The thesis constitutes an investigation into the production of floating photocatalytic particles (FPP) as a low cost, low carbon footprint and chemical-free wastewater treatment. It is anticipated that this approach would be particularly attractive for developing countries where it could reduce incidences of disease and pollution. The particles were manufactured from cocoa butter (CB), and contained either photocatalytic nanoparticle titanium dioxide TiO2 (P25) or silver-doped TiO2 (0.5% w/w). The photocatalytic activity of the particles was evaluated by means of the decolourisation of the dye indigo carmine (IC). Three arrangements were used; small scale treatment using Petri dishes, an 1800 ml batch-recirculation photoreactor and an 8 litre UV contactor. Membrane emulsification (ME) was the technique used here to generate particles of controlled size. The particles were in effect what are known as Pickering emulsions in which the solid fat core (CB) was stabilised by TiO2 nanoparticles, resulting in composite particles that float easily and can receive incident light to generate highly reactive free radical species. The FPPs were characterised by FEGSEM and EDs mapping analysis, and the images obtained displayed a spherical structure with a rough outer surface, and the EDs showed a good coverage of TiO2 on the surface of at a maximum loading of 10% w/w. Tests were conducted to assess the stability of the particles when used in repeated cycles. Reuse of the particles caused a significant drop of photodegradation activity after four cycles to 42% of that of freshly prepared particles. The correlation of photocatalytic activity with silver dosage was also investigated. The highest photocatalytic activity was achieved at 0.5 wt. % of silver doped TiO2 and was some 10% greater than for un- doped particles. The organic carbon release resulted from TOC analysis for the FPPs that were exposed to UV light for 8.5 hr in water was less than 1 wt. %. First order reaction kinetics were exhibited during decolourisation of IC dye with respect to the initial dye concentration, radiation intensity, percentage coverage of the liquid surface by the FPPs, and the catalytic loading. For a static system (i.e. no forced convection), the most effective surface coverage was identified as being in the range of 60 to 80%. A linear source spherical emission model (LSSE) was adopted to estimate the intensity of the incident radiation on the surface of the FPP layer in the photoreactor and validated. In addition, a preliminary kinetic model to describe of the effect of the photocatalytic active surface concentration of TiO2 as well as the efficient intensity flux in the kinetic model was developed for the FPP layer photoreactor.

Enteric pathogens form a large part of infectious diseases which contribute to a bulk of the healthcare costs. Enteric infections are usually contracted via the faecal-oral route or through contact with contaminated surfaces. Treatment by antibiotics is becoming increasingly ineffective due to the growing number of antibiotic resistant strains. Anti-microbial resistance poses a serious threat to the future of healthcare worldwide and necessitates the search for alternate forms of therapy. Bacteriophages (phages), are viruses which specifically infect and lyse bacteria. To introduce phages as a viable form of therapy, route of administration needs to be considered carefully. Model phages with broad host ranges are ideal for therapy however oral delivery to the lower gastro-intestinal (GI) poses several challenges. The acidic stomach environment can be detrimental to phages, rendering them inactive during passage. To overcome this challenge and improve the stability of phage during encapsulation and storage, this PhD research has been conducted. pH responsive polymers, Eudragit and alginate were used to develop composite microparticles which protected phage from acidic pH (pH 1-3). A novel method of acidifying oil was developed for crosslinking droplets in vitro to avoid the use of harsh solvent systems that can cause phage inactivation. Platform microfluidic technology was employed for phage encapsulation for the first time. Monodispersed droplets and particles were produced, offering fine-tuning of droplet diameter to tailor the release and pH protection of encapsulated phage. Process scale-up was attempted using membrane emulsification (ME) to produce larger volumes of encapsulated phage. In vitro and in-situ models investigated the efficacy of encapsulated phage-bacterial killing. Industrial scale method of spray drying, and electrospinning were also used to demonstrate the versatility of the formulation. Tableting dry powder phage, showed an effective method for producing solid dosage forms for therapy. Additionally, electrospun phage fibres also showed the potential use of pH responsive formulations in addressing wound infections. Improvement in encapsulated phage storage stability was observed with the addition of trehalose in the formulation. This research underpins the need for testing phage encapsulation for site-specific delivery and offers insight into the potential use of commercially available technologies.

