S100 (15-20%), which showed sustained release over 12 hrs with a lag time of 2 hrs. Further analysis of the release mechanism of HCS from tablets was performed by implementing five different kinetic release models which confirmed that the release of HCS from both coated and uncoated tablets followed a first order kinetic model.

The development of template directed synthesis towards the formation of interlocked architectures has allowed for the synthesis of a variety of rotaxanes. Chapter 1 covers the history of rotaxanes including their nomenclature and methods of formation. An overview of the intermolecular interactions used to facilitate the synthesis of these architectures is described and examples of template directed synthesis and properties of rotaxanes are discussed. In Chapter 2 the use of the Diels-Alder reaction towards formation of rotaxanes in a ‘threading followed by stoppering’ protocol is covered. The synthesis of [n]rotaxanes is described with secondary ammonium ions, a novel perimidine benzimidazole and bispyridinium binding templates integrated into threads. In Chapter 3 a novel binding template was developed, incorporating a triazole into a dibenzylammonium binding motif. Binding studies were carried out and [n]rotaxanes were synthesised using this motif with the groups Diels-Alder ‘threading followed by stoppering’ protocol. Chapter 4 discusses the modification of the DB24C8 macrocycle with the aim to enhance binding interactions with a variety of binding motifs. Two macrocycles were successfully synthesised and their binding affinities calculated with known and novel binding templates investigated in the previous chapters. The work in this thesis shows a Diels-Alder stoppering reaction can be successfully used to synthesise [n]rotaxanes with a variety of binding templates including novel templates discovered during this project. During the work it was also revealed that modifications to known binding templates can provide an enhancement in binding interactions in comparison to their unmodified predecessors.

Interest and employment of boron doped diamond (BDD) as an electrode material has grown rapidly over the last decade, due to its unique advantageous properties over traditional electrode materials. BDD has minimal background currents and can offer an increased potential range allowing for the detection of an increased range of analytes. Furthermore BDD stability in harsh conditions, elevated temperatures and pressures offers a wealth of applications. Polycrystalline BDD (pBDD) is commercially available in large wafers for industrial applications. This material is comparatively easy to grow when compared to single crystal BDD (scBDD) which requires careful homoepitaxial growth. This thesis aims to characterise scBDD grown with differing boron dopant densities, crystal orientation and growth procedures; with a view to determining the most suitable scBDD material for employment in electroanalytical applications. Characterisation is performed using high resolution microscopic and spectroscopic techniques which show sample variations relating to growth parameters. No non-diamond like carbon is detected and boron concentrations are all ~1020 cm-3 or greater. Electrochemical characterisation is performed using the scBDD in disc electrode format, where wide potential windows, minimal background currents and close to reversible behaviour is observed for outer sphere mediators FcTMA+/2+, IrCl6 2-/3- and Ru(NH3)6 3+/2+. Electrode pre-treatments demonstrate the importance of surface termination supporting faster or slower electron transfer kinetics of selected inner sphere mediators. scBDD was functionalised with gold nanoparticles to aid in sample homogeneity determination, highlighted some heterogeneities as a direct result of a failed growth process. This was performed at both macro and micro scales, giving rise to differing nucleation theories. Finally electrochemical imaging using scanning electrochemical microscopy is reported, enabling the determination of FcTMA+/2+ and Ru(NH3)6 3+/2+ kinetic electron transfer rates at well-defined tip-substrate distances.

This thesis was focussed toward providing new approaches to protein crystallization. Herein, we describe three new such approaches. Firstly, we describe proof-of-concept studies which demonstrate that simple DC electrochemical systems may be used to enhance and/or control the growth of lysozyme protein crystals on the surface of platinum disc electrodes. Secondly, we demonstrate how various oil/water interfaces provide both novel and unique environments for the study and enhancement of protein crystallization studies. In particular, we show how some oil/water interfaces greatly enhance the extent of lysozyme crystallization in comparison to the air/water interface whilst others do not. Thirdly, we show for the first time, that by application of small magnitude potentials to the ITIES, large increases in lysozyme crystal growth can be achieved (on the ITIES) in short time. Additionally, and unrelated to protein crystallization, we find that large potential-dependent changes in surface tension may be achieved by probable reversible adsorption/desorption of proteins to and from the oil-water interface. The reversible changes in droplet geometry are, in some cases, large and seem controllable. As such, this methodology warrants consideration as means to enhance the performance of alternative liquid/liquid ultra low-voltage and conventional electrowetting systems. The rapid crystallization of TBATPB at the ITIES is also reported for the first time. This work is of importance to theory and experiment regarding ion-transfer mechanisms at the ITIES. Additionally, this work may point towards a new type of crystallization technology for a variety of molecules grounded in methodology developed for liquid/liquid electrochemical systems.