Microspheres (< 1000 μm) have applications in various fields (e.g., drug delivery, cosmetics, food, etc.). Microspheres can be generated by the micro-fluidic technique, in which microspheres are produced from one fluid under the action of another immiscible fluid in a network of channels. There are four performance indexes associated with a microsphere generation process with a device, namely (1) the size of microspheres (as small as possible), (2) the uniformity of size distributions (as high as possible), and (3) the flexibility of devices (i.e., the size range of microspheres that can be generated with one device), and (4) the efficacy of the microspheres generation process (mass production or not). Two operating principles along with their corresponding devices, the modified T-junction device and membrane emulsification device, are studied in this dissertation, because of their unique features, with the former having an excellent task flexibility and the latter having an excellent efficacy. The study defined three objectives, namely (1) understanding the mechanism of the microsphere generation process with the modified T-junction by both numerical investigation and experimental investigation, (2) optimizing the microsphere generation process with any micro-fluidic device in general and the modified T-junction device in particular (optimization: the size and uniformity), and (3) designing and fabricating a new emulsification membrane by tackling the shortcoming (i.e., fragile with the membrane) with the existing emulsification membrane. For objective (1), a simulation model was built first, validated by the experiment, and then the simulation model was employed to study the regimes. For objective (2), a new optimization procedure was first proposed for general micro-fluidic systems and then applied to the modified T-junction system. For objective (3), a new membrane was designed and fabricated and tested. The following conclusions can be drawn from the study: (1) the modified T-junction device works based on a combined operating principle (flow focusing and conventional T-junction) and there are three regimes (instead of the four regimes in the conventional T-junction) in the flow; (2) the optimization of the microsphere generation process makes sense for the micro-fluidic device in general and the modified T-junction in particular (the optimal modified T-junction is: the mean size: 16.1 μm and 24.8 μm, and the uniformity (Standard Deviation (SD)): 0.2 μm and 0.7 μm); (3) the shortcoming with emulsification membrane can be overcome with a multi-layer membrane architecture. There are several contributions made by this dissertation in the field of micro-fluidic. First is the provision of an accurate Computational Fluid Dynamics (CFD) model for the modified T-junction. Second is the new knowledge discovered regarding the mechanism of microsphere generation with the modified T-junction device. Third is the provision of an effective optimization approach for any micro-fluidic device in general and for the modified T-junction device in particular. Fourth is the design with the successful fabrication of the membrane emulsification device based on new system architecture (i.e., multi-layer structure). From an application’s perspective, this dissertation has provided evidence that with the micro-fluidic technique, the smallest size of microspheres can be 2.3 μm; the highest uniformity (SD) can be 0.8 μm. Further, if an application puts emphasis on the task flexibility, the modified T-junction device is an excellent choice, and if an application puts emphasis on the mass production, the multi-layer membrane device is an excellent choice.

Existing commercially available microcarriers are very efficient at encouraging cell attachment and proliferation. However, recovery of the cells is problematic as it requires the use of proteolytic enzymes which are damaging to critical cell adhesion proteins. From this perspective, temperature responsive polymers appear to be a valid option. The current innovative study is to produce and engineer microcarriers in terms of particle size, surface coating and properties, as well as thermo-responsiveness for cell release. All these benefits are based on particle production by membrane emulsification to provide a highly controlled particle size. The polymer of choice is poly N-isopropylacrylamide (pNIPAM) because of the sharpness of its phase transition, biocompatibility and transition temperature close to the physiological value. These characteristics make pNIPAM a very attractive material for Tissue Engineering applications. Cells are cultured on the hydrophobic surface at 37??C and can be readily detached without using proteolytic enzymes from the surface by lowering the temperature to room temperature. The Dispersion Cell (MicroPore Technologies Ltd, UK) was successfully employed for the production of W/O emulsions. The generated monomer droplets were additionally solidified by applying a free radical polymerisation to manufacture solid pNIPAM microspheres. Additionally, calcium alginate particles were also generated and further functionalised with amine terminated pNIPAM to form temperature responsive core-shell particles by simply taking advantage of the electrostatic interactions between the carboxyl groups of the alginate and amino groups of the modified pNIPAM. Controlled particle production was achieved by varying process parameters and changing the recipe formulation (e.g. monomer concentration, surfactant concentration, pore size and inter-pore spacing, injection rate, shear stress applied at the membrane s surface). The manufactured particles were then analysed in terms of particle size and size distribution, chemical composition, surface analysis, shrinkage ratio and thermo-responsiveness and further sterilised and used for cell culture and release experiments. Swiss Albino 3T3 fibroblastic cells (ATCC, USA) were utilised to show proof-of-concept for this technology. Cell attachment and proliferation were assessed and successfully demonstrated qualitatively and quantitatively. pNIPAM solid particles, uncoated and with different protein coatings were shown to allow a limited degree of cell attachment and proliferation compared to a commercially available microcarrier. On a different approach, uncoated core-shell structures demonstrated improved capabilities for cell attachment and proliferation, similar to commercially available microcarriers. Having in mind the potential of temperature responsive polymers and the aim of this innovative study, cell detachment from the generated microcarriers was evaluated and compared to a commercially available temperature responsive surface. Necessary time for detachment was recorded and detached cells were recovered and reseeded onto tissue culture plastic surfaces in order to evaluate the replating and reattachment capabilities of the recovered cells. Successful cell detachment was achieved when using the core-shell structures as cell microcarriers, but the necessary time of detachment was of an order higher than that for the commercial temperature responsive surface.

Les nanoémulsions sont des formulations intéressantes pour des applications telles que les cosmétiques, les produits pharmaceutiques et les produits alimentaires. Elles peuvent être produites par des techniques à basse ou haute énergie. Dans ce travail, un procédé impliquant une pression modérée, l'émulsification membranaire par prémix a été proposé comme alternative. Des nanoémulsions huile-dans-eau (H/E) et eau-dans-huile (E/H) ont été produites avec une installation à l'échelle pilote composée d'un pousse-seringue à haute pression et d'une membrane Shirasu Porous Glass (SPG). Tout d'abord, l'influence des nombreux paramètres de procédé et de composition sur la taille des gouttelettes et la pression résultante a été étudiée avec des compositions modèles afin d'optimiser la production. Ainsi, des nanoémulsions H/E d'environ 260 nm et E/H d'environ 600 nm ont été produites avec succès. Puis, le montage a été utilisé pour produire des nanoémulsions de compositions spécifiques, des nanoémulsions H/E et E/H stabilisées avec des tensioactifs polypeptidiques et une nanoémulsion H/E adaptée à l'injection. Enfin, le procédé développé a été comparé à deux procédés à haute énergie traditionnels, le microfludiseur et les ultrasons en termes de taille des gouttelettes et de conservation d'actifs. Aucune différence entre les procédés n'a été observée en ce qui concerne la préservation de l'acif choisi. Cependant, en ce qui concerne la taille, les nanoémulsions produites par les membranes ont présenté des gouttelettes monodisperses de 335 nm par rapport aux autres procédés qui ont produit des nanoémulsions d'environ 150 nm de taille moyenne mais contenant aussi des gouttelettes de taille micrométrique détectées par diffraction laser et microscopie optique. Pour cette raison, les nanoémulsions produites par procédé membranaire conviennent également pour des applications parentérales sans étape de filtration supplémentaire / Nanoemulsions are interesting carriers for applications such as cosmetics, pharmaceutical and food. They are produced usually by low or high energy techniques. In this work, a process involving moderate pressure, premix membrane emulsification (PME) was proposed as an alternative. Oil-in-water (O/W) and water-in-oil (W/O) nanoemulsions were produced with a pilot scale set-up composed of a controlled high pressure syringe pump and Shirasu Porous Glass (SPG) membrane. First, the influence of process and composition parameters on droplet sizes and pressures was extensively studied with model compositions to optimize the production. Thus, nanoemulsions down to 260 nm for O/W and around 600 nm for W/O were successfully produced. Then, the set-up was used to produce nanoemulsions of specific compositions: O/W and W/O nanoemulsions stabilized with polypeptidic surfactants and O/W nanoemulsions suitable for injection. Finally, the set-up developed was compared to two traditional high energy processes, microfludizer and ultrasound in terms of droplet size and active preservation. No real difference between the three processes was seen on active preservation with the model active chosen. However, regarding droplet size, PME produced monodispersed droplets of 335 nm compared to the other processes which produced nanoemulsions of around 150 nm but with the presence of micron size droplets detected by laser diffraction and optical microscopy. Therefore, PME nanoemulsions are also suitable for parenterals applications with no additional filtration step required

<p>Cilj ove doktorske disertacije je dobijanje vi&scaron;estrukih V₁/U/V₂ emulzija kao nosača aktivnih materija u dvostepenom postupku, pri čemu se za drugi korak pripreme koristi tehnika membranskog emulgovanja (ME), na membrani od sinterovanog stakla implementiranoj u ćeliju sa me&scaron;anjem. Proces ME koristi se u svrhu unapređenja karakteristika formiranih emulzija, u smislu bolje kontrole veličine i raspodele veličina formiranih kapi, koje mogu da dovedu do razlika u stepenu inkapsulacije aktivnih materija u unutra&scaron;njoj vodenoj fazi, u odnosu na proces u kome se za drugi korak pripreme emulzija koristi tehnika homogenizacije.