Mass spectrometry (MS) is a powerful analytical technique used to characterize various compounds by measuring the mass-to-charge ratio (m/z). Among different types of mass analyzers, Fourier transform ion cyclotron resonance mass spectrometer (FT-ICR MS) is the instrument of choice for those working at the forefront of research, as it offers incomparable mass accuracy, resolving power, and the highest flexibility for hybrid instrumentation and fragmentation techniques. The FT-ICR MS requires professional and careful tuning to achieve its superior performance. Our work aims to review, develop and apply advanced methods to improve the data quality of FT-ICR and push the limits of the instrument. FT-ICR spectrometry has been limited to the magnitude-mode for 40 years due to the complexity of the phase-wrapping problem. However, it is well known that by correcting phase of the data, the spectrum can be plotted in the absorption-mode with a mass resolving power that is as much as two times higher than conventional magnitude-mode. Based on the assumption that the frequency sweep excitation produces a quadratic accumulation in an ion’s phase value, a robust manual method to correct all ions’ phase shifts has been developed, which allows a broadband FT-ICR spectrum to be plotted in the absorption-mode. The developed phasing method has then been applied to a large variety of samples (peptides, proteins, crude oil), different spectral acquisition-mode (broadband, narrowband), and different design of ICR cells (Infinity cell, ParaCell) to compare the performance with the conventional magnitude-mode spectra. The outcome shows that, by plotting the absorption-mode spectrum, not only is the spectral quality improved at no extra cost, but the number of detectable peaks is also increased. Additionally, it has been found that artifactual peaks, such as noise or harmonics in the spectrum can be diagnosed immediately in the absorption-mode. Given the improved characteristics of the absorption-mode spectrum, the following research was then focused on a data processing procedure for phase correction and the features of the phase function. The results demonstrate that in the vast majority of cases, the phase function needs to be calculated just once, whenever the instrument is calibrated. In addition, an internal calibration method for calculating the phase function of spectra with insufficient peak density across the whole mass range has been developed. The above research is the basis of the Autophaser program which allows spectra recorded on any FT-ICR MS to be phase corrected in an automated manner.

The application of tetradentate aminoalcohol ligands to the KOtBu-catalysed hydrogenation of benzophenone has been studied. Hydrogenation was found to proceed via a transfer hydrogenation process with the ligands acting as hydrogen donors. A series of bidentate and tetradentate ligands containing a variety of coordinating groups including amino, hydroxy, silyl, phosphine and amido functionalities have been prepared and applied to the transition metal-catalysed asymmetric transfer hydrogenation of ketones using iron, ruthenium and rhodium metals although none were found to be enantioselective for the hydrogenation of acetophenone. A series of asymmetric tethered ruthenium half sandwich complexes have been applied to the asymmetric pressure hydrogenation of ketones. Studies have investigated the effect of changing the sulfonamide group, halide and tether length on the activity of the catalysts. The application of an achiral tethered ruthenium half sandwich complex as a catalyst for the pressure hydrogenation of aldehydes is also reported. A novel synthesis of tethered ruthenium complexes using aryl substitution methodology has been developed and applied to the preparation of a series of novel complexes which were found to be highly active for asymmetric pressure hydrogenation of ketones. The application of the synthesis to the preparation of poly(methyl methacrylate) supported complexes is also discussed. Application of the supported catalysts to asymmetric pressure and transfer hydrogenation of acetophenone has shown potential for the development of an active heterogeneous catalyst for transfer hydrogenation of ketones in aqueous media.