<br />Kompletna optimizacija sastava V₁/U emulzija, koja obuhvata određivanje koncentracije hidrofobnog emulgatora (PGPR), lipofobne materije (NaCl) i tikvinog ulja kao sekundarne aktivne komponente, rezultirala je formiranjem stabilnih nanoemulzija sa pobolj&scaron;anim nutritivnim svojstvima. Nutritivno unapređeni emulzioni sistemi optimizovanog sastava kori&scaron;ćeni su za inkapsulaciju primarnih aktivnih komponenata (vodenog i etanolnog ekstrakata belog luka) u cilju za&scaron;tite bioaktivnih sastojaka i maskiranja neprijatnog mirisa i ukusa. Nakon definisanja sastava svih faza vi&scaron;estrukih emulzija, koje ukljuĉuje određivanje tipa hidrofilnog emulgatora i njegove koncentracije, kao i ispitivanja uticaja dodavanja osmotskog regulatora (glukoze) u spolja&scaron;nju vodenu fazu na stabilnost sistema i difuziju lipofoba, formirane su vi&scaron;estruke emulzije sa unetim aktivnim komponentama membranskim emulgovanjem u ćeliji sa me&scaron;anjem. Sistematiĉna karakterizacija membrane od sinter stakla kao ekonomski opravdanog membranskog materijala, dala je mogućnost njegove primene u procesu. Detaljno ispitivanje uticaja procesnih parametara (transmembranskog pritiska i brzine me&scaron;anja) i vi&scaron;ekriterijumska optimizacija procesa ME, dovela su do formiranja vi&scaron;estrukih emulzija sa užom raspodelom veličina kapi, koja je indirektno uticala i na pobolj&scaron;anje zadržavanja inkapsuliranog materijala u unutra&scaron;njosti emulzija tokom vremena, u odnosu na emulzije pripremljene u postupku homogenizacije.</p> / <p style="text-align: justify;">The aim of this doctoral thesis was to prepare multiple W/O/W emulsions with encapsulated active substances in both phases, by a two-step process, where the stirred cell membrane emulsification (ME) process, with a sintered glass filter disk as a membrane, was used as the second step, instead of conventional process (homogenization). The ME process was employed in order to improve the characteristics of the formed emulsions, in terms of better control of the size and droplet size distribution, that can change the encapsulation degree of active ingredients in the internal aqueous phase.<br />The complete optimization of W/O emulsion composition, which includes determination of optimal contents of a hydrophobic emulsifier (PGPR), a lipophobic substance (NaCl) and pumpkin seed oil as an active component of the oil phase, resulted in the formation of stable nanoemulsions with improved nutritional properties. This nutritionally enhanced emulsion was used to encapsulate primary active ingredients (aqueous and ethanol garlic extract), in order to protect instable bioactive compounds of the extracts and mask the unpleasant smell and taste. After defining the composition of all phases of multiple emulsions, which includes determination of a suitable hydrophilic emulsifier and its optimal content, as well as examining the effect of addition of an osmotic regulator (glucose) in the external aqueous phase on the emulsion stability and lipophobe diffusion, multiple emulsions with encapsulated active components were formed by membrane emulsification in the stirred cell. The complete characterization of the sintered glass as an economically favourable membrane material, gave the possibility of its application in the process. Investigation of the influence of process parameters (transmembrane pressure and impeller rotation speed) and multiobjective optimization of ME, led to the formation of the multiple emulsions with a narrow droplet size distribution, which had improved retention of encapsulated material in the internal water phase over time, relative to the emulsions prepared by the homogenization process.</p>

No / Microcarrier cell culture systems provide an attractive alternative to the conventional monolayer cell culture for cell amplification, due to their high surface area-to-volume ratio. Unlike enzymatic methods for removing cells from microcarriers after cell culture, which can lead to irreversible damage of the cells, microcarriers which release cells by temperature adjustment have been developed. This was achieved by grafting a temperature-responsive polymer, poly(N-isopropylacrylamide) (PNIPAAm), on the microcarrier surface. This review comprehensively presents various methods to prepare such thermo-responsive microcarriers based on PNIPAAm. These methods include the grafting-to technique, grafting-from technique, grafting-through technique, along with methods leading to PNIPAAm hydrogel beads, seeded polymerization, and non-covalent adsorption. The methods for controlling PNIPAAm grafting density, molecular weight and molecular architecture are also outlined. Further, the efficiency of cell attachment, proliferation and thermally-induced detachment of such thermo-responsive microcarriers is introduced and compared. (C) 2015 Elsevier Ltd. All rights reserved. / EPSRC