In this project, the asymmetric pressure and transfer hydrogenation of a number of substrates was carried out in attempt to asymmetrically form 5-substituted 6- membered saturated heterocycles, directly applicable to the asymmetric synthesis of (-)-cytisine and other related compounds. The hydrogenation of N-acylaminoacrylate- like enamide 1 was successful, resulting in the formation of 5- substituted glutarimide 218 in up to 94 % ee. Unfortunately, subsequent reduction resulted in epimerisation and loss of ee, preventing an asymmetric synthesis of (-)- cytisine precursor 5. The asymmetric reduction of pyridones 2 and 3 (featuring proximal coordinating groups) did not proceed with any enantioselectivity; however, the racemic reduction products were successfully utilised in novel syntheses of cytisine precursor 5 and bispiperidine 6 respectively. The ATH of pyridyl methyl ketone 4 with (R,R)-RutethTsDPEN, (R,R)-248 resulted in the formation of pyridyl alcohol 303 in 78-83 % ee. This compound was converted to diastereomers (D1)-7a and (D2)-7b which are derivates of a cytisine precursor and other therapeutic targets.

This thesis explores the use of the tetrazine–norbornene inverse electron demand Diels-Alder cycloaddition reaction in polymer and materials science. Chapter 1 gives an introduction to the main concepts and techniques used throughout the thesis. Chapter 2 applies the tetrazine–norbornene reaction to polymer endfunctionalisation and polymer–polymer coupling, in both organic media and water, and establishes the methods (UV/vis and 1H NMR spectroscopies) for monitoring the coupling reaction. Chapter 3 applies the reaction to the modification of a self-assembled polymer micelle and demonstrates its use in tandem with the coppercatalysed azide–alkyne click reaction. The synthesis of an amphiphile bearing both norbornene and alkyne groups is described, the amphiphile is self-assembled and a one-pot dual functionalisation of both the core and shell carried out. Chapter 4 describes the formation and analysis by a variety of methods of sub-20 nm sized polystyrene nanoparticles through the single chain collapse of a norbornene-decorated polymer, ligated with a bisfunctional tetrazine. Chapter 5 discusses attempts to further expand the use of the reaction of tetrazines to polymers bearing pendent alkene groups. The synthesis and characterisation of such polymers is detailed, and attempts to functionalise with a variety of tetrazines described.

The use of reversible addition–fragmentation chain transfer (RAFT) polymerisation for the production of DNA–polymer conjugates is explored. Chapter 1 gives a general introduction to the field of DNA–polymer conjugates, their potential applications and methods for their synthesis. The need for a general, solutionphase technique for DNA–polymer conjugation is highlighted. In Chapters 2-5, the use of a number of different strategies for the production of DNA–polymer conjugates is described. Amide coupling (Chapter 2) is found to produce the desired products only under very specific reaction conditions. The thiol–alkene Michael addition reaction (Chapter 3) is found to afford DNA–polymer conjugates in aqueous solution with high yield; however, attempts to replicate this using organic solvents are not successful. The inverse electron-demand Diels–Alder reaction between tetrazine and norbornene (Chapter 4) is explored and found to produce DNA–polymer conjugates in high yield in organic solvents; however, the precursor compounds are time-consuming to prepare and so the generality of this approach is limited. Finally, the copper-catalysed azide–alkyne cycloaddition (Chapter 5) is found to be an excellent method for the production of a wide range of DNA–polymer conjugates. Chapter 6 describes the use of the DNA segment of a DNA–polymer conjugate to assemble a discrete three dimensional nanostructure – a DNA tetrahedron – incorporating the temperature-responsive polymer poly(N-isopropylacrylamide). These hybrid structures are found to be able to stabilise the formation of discrete, well-defined polymer nanoparticles at elevated temperatures. Chapter 7 describes the use of a non-covalent interaction (intercalation) to produce DNA– polymer conjugates. The effect of polymer molecular weight and structure on the strength of this interaction are explored. Finally, intercalation is exploited to template the formation of discrete polymer particles on a DNA strand.